Among them, CH4, C2H6, C3H8 and C4H10 are main carbon species. All carbon species, except for C1-C4 alkanes and alcohols, occur in negligible amounts in the fluids generated in systems with low H2O, but С15-С18 alkanes are slightly higher and oxygenated hydrocarbons are more diverse at higher temperatures and H2O concentrations. At a higher oxygen fugacity of +2.5 Δlog fO2 (IW), the fluids almost lack methane and contain about 1 rel.% C2-C4 alkanes, as well as fractions of percent of C15–18 alkanes and notable contents of alcohols and carboxylic acids. Methanimine (CH3N) is inferred to be the main nitrogen species in N-poor reduced fluids. Therefore, the behaviour of CH3N may control the nitrogen cycle in N-poor peridotitic mantle. Oxidation of fluids strongly reduces the concentration of CH4 and bulk carbon. However, higher alkanes, alcohols, and carboxylic acids can resist oxidation and should remain stable in mantle hydrous magmas.Deep carbon and nitrogen cycles played a critical role in the evolution of the Earth. Here we report on successful studying of speciation in C-O-H-N systems with low nitrogen contents at 6.3 GPa and 1100 to 1400 °C. At  There is a wealth of evidence for the existence of hydrocarbons in the mantle. Namely, Sugisaki and Mimura  sublithospheric diamonds reported by Smith et al. (ref. Abiotic hydrocarbons (HCs) and ammonia have been important agents in the Earth’s carbon and nitrogen cycles. Their stability in different tectonic settings in the course of geodynamic evolution could control the habitability of the planet, the amounts of carbon and nitrogen migrating in fluids, the processes of redox melting and freezing, and the formation of diamondsura ref.  studied al. ref. .7. The contribution of two former sources may be, however, limited: HCs may oxidise during subduction and can hardly survive the high impact temperatures. The composition of hydrocarbons may vary. For instance, HCs heavier than methane were inferred17 to be energetically favoured at the deep mantle P-T conditions. As for nitrogen in reduced mantle, there is a consensus that most of it resides in ammonia and NH4+ which substitutes for alkali cations in phengite, Cr-bearing clinopyroxene and other silicates19.The genesis of hydrocarbons in the mantle remains unclear. They might be a mixture of HCs which were recycled or delivered by meteorites and comets to the early  Earth, or synthesised by the Fischer-Tropsch reactionfO2). Estimates for continental lithospheric mantle (CLM) within the Kaapvaal20, Slave21 and Siberian23 cratons show that fO2 generally decreases depthward from +1 Δlog fO2 FMQ  at 100 km (~3.2 GPa) to -4 Δlog fO2 FMQ at a depth of 220 km (~7 GPa). The fO2 values at the CLM base about 200 km below the surface may vary from IW + 1 to IW + 3 log units1 and the temperatures at this depth may range within 1100–1400 °С23. According to thermodynamic calculations, lower alkanes  and ammonia are expected to be stable under fO2 conditions of the CLM26, but they almost disappear from fluids at fO2 reaching CW (the maximum H2O content in C-O-H fluids). Moreover, the silicate environment can influence the pH of deep H2O-bearing fluids and thus the carbon and nitrogen speciation27.The behaviour of carbon and nitrogen species in mantle fluids depends on oxygen fugacity  and agree well with calculations32. The concentrations of lower alkanes at pressures from 4 to 7 GPa and typical CLM temperatures33 vary only little, but the precise contents of other hydrocarbons remain unknown. Among nitrogen species, ammonia was reported3 to predominate in nitrogen rich N-O-H fluids entrapped in quartz and olivine at 0.2–3.5 GPa, 600–1400 °C and fO2 at the Fe-FeO equilibrium, as well as in ultra-reduced nitrogen-rich C-O-H-N fluids at 5.5–7.8 GPa and 1100–1500 °C, as shown by our recent experiments34. In upper mantle aqueous fluids under reducing conditions, nitrogen is expected to occur mainly as ammonium (NH4+)26.Recent decades have brought much progress in experimental techniques with fO2 about or slightly below IW corresponding to the conditions at the СLM base (~200 km depth) near the boundary with the asthenosphere, and (ii) the relative stability of HCs and N-bearing compounds at fO2 IW +2.5 log units corresponding to reactions of reduced C-O-H-N fluids with oxidised lithosphere. The estimates33 that the fluid composition does not depend much on pressure within 4–7 GPa allows us to extrapolate the results onto the upper mantle pressure range.In this study we apply quenching experiments with buffered hydrogen fugacity to study (i) the stability of different carbon and nitrogen species in N-poor C-O-H-N fluids at 6.3 GPa, 1100–1400 °C and fO229. The potential effect was monitored against concentration changes of species involved in the C2H6 + H2 → 2CH4 reaction, and back reactions were shown to stop completely only at relatively rapid cooling of 120 deg/s. The fluids cooling at slower rates contained less hydrogen (2 to 4 mol.%) and, correspondingly, more CH4. The closure temperature for the C-O-H system equilibration was suggested to be <800 °C29. Earlier we31 investigated the effect of cooling rates in the range of 1 to 200 deg/s on the composition of C-O-H fluids synthesised at 6.3 GPa and 1600 °C in 15 hr-long runs. Comparison of fluids generated from the same starting materials but cooled at different rates showed CH4 and C2H6 to increase from 2–3 to 9–10 mole % and from 1 to 3 mole %, respectively, as cooling slowed down from 200 to 27 deg/s. Further deceleration to 1 deg/s did not change the concentration of CH4, but led to C2H6 increase from 3 to 4–5 mol.%. Therefore, synthesis of hydrocarbons most likely was due to back reactions of hydrogen with graphite during slow cooling, as we suggested31. Meanwhile, the changes of nitrogen speciation in O-H-N fluids at cooling rates from 70 to 140 deg/s in the forward and reversal experiments of Li and Keppler  and formation of minor amounts (within ~0.5 rel.%) of olefins, arenes, and oxygenated hydrocarbons: aldehydes, ketones, and carboxylic acids . Note especially that slow cooling resulted in the formation of more methanimine (CH3N), at the same P-T-τ conditions as during quenching  slightly at 6.3 GPa, while the ratios of CH4 to C2H6, C3H8 and C4H10 at high and low cooling rates scatter within a reasonable error. However, slow cooling fluids obtained in this study are remarkable by higher concentrations of species that trace the back reactions . Thus, our and published data, including our previous results for 6.3 GPa and 1600 °C31, indicate that only cooling from 1100–1400 °C to room temperature at a rate of 200 deg/s can be interpreted as quenching. Note that only quenching can provide reliable molecular compositions of fluids at the P–T conditions of the experiments.Therefore, back reactions in slowly cooling C-O-H-N fluids have different directions at the pressures 2.4 GPa and 6.3 GPa. Cooling leads mainly to synthesis of CH4/C2H6, CH4/C3H8 and CH4/C4H10 ratios of normalised peak areas at longer durations, irrespective of the starting charge composition , though remained below the level of the 1-min run  in the shortest run, but their concentrations became similar (CH4/C2H6 = 1.14) and commensurate with those at 1400 °C at the 7 hr duration. The quenched fluids obtained in 7-hr runs at 1100 °C almost lacked oxygenated hydrocarbons, except for some alcohols and ethers and furans. This data shows that the C-O-H-N fluids resulting from thermal decomposition of higher alkanes at 6.3 GPa and 1400 °C can attain equilibrium already in 2-hr runs, while the attainment of equilibrium at 1100 °C most likely requires at least 7-hr durations. Interestingly, alkanes reached equilibrium concentrations in 1 min at 1400 °C, while fluids synthesised in 1-min long runs at 1100 °C were very rich in ethane.At 1100 °C, the concentrations of main alkanes and the diversity of oxygenated hydrocarbons in C-O-H-N fluids differed notably in the shortest (1-min) and 7-hour long runs Tables –4. Note 2O from <1 to 11.2 rel.% . Note that the chosen fH2 buffering technique provided Fe3+ to Fe0 reduction in a 10-hr test run  to be the predominant nitrogen host in N-poor C-O-H-N fluids. However, N2 was persistent, though minor (0.1 to 0.01 rel.%), even in ultra-reduced C-O-H-N fluids resulting from decomposition of docosane, with the CH3N/N2 > 2 ratio in all cases. Ammonia appeared in a single 1-min run at 1400 °С, with its concentration notably exceeding both N2 and CH3N. Other nitrogen species were detectable in trace amounts .Synthesis in Pt capsules at 1100  and 1300 °С gave fluids with Cly Table . The res3N) was the main nitrogen species of C-O-H-N fluids at high-H2O as well /A(28 m/z) ≫ 1 in most of analysed spectra. Methanimine predominated in the fluids from both Au and Pt capsules. It was found in small amounts only in four runs with Pt capsules . Note that the concentration of CH3N increased at slow cooling  exhibited no distinct trends  in two unbuffered runs at 1200 and 1400 °С Table  because nt Table  while thfO2) is the key parameter of fluid systems against which to compare the compositions of fluids synthesised in quenching experiments with data on natural mantle fluids. fO2 in the experimental samples was calculated by Gibbs energy minimisation at 6.3 GPa and 1100–1400 °C knowing the components of the obtained fluids. However, chromatography–mass spectrometry revealed more than 30 carbon and nitrogen species in the fluids, and the calculations required some assumptions. Primarily, the presence of nitrogen species found in very low concentrations was neglected, i.e., the C-O-H-N system was reduced to the C-O-H one. The contribution of alkanes higher than C5, as well as oxygenated hydrocarbons and CO2, all below 1 rel.%, into the fO2 of the system was likewise assumed negligible. With these assumptions, the system composition was simplified to H2O, CH4, C2H6, C3H8, and C4H10, and this limited number of main species was used in CG-MS calibrations (see Supplementary information). The normalised peak areas of particular components were converted to mole % only for a part of quenching experiments where equilibrium concentrations of the main components were obtained. They were further used to estimate C contents in the fluids as a function of temperature at constant fO2 and as a function of fO2 at a constant temperature of 1400 °C  impedes this process by shifting the equilibrium toward the reagents. For this reason, ethane does not contribute to the formation of methyl/ethyl radicals and, hence, methane and higher HCs, and tends to accumulate. Nevertheless, the catalytic fission of n-butane produces two ethyl radicals that recombine and react with alkenes with further formation of higher HCs.The fluids generated in Au and Pt capsules differ in carbon speciation irrespective of run duration and temperature: methane is one of major fluid components  in both cases but the methane/ethane ratios of normalised peak areas are, respectively, CHfO2 Fig. . The 7-hThe fluids generated in both Au and Pt capsules contained various oxygen-bearing compounds, mainly alcohols, ethers, aldehydes, ketones and furans Tables . However4, C2H6, C3H8 and C4H10, and their concentrations  agree well with the calculated relations of CH4 > C2H6 > C3H8 > C4H1033 almost in all cases  and fO2 (2.5 log units above IW) at 6.3 GPa  at a constant oxygen fugacity of −log(fO2) = 11.Main carbon species in the synthesised equilibrium fluids are CHses Fig. . The CH4GPa Fig. . Taking rry Fig. . Previoual. ref.  for 5.0 15-С18 alkanes, alcohols, aldehydes, ketones, carboxyl acids, and furans . The effect of lower temperature (1200 °C instead of 1400 °C) is to reduce the diversity of alkanes and oxygenated hydrocarbons in more reduced fluids. As H2O exceeds 90 mole % and fO2 reaches 2.5 log units above IW, methane in the fluid almost zeroes down, while higher alkanes do not change much  cooling  but to cause almost no effect on C3, C4 and C5 alkanes , performed without external fH2 buffering31, oxidation of the C-O-H system produced an aqueous fluid with trace amounts of CH4 (0.5 to 0.7 mole%) and C2H6 (≤0.1 mol.