Transcranial direct current stimulation (tDCS) is a promising method for altering cortical excitability with clinical implications in neuropsychiatric diseases. Its application in neurodevelopmental disorders especially attention-deficit hyperactivity disorder (ADHD), is in early stage and promising but its effectiveness has not been systematically examined yet. We conducted a meta-analysis on the effectiveness of tDCS on the most studied neuropsychological symptoms of ADHD, which is the first reported meta-analysis of tDCS studies on ADHD. Data from 10 randomized controlled studies (including 11 separate experiments) targeting inhibitory control, and/or working memory (WM) in ADHD were included. Results show that overall tDCS significantly improved inhibitory control. Sub-analyses further show that dorsolateral prefrontal cortex (dlPFC)  tDCS and anodal  tDCS significantly improved inhibitory control with a small effect size. Anodal dlPFC-tDCS had the largest significant effect on inhibitory control with a small-to-medium effect size. Additionally, a significant improving effect of tDCS on inhibitory control accuracy (but not response time) and WM speed (but not accuracy) were found. Overall, this meta-analysis supports a beneficial effect of tDCS on inhibitory control and WM in ADHD with a small-to-medium effect size. TDCS seems to be a promising method for improving neuropsychological and cognitive deficits in ADHD. However, there might be a dissociation between neuropsychological deficits and clinical symptoms of ADHD and therefore, the significance of this meta-analysis for clinical purposes is limited. Future studies should systematically evaluate the role of inter-individual factors  and stimulation parameters  on tDCS efficacy in ADHD population and examine whether benefits are long-term. Attention-deficit hyperactivity disorder (ADHD) is the most common neurodevelopmental disorder with an estimate of 11% prevalence in school-age children  and variA precise description of ADHD neuropathology is difficult to delineate due to its neuropsychological heterogeneity , 13, andPharmacological and non-pharmacological interventions have been among the most commonly used and recommended treatment options in ADHD. Pharmacological interventions can broadly be divided into stimulant and non-stimulant medications , 27. NonThe significant role of brain abnormalities in ADHD symptomology encouraged researchers to probe new treatment options that target ADHD symptoms by modulating, altering and remediating deficient neurocognitive brain functions. Transcranial direct current stimulation (tDCS) is a non-invasive, painless, and well-tolerated brain stimulation technique that has been gaining increased popularity in human neuroscience research in both healthy and clinical populations during last decade –35. It iTDCS has been applied for modulating a variety of cognitive functions –44 or imTo date, meta-analysis or specific systematic review is available for the effects of tDCS on ADHD. The present meta-analysis, therefore, aims to investigate the effectiveness of tDCS on neuropsychological deficits in ADHD. Moreover, we did further sub-analyses on the available studies in order to (1) evaluate overall and deficit-specific efficacy of tDCS in ADHD, (2) identify the brain regions that are prominently involved in ADHD pathophysiology tDCS response, and (3) examine stimulation parameters that are important for tDCS efficacy in ADHD. Since inhibitory control and WM deficiencies are among the major neuropsychological deficits of ADHD,  and mediOur meta-analysis follows the guidelines of the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA)  which co50) controlled or baseline-controlled design, (2) measured at least inhibitory control, and/or working memory performance, (3) reported data  which contained effect size values or mean and standard deviation values in order to calculate effect sizes. Participants in the studies were required to be between 3 to 18 years of age (for childhood and adolescence ADHD) and 18 to 65 years of age (for adult ADHD) and to have a clinical diagnosis of ADHD (any subtype) based on the Diagnostic and Statistical Manual of Mental Disorders (DSM) or meet accepted cut-offs on validated ADHD symptom rating scales. Studies which included patients under medication for ADHD treatment in either the control or the active arm were not excluded.To ensure a high level of methodological accuracy, only peer-reviewed published studies were included in our analysis. Only studies on humans using tDCS in experimental designs with the control condition  with reported full-text in English were retained. Studies were included if (1) they had a randomized placebo-  sham, 2) baseline or 3) sham and baseline (i.e. posttest–pretest tDCS vs posttest–pretest sham). When the effect size Cohen’s d was reported, the effect sizes were extracted directly from the selected articles. Otherwise, d was calculated using means and pooled standard error of mean, which were gathered from the results section, figures or tables. From these effect sizes, Hedges’ g values were calculated to correct for effect inflation due to small sample sizes [g values to determine the cumulative effect size (Ē) and 95% confidence intervals. Subsequently, the Z-statistic and p-value were calculated to investigate whether Ē differed significantly from zero.Hedges’ le sizes . In thisFor the main investigation on the effects of tDCS on inhibitory control in ADHD patients, three meta-analytic steps were performed. First, an unsigned analysis, in which the general effect of frontal tDCS, independent of polarity was analyzed. This analysis included 46 extracted effect size values. We further explored the effect of electrode montage by comparing tDCS setups that primarily targeted the dlPFC  or the rIFG . Second, a signed analysis was performed in which the effects of anodal  and cathodal tDCS  were determined separately. This analysis was then followed by an