%). According to the data of this study, hydrous silicate magmas generated within multiple redox fronts can entrap minor amounts of some higher alkanes and oxygenated hydrocarbons of mantle origin and carry them further to shallow mantle.The question whether any hydrocarbons can survive transport across the mantle redox fronts is essential for understanding the deep carbon cycle. Neither the stability of higher alkanes at 23, Stachel and Luth (ref. fO2 ∼IW to 1100 °С at fO2 slightly above IW are inferred to loose carbon (decreasing from 18 to 3 mole %) but gain water   Fig.  in the c45. The reaction of hydrocarbons with O2 at multiple redox fronts24 stimulates the activity of H2O and causes drastic reduction of total carbon content in the fluids, as well as rapid drop in the solidus temperature of the ambient rocks. The redox melting is considered to be an important process in the cratonic mantle lithosphere24. As a result of oxidation, carbon of methane and other hydrocarbons is inferred to release in the form of C0 and to become consumed for saturation with the aqueous fluid. Experimental data show that this C0 could be involved in diamond crystallisation. The chemistry of mineral inclusions in diamond47 and stable isotope data of carbon and nitrogen48 indicate distinct possibility of diamond precipitation from CH4. Higher alkanes and some oxygenated hydrocarbons have been shown experimentally to be stable against oxidation of hydrocarbon fluids till the water maximum  is the main nitrogen species in the studied fluids, but it loses importance (CH3N/N2 < 1) at a lower temperature of 1100 °C at constant fO2 in the system IW-2.5 log units; CH3N almost disappears while N2 becomes the predominant species as fO2 decreases to IW + 2.5 log units at 1400 °C.The carbon and nitrogen speciation in the equilibrium fluids depends on temperature and redox conditions. The CH3N species can strongly control the mantle nitrogen cycle, especially in N-poor fluids equilibrated with peridotite. Specifically, silicate phases capable of dissolving ammonia in the presence of NH3-bearing fluids hardly can be nitrogen hosts in equilibrium with CH3N-bearing fluids. Oxidation of peridotitic fluids with small N contents upon interaction with multiple redox fronts is inferred to decrease strongly the concentrations of methane and methanimine and slightly reduce the amount of ethane, but it causes significant changes neither to C3, C4 and C5 alkanes nor to C15-C19 alkanes and oxygenated hyrocarbons. As a result, hydrous magma can capture species stable to oxidation, as well as N2, which can be involved in diamond formation and carried to shallow mantle.The behaviour of the CH22H46) and stearic acid (С18Н36O2), and 99.9999% pure natural graphite . The efficiency of the chosen fH2 buffering technique has been proven in special tests (Supplementary Figs Starting mixtures for generation of carbon- and nitrogen-bearing fluids consisted of chemical-grade docosane (Cic acid С8Н36O2, aic acid С8Н36O2, aic acid С8Н36O2, aSupplementary informationRelated Manuscript File


Primary outcomes were differences in peripheral iron levels in children with ADHD versus healthy controls (HCs) and the severity of ADHD symptoms in children with/without ID (Hedges’ g) and the pooled adjusted odds ratio (OR) of the association between ADHD and ID. Overall, seventeen articles met the inclusion criteria. Peripheral serum ferritin levels were significantly lower in ADHD children , but no significant difference in serum iron or transferrin levels. In addition, the severity of ADHD was significantly higher in the children with ID than those without ID , and there was a significant association between ADHD and ID . Our results suggest that ADHD is associated with lower serum ferritin levels and ID. Future longitudinal studies are required to confirm these associations and to elucidate potential mechanisms.There is growing recognition that the risk of attention-deficit hyperactivity disorder (ADHD) in children may be influenced by micronutrient deficiencies, including iron. We conducted this meta-analysis to examine the association between ADHD and iron levels/iron deficiency (ID). We searched for the databases of the PubMed, ScienceDirect, Cochrane CENTRAL, and ClinicalTrials.gov up to August 9 ADHD can cause considerable disability and impaired quality of life2. Furthermore, children with ADHD also suffer from a high prevalence of co-occurring medical and psychiatric conditions such as depressive disorder, anxiety disorder, restless leg syndrome, enuresis, and serious stomach problems3.Attention-deficit hyperactivity disorder (ADHD) is a common neurodevelopmental condition with an estimated global prevalence of 7.2%4. While the pathophysiology of ADHD is still not entirely understood, dysregulated dopaminergic neuronal development in the prefrontal cortex and subcortical regions is believed to play a role based on research derived from neuroimaging studies and the effects of pharmacotherapeutic treatment5. Recently, the potential effect of environmental (non-genetic) factors has attracted attention in the etiology of ADHD6. Environmental factors are potentially modifiable and may represent preventable targets for these disorders, in addition to potentially providing novel therapies for certain aspects of ADHD, such as iron supplementation7. Among environmental risk factors, nutritional factors including certain micronutrient deficiencies have been increasingly implicated as possible risk factors for ADHD8.ADHD is currently thought to be a predominantly heritable condition, with genetic polymorphisms of dopamine receptors and dopamine transporters playing an important role9. Iron is stored safely in the body via binding to ferritin, which prevents the degrading effects of free iron. Iron is very important for early brain development and is required for normal myelination and neurotransmitter function. Evidence has shown that impaired iron absorption and subsequent iron deficiency (ID) in both the prenatal and postnatal periods may impair neurodevelopment, with long-lasting and possibly irreversible consequences10. In addition, ID may result in myelinating and/or synaptogenesis dysregulation11. Moreover, ID may be associated with impaired monoamine synthesis, resulting in dysregulated monoamine signal transduction12. Adequate iron intake and peripheral iron levels may therefore be important factors modifying the onset of ADHD or ameliorating the severity of ADHD13.Iron helps in homeostasis of the hemoglobin structure, antioxidants, genetic repair, and in particular central nervous system (CNS) function16. While helpful, two of these meta-analyses only considered peripheral ferritin levels. This limitation may have resulted in confounding effects, since peripheral ferritin levels can be affected by various factors including infection, inflammation, and oxidative stress and, therefore, may not represent the whole picture of iron storage in clinical practice17. In the most recent meta-analysis, Wang et al. updated the evidence of the relationship between iron and ADHD, and revealed significantly lower serum ferritin levels in children with ADHD than in controls (standardized mean difference (SMD) = −0.40, 95% CI = −0.66 to −0.14) but not serum iron 16. Based on this insignificant result of serum iron in ADHD and controls, the relationship between iron and ADHD still remained unclear. Furthermore, that recent meta-analysis did not provide information about other parameters of iron status such as transferrin level16. Furthermore, no previous study has investigated the relationship between the diagnosis of ID and the risk or severity of ADHD. Although the use of medications for ADHD has been well-established, certain side effects such as poor appetite may still limit their use18. Several studies have investigated the use of iron supplements for patients with ADHD with mixed results, however none of these studies specifically targeted patients with a diagnosis of ID19. In addition, two previous meta-analyses found lower ferritin level in patients with ADHD, however it is unclear whether such lower ferritin levels in patients with ADHD reaches a clinical diagnosis of ID15. Therefore, investigating the relationship between a diagnosis of ID and the risk and severity of ADHD may help to identify potential treatments such as iron supplementation.To date, three meta-analyses have evaluated peripheral iron levels, either in forms of iron or ferritin, in children with ADHDThe aim of the current study was to conduct an updated systematic review and meta-analysis considering differences in peripheral iron levels and all parameters of iron status between children with ADHD and healthy (asymptomatic) controls (HCs). In addition, we also aimed to explore the association between a diagnosis of ID and the risk and severity of ADHD.23. Finally, we recruited seventeen studies in our meta-analysis39, and the details are summarized in Table Figure Of the included studies, thirteen provided information about serum ferritin levels, six about serum iron levels, two about serum transferrin levels, three about the severity of ADHD symptoms in patients with ID compared to controls, and three provided data of adjusted odds ratios (ORs) with regards the association between ADHD and ID.9. Rather, we chose differences in the severity of ADHD symptoms in children with and without ID to indicate the presence of ADHD.We were unable to conduct meta-analysis for the prevalence of ADHD in children with and without ID because we did not have enough studies (n < 3)40 for case-control trials in subgroup meta-analysis of comparisons of the peripheral iron levels in children with and without ADHD was 6.82  with a standard deviation (SD) of 1.1741. The NOS score for cross-sectional trials in subgroup meta-analysis of comparisons of the peripheral iron levels in children with and without ADHD was 4.67  (SD = 0.58)41. In addition, the average modified NOS scores for cohort trials and cross-sectional trials in subgroup meta-analysis of comparisons of the severity of ADHD symptoms in children with and without iron deficiency were 5.00  (SD = 1.41)40 and 5.75  (SD = 2.50)41, respectively  score42  = −0.440 to −0.051, p = 0.013)  but not publication bias according to Egger’s regression test . The significance of the results did not change after sensitivity analysis with the removal of one study. However, meta-analysis could not be performed on plasma ferritin or peripheral blood ferritin levels because there were fewer than three datasets.Overall, the meta-analysis results demonstrated that the peripheral serum ferritin level in the children with ADHD  was significantly lower than in the children without ADHD 13) Fig. . There wk = 17, p = 0.025) but not significantly moderated by proportion of females (p = 0.061), percentage of combined subtypes of ADHD (p = 0.550), percentage of the inattention subtype of ADHD (p = 0.860), percentage of the hyperactivity/impulsivity subtype of ADHD (p = 0.884), cognition (in forms of mean IQ) (p = 0.574), sample size of the group (p = 0.740), and geographical latitude of where the study was conducted (p = 0.690) .To identify potential sources of heterogeneity, we focused on the studies recruiting children who did not receive medications. Three studies with four datasets were included42   but no significant publication bias according to the funnel plot 27.Meta-analysis demonstrated that the serum iron level in children with ADHD  was not significantly different from the children without ADHD 69) Fig. . There wp = 0.827), proportion of females (p = 0.958), sample size of the ADHD group (p = 0.388), and geographical latitude of where the study was conducted (p = 0.361)   or publication bias according to the funnel plot 36. We could not perform meta-analysis on plasma transferrin or peripheral blood transferrin levels because there were fewer than three datasets.Meta-analysis demonstrated that there was no significant difference in serum transferrin level between the children with  and without ADHD 96) Fig. . There wMeta-regression and subgroup meta-analysis could not be performed as fewer than the minimal number of datasets were available.31    or publication bias via inspection of the funnel plot 30 or Fuglestad, A. J. (2013) 31.The severity of ADHD symptoms was significantly higher in the children with ID than in those without ID02) Fig.  without Meta-regression and subgroup meta-analysis could not be performed as fewer than the minimal number of datasets were available.39   and publication bias via inspection of the funnel plot 26, the female subjects in the study by Chen, M. H. (2013) 9, or the male subjects in the study by Chen, M. H. (2013) 9. Meta-regression and subgroup meta-analysis could not be performed as fewer than the minimal number of datasets were available.The meta-analysis of the pooled adjusted OR for the association between ADHD and ID revealed a significant association between ADHD and ID31) Fig.  with sigThe main results of our review and meta-analysis suggest that serum ferritin levels, but not iron or transferrin levels, are significantly lower in children diagnosed with ADHD than in those without ADHD. However, when removal of one potential confounding study, the result of meta-analysis of serum iron changed into significantly lower serum iron level in the children with ADHD compared to the controls. Children with ID were also more likely to have ADHD and have more severe ADHD symptoms than those without ID.16 , we identified several significantly different baseline variables between the ADHD and control groups, including higher food iron intake and higher food vitamin C intake in the ADHD group. Vitamin C is known to enhance iron absorption from food43. Knowing that human iron nutrients primarily come from food intake, the children with ADHD included in the study by Chen who had significantly higher iron and vitamin C intake would be expected to show elevated blood iron levels. Such information about food intake was not provided by the other studies included in our subgroup meta-analysis of serum iron levels38. Therefore, it was reasonable to exclude data from the study by Chen et al.27 when interpreting the results of subgroup meta-analysis of serum iron levels. Following exclusion from this study, the results of subgroup meta-analysis of serum iron levels revealed a significantly lower serum iron level in the children with ADHD than in those without ADHD . This provides further evidence of a shortage of body iron stores in children diagnosed with ADHD. Taken together, our findings provide tentative evidence that deficient iron storage in children with ADHD may be involved in the pathophysiology of the condition. However, future longitudinal research is required to confirm/refute this tentative hypothesis.Our results are in general agreement with three previous meta-analyses16 Table . Howeverst Table , we foun45. In brief, iron aids in dopamine synthesis by acting as a co-factor for tyrosine hydroxylase, which is a rate-limiting enzyme for the conversion of hydroxylation of tyrosine to L-DOPA, a precursor of dopamine46. Iron deficiency may therefore result in disruption of dopamine activity, as shown in several animal studies48. This dysregulation of dopaminergic neurons may further result in multiple frontal dysfunctions that mimic the symptoms of ADHD49. In addition, ADHD has been found to be more prevalent in patients with restless leg syndrome (RLS) (27.62% with a diagnosis of ADHD), and iron deficiency and dopamine system dysregulation has also been reported to play an important role in RLS50. Therefore, iron deficiency with resulting brain dopamine dysfunction may be a common pathway for the pathophysiology of both disorders. In addition to the dopamine theory, lower ferritin levels may provide indirect evidence of elevated oxidative stress17, and heightened oxidative stress has also been reported in patients with ADHD51. This increased oxidative stress burden may disturb neurodevelopmental trajectories and gene functions potentially predisposing to the onset of ADHD51. However, given the observational nature of our data, the precise mechanisms and directionality of any relationships we observed cannot be verified.The relationship between ID and ADHD may be explained by several possible pathophysiological mechanisms. First, low peripheral iron levels, indicating insufficient iron storage, may dysregulate dopaminergic neurons, which may play a prominent role in the pathoetiology of ADHD28. However, another MRI study by Adisetiyo et al. failed to find an association between brain iron levels and serum ferritin levels42. Therefore, further studies are required to explore the relationship between brain and serum iron levels.Our meta-analysis focused on peripheral iron levels rather than brain iron levels. The extent to which peripheral and brain iron levels are correlated remains unclear. Cortese and colleagues provided some evidence that brain iron levels in the bilateral thalamus were significantly lower in children with ADHD compared to healthy controls52. However, only four of the nineteen datasets recruited drug-free participants, and most of the other studies did not provide much information about the medications prescribed to their participants. Therefore, further studies are warranted including drug-free participants only to further investigate the relationship between methylphenidate and ferritin level in children with ADHD. In addition to the potentially confounding effect by medication, the different food intake pattern would also contribute impact on the iron storage. For example, Lane and the colleague (2014) provided evidences about the enhancing effect on iron absorption by vitamin C intake43. Studies recruited subjects with high vitamin C intake or iron supplementation would have confounded results compared to others27.In the main result of our meta-analysis, high heterogeneity had been detected through the results. To address the potential source of heterogeneity, we arranged subgroup meta-analysis and meta-regression to investigate it. In part of subgroup analysis, if we only included the studies that recruited children who did not take medications, the difference in ferritin level between the ADHD and control groups became non-significant. Although, no obvious interactions have been reported between most drugs and ferritin level, D’Amato suggested that methylphenidate may cause a poor appetite and possibly less iron intake in children with ADHD53. Therefore, further studies investigating ferritin level and ADHD symptoms may need to take this factor into account, before analyzing their study results. On the other hand, our meta-regression did not show significant associations between the prevalence of ADHD in children with ID and mean age, mean proportion of females, and geographic latitude of where the study was conducted.Finally, in part of meta-regression, we tried to address the potential impact of some clinical variables on the peripheral iron levels. The differences in serum ferritin levels between the children with ADHD and the controls were only significantly moderated by mean age but not by other factors including proportion of females, subtype of ADHD, cognition (in forms of mean IQ), sample size of the ADHD group, and geographical latitude of where the study was conducted. We are uncertain about the significance of the finding that the difference in ferritin level in ADHD and control groups became larger with age because there were no previous reports or studies addressed this issue. However, previous studies showed that the reference range of ferritin level became wider and higher with age in pediatric population42. Third, we could not fully exclude the potential confounding effect of food iron intake on peripheral iron status because only a few studies provided such information27. In addition, we could not completely rule out the potential confounding effect of the ability of different types of assay to detect iron due to the inconsistent reporting of those data across the included studies. Fourth, we lacked comparisons of changes in iron status in the children with ADHD in long-term follow-up because there were few cohort studies39. Fifth, we could not perform subgroup meta-analysis of plasma ferritin, iron, or transferrin due to the limited number of datasets available in the studies. Finally, we could not perform meta-regression of peripheral iron levels and attention because of the limited data available.There are several limitations to the current study. First, the total number of included studies was relatively small, and therefore there was a risk of type I and type II errors. Second, our main targets focused on peripheral samples of iron status parameters rather than CNS parameters because few studies provided such informationThe results of our meta-analysis suggest that children diagnosed with ADHD have lower serum ferritin levels compared to those without ADHD. We also observed that the children with ID were more likely to have ADHD and to suffer from more severe ADHD symptoms compared to those without ID. We therefore suggest that further studies are warranted to explore the benefits of iron supplementation in children with ADHD with ID, in particular those with more severe ADHD symptoms. However, given the cross-sectional nature of most of the available studies, further longitudinal and cohort studies are required to thoroughly evaluate the relationships between iron status and ADHD symptoms, and to elucidate the potential pathophysiological mechanisms. In addition, further studies may be needed to investigate the relationship between methylphenidate and ferritin level to exclude any potential effects of methylphenidate on oral iron intake.54  guidelinesThe inclusion criteria were: (a) observational studies, including a cohort or cross-sectional study design, comparing all peripheral iron status parameters including iron, ferritin, and transferrin levels in children with ADHD (confirmed by either a structured or non-structured diagnostic interview) and controls; and (b) clinical human studies. We excluded preclinical studies, review articles, meeting abstracts, or peer-reviewed original articles not conducted in humans.th, 2017 across PubMed, ScienceDirect, Cochrane CENTRAL, and ClinicalTrials.gov databases. We used the following keywords: “(iron OR ferritin OR ferrous) AND (Attention deficit hyperactivity disorder OR ADHD)”. To expand our eligible list, we consulted the reference lists of the included articles and recent reviews56.Two independent authors conducted an electronic systematic literature search from inception to August 9At the eligibility stage, two authors (YS Cheng and PT Tseng) screened the titles and abstracts of all results to assess potential eligibility. The authors then reviewed the full-text articles which were deemed potentially eligible. A final list of included studies was determined and any inconsistencies were resolved by consensus or via thorough discussion with a third reviewer (PY Lin).We set the primary outcomes as the difference in peripheral iron levels  between children with ADHD and controls, and the OR of ADHD or severity of ADHD symptoms between children with or without ID. If the data of interest were not available in the articles, we contacted the authors twice over a month to request the data.Two independent authors (YS Cheng and PT Tseng) extracted data using a predetermined list of variables of interest, which included: prevalence/incidence rates of ADHD, prevalence rates of iron deficiency, peripheral iron levels, amount of food iron intake, mean age, gender distribution in the form of the percentage of females, body mass index, percentage of ADHD subtypes, cognitive performance in the form of IQ, parental tobacco smoking/alcohol consumption, ethnicity , parental history of ADHD, geographical latitude of where the study was conducted, and the type of assay used to detect the iron level.41. For cohort studies, the Newcastle-Ottawa Scale score ranges from zero to nine, with a score of six or more being classified as a high-quality study40.We used the Newcastle-Ottawa Scale for cohort studies and case control studies. For cross-sectional studies, we used a modified version of the Newcastle-Ottawa Scale for observational studies to assess the quality of the included studies. This modified version of the Newcastle-Ottawa Scale score for observational studies ranges from zero to six, and a score greater than three was classified as a high-quality study. For case control studies, the Newcastle-Ottawa Scale score ranges from zero to ten, with a score greater than five being classified as a high-quality studyThe current study was conducted in two parts. First, we analyzed the data considering iron in relation to the children with ADHD compared to the controls. Second, we analyzed the data about the severity of ADHD symptoms or OR of ADHD in the children with ID compared to the controls. To control for the potential confounding effects of clinical variables, we performed further meta-analysis based on the pooled adjusted OR from the recruited studies. In brief, we extracted the adjusted OR with regards to the association of ADHD in the children with ID from the recruited studies to calculate the pooled adjusted OR of the association between ADHD and ID.57. In brief, random-effects modeling is more stringent than fixed-effects modeling and incorporates a between-study variance in the calculations58. For continuous outcomes (i.e. differences in iron levels between the children with ADHD and the controls), we calculated Hedges’ g and 95% CI. For dichotomous outcomes  we calculated the OR and 95% CI.Based on the presumed heterogeneity of background and population among the recruited studies, we conducted the meta-analyses with a random effects model rather than a fixed effects model59. The I2 statistic should be interpreted as the proportion of heterogeneity a study estimates that is due to heterogeneity60. For publication bias, we used direct inspection of funnel plots for fewer than 10 datasets61 and Egger’s regression test for 10 or more datasets62. We also used the Duval and Tweedie’s trim-and-fill procedure to adjust the ESs when publication bias was evident63. We also used a sensitivity test with one study removed to investigate any potential outliers present in the recruited studies64.Heterogeneity was assessed using the Cochran Q test65. The main clinical target for subgrouping included sample sources, subjects who were or were not drug free, and the situation when blood was drawn. When data were available for a moderator in more than five studies, we performed unrestricted maximum likelihood random-effects meta-regression to explore any potential source of heterogeneity. The moderators of interest included mean age, female proportion, body mass index, percentage of ADHD subtypes, mean IQ, percentage of parental tobacco smoking/alcohol consumption, percentage of each ethnicity, percentage of parental history of ADHD, sample size of the disease groups, and geographical latitude of where the study was conducted.To discover any potential sources of heterogeneity, subgroup analyses were performed to explore potential interactions between clinical variables and peripheral iron status parameters in the children with ADHD compared to the controls. We only performed subgroup analysis whenever data from three independent datasets were availableThe meta-analyses were conducted using Comprehensive Meta-Analysis software, version 3 .The datasets generated and analyzed during the current study are available from the corresponding author on reasonable request.Supplementary information


OXTR) have been shown to explain some variability in social abilities in control populations. Whether these variants similarly contribute to the severity of social deficits experienced by children with neurodevelopmental disorders is unclear. Social abilities were assessed in a group of children with autism spectrum disorder  or attention deficit hyperactivity disorder  using two established social measures. Scores were compared by OXTR genotype . Unexpectedly, the two most frequently studied OXTR SNPs in the general population (rs53576 and rs2254298) were associated with an increased severity of social deficits in ASD (p < 0.0001 and p = 0.0005), yet fewer social deficits in ADHD (p = 0.007 and p < 0.0001). We conclude that these genetic modifier alleles are not inherently risk-conferring with respect to their impact on social abilities; molecular investigations are greatly needed.Oxytocin is a pituitary neuropeptide that affects social behaviour. Single nucleotide polymorphisms (SNPs) in the oxytocin receptor gene ( Genome wide association studies (GWAS) and candidate gene studies now seek to identify specific underlying genes and polymorphisms that influence social abilities1. Oxytocin and vasopressin are pituitary neuropeptides that exert robust effects on social processes in animal models4. In humans, it is hypothesized that these peptides may influence social behaviour by enhancing the saliency of social cues, or by attenuating fear/stress5. Plasma oxytocin levels  have been shown to correlate with facial emotion recognition abilities8. In control populations, common polymorphisms in oxytocin or vasopressin receptor genes (OXTR and AVPR1a) have been associated with differences in empathy11, prosocial temperament12, social sensitivity17, and stress reactivity in social contexts19. The area on chromosome 3 carrying the OXTR gene (3p24–26) has emerged on GWAS with respect to risk for autism spectrum disorder (ASD) at a genome wide significance level20. Meta-analyses indicate that certain neuropeptide variants are more common in individuals with ASD than in controls21, and may influence social abilities in the general population22.The past decade has yielded major advances in our understanding of the genetics of human social behaviour. Twin and family studies have shown that traits such as empathy and social cognition have moderate to high heritability24. Both disorders are associated with social deficits, inattention, and hyperactivity to varying degrees25, leading some to propose that they may be different manifestations of an overarching disorder23. In addition to rare genetic mutations and environmental factors, the additive effects of common genetic variants are hypothesized to contribute to the development of these disorders26, and may explain some of the observed heterogeneity in behaviour, abilities, and psychopathology. Preliminary investigations suggest that single nucleotide polymorphisms (SNPs) in OXTR may act as modifier alleles with respect to the severity of social deficits experienced by individuals with ASD  general risk factors for social impairment across populations (i.e. effects span diagnostic boundaries), or 2) specific modifier alleles in certain behavioural or biological context (i.e. disorder specific effects). Two recent studies have shown that OXTR variants were associated with a similar magnitude and direction of social differences in children with ASD and their unaffected relatives29. This question, however, has not yet been examined across different diagnostic groups, where the environmental, behavioural, and genetic architecture differ. Given the increasing number of studies employing trans-diagnostic approaches in psychiatry30, it is important to examine whether behavioural risk variants function similarly across disorders.ASD and attention deficit hyperactivity disorder (ADHD) are common childhood onset neurodevelopmental disorders that are highly heterogeneous, present along a spectrum of severity, and often comorbidOXTR and social abilities in a large sample of children and youth with ASD or ADHD and present the first cross disorder comparison of genotype effects. To extend on preliminary research to date, we used two validated continuous social metrics, and restricted initial hypotheses to Caucasian participants only, given evidence of possible ancestral differences in the effects of OXTR on social abilities32. First, in our group of children with ASD, we confirmed several associations between social deficits and OXTR variants  that had been previously shown in smaller samples. New associations were detected in the group of children with ADHD. Second, we compared the magnitude and direction of the impact of common variation in OXTR on social abilities between diagnostic groups (ASD vs. ADHD). Based on the family studies described above, and the high degree of symptom overlap and comorbidity between ASD and ADHD, we hypothesized that genotype effects would not differ by diagnosis. However, unexpectedly, highly significant diagnostic differences were detected, with effectively a reciprocal direction of association between genotype and social abilities between the two diagnostic groups. Our findings indicate that common polymorphisms in neuropeptide receptor genes likely represent a specific and not a general risk modifier, with effects that vary by diagnosis in the context of different biological, behavioural, or environmental conditions. These results have implications for all analyses involving common alleles and complex traits.In this study, we examined the association between four SNPs in 33. OXTR allele frequencies did not deviate from Hardy Weinberg equilibrium (Supplementary Table The sample consisted of 617 participants with either ASD or ADHD (n = 404 Caucasian). The ASD group had lower mean intelligence quotients (IQs), and higher anxiety levels  (see methods)35. Therefore, throughout the manuscript, higher scores on either metric suggest greater social deficits. Correlations between measures in ASD and ADHD are shown in Supplementary Tables Severity of social deficits were quantified by examining the number of incorrect items selected by the participants on the Reading the Mind in the Eyes Test (RMET)OXTR SNPs with prior evidence of genotype effects on social abilities within each diagnostic group , restricting the sample to those of Caucasian ancestry only, and adjusting for other possible confounding factors (see Methods). When considering multiple testing, five comparisons (3 in ASD and 2 in ADHD) across two social metrics yielded a corrected p-value of 0.005 as the threshold for significance for an overall alpha of 0.05.Using logistic regression, we initially examined OXTR rs53576 G-allele carriers, rs2254298 A-allele carriers, and the rs237887 AA carriers would have greater social deficits, based on previous literature. In line with our hypotheses, rs53576 G-allele carriers (GG/GA) had higher SCQ scores . Differences were non-significant on the RMET for this SNP   also had higher SCQ scores in the ASD cohort , suggesting greater social deficits  and the RMET , although neither finding would survive correction for multiple comparisons  and RMET ; the direction of deficits was congruent between metrics , yet opposite to the direction hypothesized, and detected in the ASD group.In the Caucasian ADHD cohort, we hypothesized that OXTR SNPs and social abilities were confirmed in the group of children with ASD, but not ADHD.The results from our primary hypotheses are displayed in Fig. OXTR rs2254298 and rs237887 in ADHD, as well rs13316193 in ASD) , a p-value of 0.006 was used for significance regarding the interaction term. In this context, we also tested for genotypic differences in social abilities across all SNPs in the remaining diagnostic groups , indicating that the ‘risk variant’ in ASD showed a significantly different effect in ADHD . In ADHD, the AA/GA-allele was associated with fewer social deficits on the SCQ , opposite to the direction initially detected in the ASD group (OR = 1.2 in ASD). The diagnostic interaction term for OXTR rs2254298 was not significant on the RMET , where the risk allele had no significant effect in ADHD or ASD . In summary, across multiple OXTR variants, there was evidence that the hypothesized risk allele was associated with more significant social deficits in ASD, but fewer social deficits in ADHD.For rs53576, the diagnostic interaction terms were significant on both the SCQ and the RMET  RS3 microsatellite length, and (2) the impact of ancestry on OXTR findings. Greater length of the AVPR1a RS3 microsatellite was previously associated with greater receptor expression levels and superior social abilities in typically developing populations38, although no effect was detected in a large sample of children with ASD29. Previous studies have also found evidence for a differential direction of effects of OXTR polymorphisms in Caucasian vs. non-Caucasian individuals, particularly for rs225429832.As secondary aims, we also examined (1) whether social abilities varied by arginine vasopressin receptor 1a AVPR1a is the gene coding for the corresponding vasopressin receptor. Upstream of the exon is a microsatellite promoter region, which includes an RS3 segment of CT, TT, and GT repeats. The RS3 segment varies in length; in our sample the range was 310–346 base pairs (bp), with a median of 328. We categorized each individual’s promoter length as ‘long’ or ‘short, with the cut-point placed at 328 bp, as this was both the median in our sample, and similar to cut-points used in previous studies . We considered those carrying two ‘short’ alleles to be the high-risk group, and compared them to those with two ‘long’ alleles as the low-risk group. In the group of Caucasian participants with ASD, there were no differences in social abilities based on microsatellite length on the SCQ , or the RMET . Similarly, in the ADHD group, there were no differences in social abilities by microsatellite length on the SCQ  or on the RMET .OXTR SNPS, on the SCQ and on the RMET . In the ADHD group, there were no significant ancestry*genotype interactions on the RMET , but significant effects were observed on the SCQ for rs2254298 , where the opposite direction of an association between the risk allele and social deficits was detected in the non-Caucasian cohort  compared to the Caucasian cohort [OR = 0.7 (95% CI: 0.6–0.8) p < 0.001]. Interaction terms were also significant in ADHD for rs53576  and rs13316193  on the SCQ.We subsequently combined data across Caucasian and non-Caucasian participants, and tested for ancestry*genotype interactions. The aim was to determine whether the direction of genotype effects was sufficiently similar between the Caucasian and non-Caucasian groups to justify performing the genotype group comparisons on the entire combined sample, irrespective of ancestry. For the ASD cohort, ancestry*genotype interaction terms were non-significant for all For SNPs where the ancestry*genotype interactions were conservatively non-significant (p > 0.05), we pooled data across ancestry groups, and calculated the combined odds ratios in the larger sample , as opposed to categorical (GG/GA vs. AA). Results were similar with either model 43, we post-hoc hypothesized that differential anxiety levels between the two clinical groups could potentially explain the reciprocal pattern. Anxiety was quantified through parent report on the Child Behavior Checklist anxiety subscale (CBCL-anxiety) and the Revised Children’s Anxiety and Depression Scale (RCADS). We compared anxiety scores by diagnosis, then by genotype, and subsequently included anxiety as an additional covariate in the original SNP-SCQ models. Anxiety analyses were restricted to participants who also had SCQ scores available and were of Caucasian ancestry , to facilitate comparison to previous findings.Next, given an emerging hypothesis that oxytocin may affect social behaviour by decreasing anxiety or fear responses, potentially at the level of the amygdalaOn the CBCL-anxiety, the ASD group had higher mean T-scores Table  and highFor genotype group comparisons, we tested for effects of rs53576 and rs2254298 on anxiety measures in ASD and ADHD separately. No genotype effects were detected on the RCADS for either SNP (p > 0.05). For rs53576, a modest genotype effect was detected on the CBCL-anxiety raw score in the ASD group in line with the direction of effects seen with the SCQ . There were no significant effects of rs53576 on CBCL-anxiety in the ADHD group . The SNP*diagnosis interaction term was non-signification (p = 0.09), suggesting a lack of differential effects of genotype on anxiety between the two diagnostic groups. For rs2254298, CBCL-anxiety scores were modestly affected by genotype in the ADHD group only . The diagnostic interaction term was again non-significant (p = 0.3).OXTR on SCQ scores were otherwise unchanged . Overall, data suggest that OXTR genotype may affect anxiety to some extent, but a reciprocal pattern between diagnostic groups as seen on social measures was not observed, and anxiety did not explain the differential effects of genotype on social outcomes by diagnosis.We subsequently included CBCL-anxiety score as an additional covariate in the SCQ models for rs53576 and rs2254298. Although CBCL-anxiety was significantly associated with SCQ in the overall model, results regarding the effects of OXTR SNPs and social abilities seen in smaller ADHD cohorts, although several new associations were detected in this larger sample, and 3) significant diagnostic differences in the association between OXTR genotype and social abilities .In this study, we examined how common polymorphisms in neuropeptide receptor genes affected social abilities in a large group of children and youth with ASD or ADHD. This is the first study comparing genotype effects across two neurodevelopmental disorders, with the largest ADHD cohort, and one of the largest ASD cohorts for this type of analysis to date. Other strengths of this study include: participants from two clinical groups who were recruited and characterized using the same research protocol; detailed phenotyping on both participant and caregiver completed metrics; and examination for potential ancestral differences in genotype effects. Our main findings were: 1) confirmation of several previous associations regarding neuropeptide receptor genotype and social abilities in our large group of children with ASD, 2) a lack of replication of previous associations between et al. examined genotypic differences in social abilities in a group of 79 children with ASD, 53 unaffected siblings, and 62 controls, of varied ethnicities6. They found that carriers of the A-allele of OXTR rs2254298 had higher levels of social impairment, and carriers of the G-allele of OXTR rs53576 performed worse on an affect recognition task6. Skuse et al. tested for associations between 60 OXTR SNPs and 31 AVPR1a SNPs and social abilities in an ASD cohort of 198 families from the United Kingdom and Finland, of mostly Caucasian ancestry29. Only OXTR rs237887 genotype affected face recognition memory, where AA carriers performed significantly worse. Length of AVPR1a RS3 microsatellite promoter region did not impact social abilities in their sample29, nor in ours. A recent meta-analysis found both the OXTR rs237887 A-allele and the rs2254298 A-allele were also risk-conferring with respect to an ASD diagnosis21. It would follow that in certain vulnerable families, specific OXTR common variants may push a small subset of those at risk over the diagnostic threshold.Our findings are in line with direction of effects described in previous ASD cohorts and family studies. For example, Parker OXTR on social functioning in ADHD28. Park et al. found that rs53576 AA allele carriers had fewer social deficits in their sample of 119 participants. However, in our ADHD sample, OXTR rs53576 GG allele carriers and rs2254298 A allele carriers had fewer social deficits, opposite to the direction of effects seen in our ASD group. For OXTR rs53576, this finding may be more in keeping with patterns observed in control populations. In a recent meta-analysis of mostly typically developing adults, rs53576 G-allele homozygotes had better social abilities on a variety of metrics22. Similarly, a previous study using the RMET found that healthy adolescents who had the OXTR rs53576 GG genotype had higher accuracy overall18. Our data suggest that the direction of impact of common variants in these receptors vary by disorder- a protective variant in one condition may increase risk in another. Overall, this would indicate that common polymorphisms in OXTR represent a specific vulnerability factor, and not a universal risk factor with respect to social functioning.Few studies have examined the impact of 44, that affect the structure or function of OXTR. Alternatively, they may be markers of functional differences in the non-coding regulatory elements of neuropeptide receptor genes, indirectly affecting receptor expression levels. SNPs in non-coding regulatory elements were recently shown to exert a robust effect on oxytocin receptor expression levels within specific brain regions in prairie voles45. Similar investigations in humans are lacking and are greatly needed. At the same time, large and rare genetic variants may be more common in ASD, and could be potentially associated with more significant disruptions on oxytocin signaling47. For example, contactin-associated protein 2 (CNTNAP2) mutations have been associated with ASD and developmental delay46. A recent mouse model of ASD using CNTNAP2 knockout showed disrupted oxytocin expression and social deficits, which were corrected with exogenous oxytocin administration47. While usually we conceptualize rare variants as acting on a background of common variants, the implication of our study is genetic background may also play a critical role in modifying the impact of common ‘risk’ variants on behavioural phenotypes.Mechanistically, it may be that these non-coding intronic SNPs co-localize with specific receptor haplotypes, other important exons, or certain rare variantsHow exactly similar changes in receptor expression or function could result in disparate behavioural consequences in different diagnostic groups is unknown. Possible explanations include: 1) specific neurocircuits contributing to social deficits may vary between the disorders, 2) other diagnostic differences in environmental, hormonal, or epigenetic processes may be differentially accentuated through oxytocin signaling or 3) measurement factors or confounding.48, and that oxytocin may potentially enhance transmission in these circuits through its effects on interneurons49. It may be that the brain circuits, regions, or underlying behavioural constructs contributing to differences in SCQ scores may vary between diagnostic groups. While our exploratory analyses involving anxiety measures suggested that OXTR genotype may also impact on anxiety levels to some extent, a reduction in anxiety alone was insufficient to explain the differential OXTR effects across diagnostic groups.With respect to neurocircuitry, emerging literature indicates that social and fear perception involve complex networks centred on the amygdala and reward centresOXTR rs53576 G-allele was associated with increased environmental sensitivity, which led to more adverse outcomes under conditions of early childhood adversity or exclusion17. G-allele carriers were also shown to experience a more beneficial response to receiving positive social support as indicated by salivary cortisol levels50, and were more likely to seek social support under stress51. In this context, perhaps children with ASD are less likely to experience the stress buffering effects of social contact given their underlying social deficits, putting the more ‘sensitive’ allele group at greater risk. At the same time, there is evidence to suggest that oxytocin may play a role in suppressing the cortisol stress response52. Given evidence of divergent cortisol patterns in ASD vs. ADHD , it would follow that an OXTR variant leading to increased cortisol activity would be disadvantageous in ASD, but potentially advantageous in ADHD. Differential epigenetic regulation of OXTR gene expression between the two disorders could also potentially explain diagnostic differences in SNP effects . While common confounding factors were adjusted for in our analyses, the role of clinical severity, adaptive functioning, and parental stress or psychopathology were not explored, and could potentially affect response patterns on either social metric. The impact of different traits and measurement factors on SCQ scores in ASD and ADHD in particular merits further exploration.In terms of other limitations, despite our sample size, we may have been underpowered to detect more subtle differences, including interactions with ancestry or analyses on the smaller group with RMET and IQ scores. Lack of statistical significance would therefore not necessarily rule out a possible biological effect of genotype on social behaviour for these measures. Analyses including a comorbid ASD/ADHD group, a control group, or a group of unaffected family members, would have proven interesting comparisons but were not feasible with the existing dataset. While results were statistically significant, differences between genotype groups were generally small and not meant to imply clinical utility. Human molecular/ expression data is greatly needed to clarify the mechanisms through which these variants may influence receptor function and downstream behaviours.OXTR genotype effects across these disorders ought to examine the role of the hypothalamic pituitary axis social neurocircuitry, environmental social stress, and rare genetic, or epigenetic differences as possible mechanisms. Molecular studies investigating the functional impacts of these SNPs in humans are also greatly needed.In summary, our findings indicate that common polymorphisms in neuropeptide receptor genes act as specific  modifier alleles regarding social phenotypes in children with neurodevelopmental disorders, with effects that vary by diagnosis. Our findings therefore contribute to the often-conflicting literature regarding these SNPs. We are the first to implicate potential diagnostic differences as one explanation for heterogeneity in findings. Future studies comparing 25. All participants (n = 614) were between 4 and 21 years of age, and had a clinical diagnosis of ASD or ADHD  Network, a coordinated multi-centre research initiative examining the neurobiology of neurodevelopmental disorders. Hospital Research Ethics Boards approved the study protocol at each participating institution ; all experiments were performed in accordance with relevant guidelines and regulations. Informed consent was obtained from parents of all participants; further details of the protocol are described elsewherents n = 64 were be61, developed based on the items and factors in the Autism Diagnostic Interview-Revised62. Higher SCQ scores (out of 39) indicate a greater risk, with a cut-off of > 15 proposed to distinguish between those with and without ASD35. For context, typically developing children usually score under 10 on the SCQ, while those with ASD have mean scores closer to 20 and above64. Previous research suggests that mean scores on the SCQ are comparable in children with ASD across IQ strata, and it is valid for use in children with a mental age above 2.061. For this analysis, we examined the total prorated scores on the 28 social interaction and communication items only, excluding the items pertaining to restricted/ repetitive behaviours. We did not adjust for IQ for this measure . The Reading the Mind in the Eyes Test (RMET) is a standardized test of social perception abilities65. Higher scores on the RMET are indicative of more accurate social perception. The child version of the RMET was used in this study, containing a total of 28 items34. Typically developing children tend to score between 15–20 out of 28 on this measure, while children with ASD tend to score 2–4 points lower than control subjects34. RMET scores are known to vary with IQ25, therefore IQ was included as a covariate for these analyses. To more easily facilitate comparison of genotype effects across both measures, we report RMET scores with respect to the number of incorrect items. Therefore, throughout the manuscript, higher scores on either metric suggest greater social deficits. Other behavioural traits were quantified using the Child Behavior Checklist (CBCL) subscales68, and the Revised Children Anxiety and Depression Scale (RCADS)69.The Social Communication Questionnaire (SCQ) is a validated measure completed by a parent/caregiver to screen for ASDOXTR from the third intronic region  were selected for genotyping based on existing literature at the time of study design suggesting an association between these markers and social abilities in participants with ASD or ADHD  was completed using Ldlink33, and the 1000 Genomes Project database of Caucasian samples  assembly and to elevate the Tm but otherwise maintain the amplified position73. Results were analyzed using the software GeneMapper v. 3.7 (Life Technologies).SNPs were analyzed on the MassARRAY Analyzer 4 system using iPLEX Gold chemistry  using the primers in Supplementary Table 25. Logistic regression was chosen for the main analyses given that scores on both metrics are sums of binary variables and therefore, follow a binomial distribution. Initial hypotheses were examined in the ASD group  and ADHD group , including Caucasian participants only. We selected one specific categorical genotype risk pattern per SNP  for statistical testing based on the positive findings described in previous papers . We used a logistic regression analysis to examine the proportion of items selected as ‘yes’  or incorrect (for the 28 RMET items), using the PROC LOGISTIC function in SAS, which allows us to specify both the total score and the number of trials that this score is based on in the model outcome. This approach permitted adjustments for total number of items . We adjusted for the contribution of the following predictor variables: genotype group, age, sex, ancestry rs Table . We subshttp://www.braininstitute.ca/braincode/.The datasets generated and analyzed during the current study are publicly available through Brain-CODE. Supplementary Information


Prosocial skills were measured with the Interpersonal Reactivity Index. The ADHD group had a larger discrepancy between ultimatum game and dictator game offers than controls, indicating strategic rather than fairness driven decisions. This finding was supported by self-reports showing fewer individuals with ADHD than controls who considered fairness as motive for the decisions. Perspective taking or empathic concern did not differ between groups and was not significantly associated with offers. In conclusion, the results suggest that rather than a failure to understand the perspective of others, children and adolescents with ADHD were less motivated by fairness than controls in simple social situations. Results encourage the use of economic games in ADHD research.This study examined reward-related decision-making in children and adolescents with ADHD in a social context, using economic games. We furthermore examined the role of individual differences in reward-related decision-making, specifically, the roles of reward sensitivity and prosocial skills. Children and adolescents (9–17 years) with ADHD-combined subtype ( Attention-deficit/hyperactivity disorder (ADHD) is a common childhood-onset disorder characterized by age-inappropriate levels of inattention and/or hyperactivity–impulsivity that are present in multiple settings , 4. In ainteractions between cognitive control and motivational states, e.g., , ,  and rewas, e.g., , 61. This, e.g., , 43, 68.Research on reward-related decision-making in individuals with ADHD has mainly focused on risk tasks (gambling) and temporal discounting tasks . Children and adolescents with ADHD show increased risky performance and a stronger preference for small immediate rewards compared with controls , 32.social interactions in individuals with ADHD. Indeed, children with ADHD demonstrate fewer prosocial behaviors such as empathy , assesses ultimatum bargaining [Paradigms assessing rgaining . An ultirgaining . This dergaining , 25. In rgaining .In addition to these strategic considerations, another possible motive for proposing equal splits in the UG is fairness , 55, 67.These games have been thoroughly studied in children and adolescents without ADHD, for review see . In 3- tIn summary, the primary goal of this study was to assess reward-related decision-making in social contexts in children and adolescents with ADHD and controls. Specifically, considerations of fairness versus strategic bargaining were assessed by administering the UG and DG in the role of the Proposer. Self-reports provided more insight into the motives behind decisions. Because ADHD is associated with atypical reward sensitivity and lower cognitive control , 38, then = 29) were recruited through Karakter, Child and Adolescent Psychiatry Department of the Radboud University Nijmegen Medical Centre. Control subjects (n = 38) were recruited through local advertisements and schools. The groups did not significantly differ on gender, age, and IQ  were included. Additional questionnaires were used as descriptive (not diagnostic) instruments (Table n = 20) discontinued their medication 24 h prior to testing [Clinical assessment: All ADHD subjects were previously diagnosed with ADHD-C by accredited clinical psychologists/psychiatrists. Furthermore, the diagnosis of ADHD-C was re-confirmed by a trained psychologist at the time of the study using a structured parent interview: the Diagnostic Interview Schedule for Children (DISC–IV) . Particits Table . ParticiControls were excluded if they met criteria for psychiatric disorders on the DISC-IV, as assessed by a trained psychologist, or scored within clinical range on the Disruptive Behavior Disorder Rating Scale . They were told that the Responder was another participant in the study of the same age who could either accept or reject their offer. If the offer was accepted, the money would be divided as proposed. If the offer was rejected, neither player would receive anything. It was emphasized that the game was played for real money and that they would be paid on their next visit (study procedure) based on the decision made by the Responder. It was further emphasized that all players would remain anonymous and that they would not meet or interact in any of the subsequent experiments. The participants indicated their offer on a paper with two rows indicating amounts displayed in 50-cent increments from €0 to €5. In reality, there was no responder and when offers fell below €2 the experimenters told participants during their next visit that the offer was rejected. If the offer was higher or equal to €2, participants were told that their offer was accepted and they were paid accordingly. Rejecting offers that are much lower than 50 % of the total amount would be a realistic reaction .Participants played a one-shot DG, also in the role of the Proposer. The procedure was the same as outlined above, except that the Responder did not have the option to reject the offer and participants were explicitly informed of this. Furthermore, they were told that they would make this offer to another, anonymous partner. After their choice, they received the amount that they wanted to keep for themselves immediately. They were not informed of this immediate payoff before their choice.After completing both games, all participants were asked to respond to three questions concerning the games: “How did you make your decision during the game?” (for UG and DG) and “How difficult was it to make these decisions?” These were asked as open-ended paper and pencil questions to avoid evoking response biases. The responses were evaluated qualitatively and categorized based on the content (see below).This study was approved by the local medical ethics committee consistent with the Dutch Act on Medical Research Involving Human Subjects. Informed consent was obtained from all participants and their parents. This study consisted of three consecutive test days. This experiment was part of a larger project with other experimental studies reported elsewhere. Participants completed the IQ assessment, UG and DG, and questionnaires in the first session in the behavioral laboratories of the Radboud University. The families received €30 for participating in all the sessions.U tests to examine whether participants with ADHD differed from controls on UG offers, DG offers and strategic bargaining (UG–DG offers). Effect sizes for the Mann–Whitney U (denoted as r) are computed by dividing the Z statistic by the square root of the sample size, with small, medium and large effect sizes of r = .01, 0.3 and 0.5, respectively [α = .0167) as recommended to identify group differences per category following significant Chi-square tests [rho = .01, p = .96) or DG offers . Therefore, it was not included as a factor in the analyses.The dependent variables were not normally distributed. Therefore, we performed non-parametric Mann–Whitney ectively . Signifire tests . Age didα = .0167). Responses on the UG and the DG question could be stratified into the categories: (1) fair or (2) strategic. Responses to question 3 were categorized into two options: (1) difficult or (2) easy. For all three questions, the answer was assigned to a third category if a participant responded not to know their motive. To assess which consideration contributed to the offers in the games, a Kruskal–Wallis test was conducted for the three response categories. If the Kruskal–Wallis test was significant, post hoc Bonferroni-corrected Mann–Whitney U tests were conducted (α = .0167). For these analyses, the coded responses (fair/strategic/do not know) to the self-report questions were entered as independent variables, while offer sizes and the difference (UG–DG offers) were the dependent variables.To examine between-group differences in fairness versus strategic considerations in the UG and DG offers and their difference score, responses were stratified into three categories and compared between diagnostic groups using Bonferroni-corrected Chi-square tests  did not complete the scales and were excluded.To examine whether empathic concern and perspective taking correlated with strategic bargaining, Spearman rho correlations were computed across groups. Bonferroni corrections for multiple comparisons were applied, M = €2.40; SD = 0.26). The mode was €2.50 and the range €1–3. As expected [M = €0.90; SD = 1.05). The mode was €0 and the range €0-2.50.In accordance with previous reports , the meaFor the IRI, the mean score over all participants for perspective taking was 12.67 (SD = 4.18); for empathic concern, it was 13.14 (SD = 3.52). There were no significant group differences in either of the scales  = 1.74, p = .24; Table The ADHD and control groups differed in the DBDRS and CBCL scales Table . The ADHχ2,75 = 1.7U = 537.00, p = .80, r = −.03). In the DG, the ADHD group made lower offers than controls . The Chi-square analysis clarified this finding by showing a group difference in the fair/intermediate/unfair categories  = 8.37, p = .02). This group difference was driven by the lower amount of fair offers from ADHD participants  (n = 1) than controls . There were no group differences in the intermediate category  or in the unfair category .For UG offers, we found no significant difference between the control and ADHD group , indicating that the ADHD group showed more strategic bargaining than controls  = 2.00, range = 0–2.50) had a significantly larger difference between the UG and DG offer than the control group : Children with ADHD made lower offers on the DG compared with controls  and there was no significant group difference in the UG . Furthermore, there were no significant correlations between ODD/CD symptoms on either the DBDRS or CBCL and offers made on both games . There were also no significant correlations between offers on either game and the CBCL scales social problems, rule-breaking behavior or aggressive behavior . This suggests that our effects were not driven by the individuals with comorbid ODD or CD symptoms.Importantly, the effects remained the same when excluding individuals with comorbid ODD  = .48, p = .62). The UG offer did not significantly differ per response category  = 3.06, p = .11). The mean ranks were 36.65 for fairness and 30.93 for strategy. No participants responded with “do not know”.For Question 1 (decision UG), the ADHD and control group did not significantly differ in the number of participants per response category  = 9.73, p = .006): fewer participants with ADHD (20.7 %) than controls (50 %) reported fairness . There was no group difference in strategy considerations  or in the category “do not know” . There was a difference between self-reports and offers  = 41.75, p < .001): participants who answered with fairness made higher DG offers than those who reported strategy , but not those who responded with “do not know” . Those who considered strategy did not differ from those who responded with “do not know” . Mean ranks were 51.68 fairness, 21.78 strategy and 39.63 “do not know”.For Question 2 (decision DG), the overall Chi-square test was significant  = .25, p = .30). Kruskal–Wallis tests showed that offers in the UG, DG and the difference between UG and DG offers were unrelated to self-reported difficulty  = 1.16, p = .49), DG  = .11, p = .95), difference  = .08, p = .97). The UG mean ranks were 35.27 for fairness, 32.43 for strategy and 28.67 for “do not know”. The DG mean ranks were 33.44 for fairness, 34.96 for strategy and 34.33 for “do not know”.For Question 3 (difficulty deciding), the ADHD and control group did not differ  or empathic concern  with DG offers.There were no correlations between perspective taking  DG offers. This finding may be understood with the model by Myrseth and Fishbach [The current study found that the strategy in the ADHD group was driven by the lower number of individuals making fair DG offers (50 %), but Fishbach . AccordiFishbach , 41. AltFishbach , egoistiThe current study did not find convincing age effects, even irrespective of diagnosis. In the DG, this was to be expected, as prior studies have not found clear differences in fairness between children and adolescents of similar age as those included in our study  and younThe current study had a number of strengths and limitations. Strengths included the use of solid task designs, as the UG and DG are well-established paradigms to assess decision-making in a social context. Applying these to ADHD is an innovative approach to experimentally study reward-based decision-making in social contexts. Furthermore, by combining the UG and DG, we were able to disentangle strategic bargaining from fairness motives. Limitations of this study include the lack of inclusion of self-control and reward sensitivity measures. Therefore, future research may expand the scope of the current study. First, although the literature has supported the suggestion that cognitive control is involved in these tasks, future ADHD studies may directly examine the involvement of cognitive control by including tasks such as the Stop Signal Task . AdditioThis study investigated social reward-related decision-making in children and adolescents with ADHD using the single shot dictator game (DG) and ultimatum game (UG) in the role of the Proposer. In the DG, the likelihood of monetary payoff does not require considering the perspective of others, and children and adolescents with ADHD made less fair offers than controls. In the UG, which does require considering the perspective of another, there was no group difference. Both the ADHD and control groups made offers that were likely to result in a monetary payoff. This pattern illustrates that the ADHD group was characterized by increased strategic bargaining. The results suggest that rather than a failure to understand the perspective of others, children and adolescents with ADHD are less motivated by fairness and more by monetary gain than controls in simple social situations.


Quantitative EEG gives valuable information in the clinical evaluation of psychological disorders. The purpose of the present study is to identify the most prominent features of quantitative electroencephalography (QEEG) that affect attention and response control parameters in children with attention deficit hyperactivity disorder.The QEEG features and the Integrated Visual and Auditory-Continuous Performance Test ( IVA-CPT) of 95 attention deficit hyperactivity disorder subjects were preprocessed by Independent Evaluation Criterion for Binary Classification. Then, the importance of selected features in the classification of desired outputs was evaluated using the artificial neural network.Findings uncovered the highest rank of QEEG features in each IVA-CPT parameters related to attention and response control.Using the designed model could help therapists to determine the existence or absence of defects in attention and response control relying on QEEG. A model has been developed to identify the most prominent features of QEEG, and electrophysiological monitoring method, that affect attention and response control parameters in the IVA-CPT test, a software that helps clinicians evaluate attention deficit hyperactivity disorder. The designed model can help therapists to determine the existence or absence of defects in attention and response control. Attention deficit hyperactivity disorder (ADHD) is one of the most common neurobehavioral disorders, diagnosed in 3–7% of school-age children age 5–9 years) 3. ADHD –9 years Recently, IVA-CPT as a computerized test has been designed according to DSM-IV criteria to evaluate two universal scales  in individuals with ADHD ,11–13. IDespite the benefits of IVA-CPT, it is a time-consuming test and may only identify individuals with high risk of attention deficit. On the other hand, the different levels in the individuals’ computer skills, their motivation and mood as well as their ability to understand the structure of the test may unpredictably affect the test results. In addition, this test is a quick evaluation of a short period of time and cannot necessarily represent a general clinical experience of the individuals with ADHD. Also, it sometimes has a placebo effect that temporarily affects the level of arousal of individuals and leads to less accurate results ,19.Studies have shown that IVA-CPT can be integrated with the EEG, which is one of the diagnostic indicators for ADHD and can evaluate clinical status of individuals with ADHD ,20–22. EThe methodology of this study is summarized in In the present study, 95 ADHD subjects with ages 7 through 18 years old participated. Participants visited in two rehabilitation clinics in Tehran and Mashhad from 2013 to 2016. Based on the clinical evaluation by psychologists and psychiatrists, they had met the diagnostic criteria of the DSM-IV , to inclIn this phase, before doing EEG test, ADHD subjects took the following steps: washing hair the night before the test and not using any products like sprays or gels; stop taking any medications before the test according to the physician opinion , and also informing the technician performing the EEG of these medications; avoid eating or drinking caffeine at least 8 h before the EEG test; having enough sleep night before the test and other recommendations that depend on the situation of taking EEG, for example, in the rest or task condition. The EEG of participants was measured by using MITSAR with 19-electrode channels. The reference electrode was linked to ears (A1+A2/2). After removing noise of all channels, the sampling rate for acquiring data was adjusted in 250 Hz. The EEG was taken in a situation in which the subjects were relaxed and with closed eyes. The elastic cap with 19 tin electrodes located according to the international 10–20 system in Fp1, Fp2, F3, F4, F7, F8, Fz, C3, C4, Cz, T3, T4, T5, T6, P3, P4, Pz, O1 and O2 sites . Also TeAfter the QEEG, the IVA-CPT was administered to ADHD subjects. IVA-CPT provides quotient scores into four groups consist of response control, attention, attribute and symptomatic . In our Missing data means there are no data values for the variable ,31. The One of the preprocessing stages is normalization. Normalization is a scaling for the prediction or forecasting purpose. Because many of the machine learning techniques have better performance with normal data, input data (QEEG section) were transformed into the 0 to 1 (0.1) range according to the following equation:Equation 1. NormalizationBecause of the insufficient samples for fitting, the binarization was performed to find the absence or present of defect in IVA-CPT parameters. They were binarized according to the interpretation manual of IVA-CPT . AccordiEquation 2. IVA-CPT parameters binarizationTo overcome class imbalance, the adaptive synthetic sampling approach was applied. The adaptive synthetic sampling approach algorithm is built based on Smote methodology to reduce the bias introduced by the class imbalance. This algorithm shifts classification decision boundary to the minority classes that are difficult to learn .One of the problems that might occur in the analysis of high-dimensional data is, the curse of dimensionality. It refers to the state that the large number of dimensions of features in the samples is not useful in analyzing and results in a tangible drop in the modeling accuracy. In this situation, not only is increasing the number of dimensions not helpful, it is also destructive. In order to avoid the curse of dimensionality, feature selection was performed. Feature selection is an important step in the classification tasks which by reducing the number of features, enables the classifiers to have a better performance and learn a stronger solution ,35. In tIn the above relation, RHO is equal to the average of the absolute values of correlation between candidate feature and previous selected features. The ALPHA represents the controlling element with a default value of 0 (no weight) which sets the weighting factor. The above technique was called and used in MATLAB software as below.The output of this operation is the IDX and Z vectors. IDX is equivalent to the order of important features and Z represents the value of the correlation coefficient of each attribute to the output.The extracted outputs in previous phase were the effective features in the classification of IVA-CPT parameters. The extracted features based on the analysis of the ICA had a high correlation with the output of the classification. In this step, the evaluation of selected features was done by a separate classification technique separately. The artificial neural network (ANN) as a simulated model of the human brain model, can detect nonlinear relationships at the desirable level, so it can be an appropriate option for evaluating selected parameters. Hence, 28 neural network models  based on multilayered perceptron architecture and back-propagation algorithm were designed in order to evaluate the effective QEEG parameters in output classification. Multilayer perceptron as a well-known ANN model is formed of an input, an output and one or more hidden layers. In multilayered perceptron process for determination of weights and biases, input–output data are used . Also, tThe input of each data model was related to the effective features of the QEEG. Also, each model has one or two hidden layers fit to the input value and the network output is equal to the binarized IVA-CPT parameters. These models fall into the process of learning with the Levenberg–Marquardt algorithm. Data samples were randomly assigned into three sections: train (70%), test (15%) and validation (15%), and participated in the training process. The accuracy of the network on the classification of samples in the test section was considered as a criterion for the optimization of the selected characteristics.The first step in our study was to perform feature selection and ranking. The features of the QEEG dataset were optimized using the ICA. Then obtained optimal subset of QEEG factors was used to gain a better classification result for each 28 output. The report of the analysis was a list of the most priority QEEG parameters which had been ranked based on their importance in the classification of each output. Because of the high numbers of ranked QEEG factors, the top ten factors were considered. Despite the lack of concrete and fast treatment for ADHD, fortunately many ADHD symptoms including inattention, hyperactivity, impulsivity and response inhibition can be controlled and improved. By identification of deficits in each of these symptoms, therapists can focus on a special cognitive treatment and improve the rehabilitation of children with ADHD. Recently, QEEG clinically has been used in assessment, diagnosis, evaluation and treatment of psychiatric disorders such as ADHD. The QEEG not only has a strong role in differential diagnosis of ADHD, but also has significant heterogeneity among ADHD-diagnosed children and adolescents ,42.The present study was performed to identify the most effective features of QEEG in the determination of IVA-CPT parameters (attention and response control) in children with ADHD. The study was conducted based on using the Independent Evaluation Criterion for Binary Classification to analyze the QEEG parameters. Also, by applying ANN as an optimum technique to evaluate the QEEG features in output classification, the results of features selection were confirmed.Previous researches showed the children with ADHD compared with normal subjects, due to the reduced cortical activity, have EEG differences in brain electrical activity, particularly the increase in δ-band frequency in the fronto-central region. They also pointed the high accuracy and sensitivity of QEEG in differentiation of ADHD from the normal group ,25,41–56Related to such research, the present study focused on ADHD and highlighted that the EEG patterns are also different among ADHD samples. These variations are due to the wide heterogeneity and heterogeneity of ADHD symptoms and also the severity of them . Our anaEpileptic patterns, increase in the power of the δ- and θ-frequency bands, elevated level of δ/β ratio and reduction in β- and α-frequency bands particularly in posterior regions, are the most consistent findings that have been observed in many studies related to the analysis of EEG in children with ADHD ,41,58–62et al. [et al. uncovered the correlation of δ/α and δ/β ratios and the response time [et al. supports the results of the study of Dongen-Boomsma et al. and also highlighted that δ-β ratio may demonstrate the increase in impulsivity [According to Hillard et al. , change nse time . The stuulsivity . Consistet al. indicated a positive relation between δ- frequency band and inattention scores on the self-report scale of individuals with ADHD. Also, the study of Clarke et al. showed the relation between EEG features and Conners’ Rating Scale. The result of these studies confirmed the correlation of the δ-frequency band in frontal region with inattention and also the correlation of δ-β ratio with hyperactivity–impulsivity [et al. was one of the most relevant studies regarding the relationship between IVA-CPT and EEG. In this study, by correlating between the IVA-CPT and EEG parameters, the EEG power spectrum and the δ-phase γ-phase amplitude measurement data were analyzed [Some studies investigated the correlation between EEG and neuropsychological test. Koehler ulsivity ,66. The analyzed . Similaranalyzed ,67. The Today, it is accepted that EEG provides a potential outlook of the neurophysiology of the brain. EEG studies on children with ADHD are performed to explore the different aspects of brain functions in them . In the This study identify the most prominent features of quantitative electroencephalography that affect attention and response control parameters in the children and adolescents with attention deficit hyperactivity disorder.The feature selection was done by Independent Evaluation Criterion for Binary Classification and then was evaluated by using the artificial neural network.The highest rank of QEEG features in each Integrated Visual and Auditory-Continuous Performance Test parameters were uncovered.The designed model could be used in other domains which the scanning and checking of the attention and response control parameters, is important.


The somatosensory temporal discrimination threshold (STDT) is defined as the shortest interval at which an individual recognizes two stimuli as asynchronous. Some evidence suggests that STDT depends on cortical inhibitory interneurons in the basal ganglia and in primary somatosensory cortex. Several studies have reported that the STDT in patients with dystonia is abnormal. No longitudinal studies have yet investigated whether STDT values in different forms of focal dystonia change during the course of the disease.  We designed a follow-up study on 25 patients with dystonia  who were tested twice: upon enrolment and 8 years later. STDT values from dystonic patients at the baseline were also compared with those from a group of 30 age-matched healthy subjects.  Our findings show that the abnormally high STDT values observed in patients with focal dystonia remained unchanged at the 8-year follow-up assessment whereas disease severity worsened.  Our observation that STDT abnormalities in dystonia remain unmodified during the course of the disease suggests that the altered activity of inhibitory interneurons—either at cortical or at subcortical level—responsible for the increased STDT does not deteriorate as the disease progresses. Dystonia is a movement disorder characterized by sustained or intermittent muscle contractions that cause abnormal, often repetitive, movements and postures , 2. DepeThe somatosensory temporal discrimination threshold (STDT) is the shortest interval at which an individual recognizes a pair of stimuli as separated in time , 10, andSince the STDT is abnormally increased in both affected , 19, 20 In healthy subjects, inhibitory interneurons in primary somatosensory cortex play a role in STDT by sharpening and focusing sensory information in the temporal domain , 22. SevTwenty-five patients with primary focal dystonia   were enrThe STDT was investigated by delivering paired stimuli starting with an interstimulus interval of 0 ms (simultaneous pair), and progressively increasing the interstimulus interval in 10 ms steps, according to the experimental procedures used in the previous studies , 27–29. t-test. We then ran a paired sample t-test to evaluate changes in clinical scores and STDT values obtained upon enrolment and at the 8-year follow-up assessment in patients with dystonia. To evaluate whether STDT values changed to a different extent in patients with blepharospasm and cervical dystonia across the two assessments, we also ran a between-group repeated measures ANOVA with factor GROUP  and TIME (two levels: enrolment and 8-year FU). Spearman's correlation coefficient was used to evaluate any relationships between clinical and neurophysiological variables.We first compared STDT values in dystonic patients upon enrolment with those from a group of age-matched healthy controls using an unpaired sample t-test used to compare STDT values in patients upon enrolment, and healthy subjects showed that STDT values in dystonic patients were higher than those in healthy subjects (p < 0.001) (The unpaired sample < 0.001) .t-test revealed a significant increase in disease severity scores in patients   . Only 1 t-test performed to investigate any changes in STDT values in patients between the baseline evaluation and the 8-year follow-up evaluation showed that STDT values remained unchanged  .The paired sample  = 0.83) . Paired F = 0.04, p = 0.83) nor significant GROUP × TIME interaction   . SpearmaThis is the first longitudinal study based on an 8-year follow-up that has evaluated the STDT values during the course of disease in patients with blepharospasm and cervical dystonia. The novel finding of our study is that the abnormally increased STDT values observed in patients with focal dystonias remained unchanged whereas disease severity worsened at the 8-year follow-up assessment.We took several precautions to ensure that the data we obtained were reliable. The neurophysiologist who tested the patients' STDT was blind to the clinical assessment, and the investigators who performed the clinical assessment were not informed of the purpose of the study. Since botulinum toxin leaves STDT values unchanged in dystonic patients , but is A recent study on the effect of aging on STDT measurements showed that STDT values increases with aging . When thOwing to the psychophysical nature of STDT testing, an altered STDT in dystonia may be caused by behavioural/attentional dysfunctions or psychiatric conditions, both of which are known to occur in patients with dystonia , 31–33. Previous studies on healthy subjects have demonstrated that STDT values are modulated by plasticity mechanisms in S1 induced by repetitive transcranial magnetic stimulation at the cortical level , 22. A rInvestigating the neurophysiological correlates of abnormal somatosensory temporal discrimination in dystonia, Antelmi et al.  reportedOur observation that the STDT did not change either in patients with blepharospasm or in those with cervical dystonia, with or without clinical signs of spread, at the follow-up assessment suggests that STDT abnormalities in dystonia are representative of a background alteration in inhibitory mechanisms. We hypothesize that this alteration may be considered a “fingerprint” that remains stable over time and is a predisposing factor of the disease. Since cortical plasticity mechanisms rely on a dynamic balance between excitatory and inhibitory interneurons , 37, it Our findings showing that STDT values are unrelated to the severity of motor disturbances and that they do not change after 8 years despite the progression in dystonia severity suggest that abnormal STDT is not a marker of disease progression but is an endophenotypic marker of the disease. On the same line, STDT changes are present when dystonic features are not yet manifested in patients with increased blinking, a condition now considered to be a prodromal manifestation of blepharospasm , 39. DifA limitation of the present study may be the lack of a control group at follow-up. However, since STDT values in dystonic patients were already altered at baseline and since STDT values in dystonic patients remained unmodified at follow-up, we believe that the lack of a control group at follow-up unlikely affects the interpretation of our findings.In conclusion, the results of our study showing that STDT abnormalities in dystonia remain unmodified during the course of the disease suggest that the abnormal activity of inhibitory interneurons does not deteriorate further as the disease progresses.