exploration of tDCS montage. Finally, since the majority of outcome measurements investigated both, accuracy  and speed (i.e. reaction time or reaction time variability) on inhibitory control tasks, separate analyses were performed for these variables . For the WM analyses, not enough observations could be gathered for cathodal tDCS stimulation (n = 2) and therefore no separate analyses were performed.2 distribution with n-1 degrees of freedom to determine whether the variance of effect sizes was greater than to be expected from sampling error [For all analyses, the sample distribution was checked for normality by the Kolgomorov-Smirnov test. Additionally, total heterogeneity  was tested against the χng error . To furtng error . Data weng error  and IBM In total, 11 separate experiments from 10 studies published from 2014—April 2018 were included in this meta-analysis. In 8 of 10 studies (or 9 of 11 experiments), effects of tDCS on inhibitory control was investigated , 68–74 aThe authors’ judgment on the risk of bias is displayed in p = 0.20) and total heterogeneity of the effect sizes was not significant . The fail-safe number indicated that 221 unpublished null-findings would be required to render the effect non-significant. Exploration of montage showed that only dlPFC stimulation  , but not rIFG stimulation  yielded a significant increase of accuracy rates in inhibitory control task performance.A significant cumulative effect size (Ē) of 0.197  was observed for a general tDCS effect on inhibitory control, taking polarity not into account Kolmogorov-Smirnov’s test of normality showed that the distribution of the effect sizes was not significantly different from a normal distribution (lower bound p = .20) and showed no significant heterogeneity . As for the stimulation polarity-independent analysis, this effect was driven by studies using a left and bilateral dlPFC montage , whereas the rIFG montage did not yield a significant effect . In contrast to anodal tDCS, cathodal tDCS did not show a significant overall effect .Subsequently, polarity-dependent effects were investigated. Studies using anodal tDCS showed a significant Ē of 0.232 , with a fail-safe number of 171 showing that anodal tDCS significantly improved inhibitory control. This sample was distributed normally . No significant cumulative effect was found for speed . For this last analysis, a deviation from normality was observed (p = 0.031). Results are summarized in p = .20) and no significant heterogeneity was seen . These results should be interpreted with caution, given the low sample size (N = 7). Moreover, results showed that tDCS did have no significant effect on accuracy of working memory task performance . Results are shown in No significant cumulative effect was observed for tDCS on working memory, without taking polarity into account . Also, no effect of tDCS was observed when only studies with an anodal montage were included . However, when separating outcomes for accuracy and speed, a significant effect of tDCS on speed was observed. TDCS led to a faster response time , with a fail-safe number of 17. The sample was normally distributed  tDCS has an overall significant cumulative effect on inhibitory control in ADHD with a small effect size, (2) when the targeted brain region is taken into account, only tDCS over the dlPFC had a significant effect on inhibitory control , but not tDCS over the rIFG, (3) when stimulation polarity was taken into account, only anodal, but not cathodal tDCS had a significant effect on inhibitory control, (4) when both polarity and targeted region are taken into account, only anodal tDCS of the dlPFC had a significant effect on inhibitory control with a small-to-medium effect size, (5) and when analyzing inhibitory control outcomes separately, tDCS had a significant cumulative effect on accuracy, but not speed . With regard to WM (6), tDCS had an overall significant effect only on performance speed but not on accuracy. In what follows we discuss tDCS effects on these two major target deficits, the stimulation parameters that could yield to larger effects, and finally clinical and methodological implications for future studies.The significant overall effect of tDCS on inhibitory control in ADHD is in line with a previous meta-analysis about the effects of this technique on a variety of cognitive functions  –80 and nAnodal dlPFC tDCS had the largest effect size  on inhibitory control in ADHD populations, whereas anodal rIFG tDCS had no significant effect. For stimulation over the dlPFC, both left and right dlPFC were targeted in different studies but the left dlPFC was almost always stimulated with the target electrode. First of all, this is in line with previous findings about significant involvement of the dlPFC in ADHD symptoms, especially executive dysfunctions , 18. InhSecondly, it highlights the importance of stimulation site for the tDCS effects on inhibitory control. Our findings showed that dlPFC tDCS and not rIFG tDCS is effective. Moreover, the target area of the reference electrode impacts on tDCS effects on inhibitory control. TDCS effects on inhibitory control were more effective when two specific regions were stimulated by the target and reference electrodes. The left dlPFC-right OFC montage was the most effective montage and all of the four experiments which used this protocol reported improved performance. In contrast, the left dlPFC-right dlPFC tDCS montage, which was used in two studies, did not improve any inhibitory control outcome measure. In two studies that targeted only one prefrontal region , inhibitory control was also improved see . ThirdlyAdditionally, the findings suggest that heterogeneity of ADHD subtypes and brain abnormalities should not be neglected in interpreting the tDCS effects. This heterogeneity could explain why rIFG tDCS was not as effective as dlPFC tDCS in the present analysis. For example, both, rIFG and left/right dlPFC abnormalities are shown to be associated with inhibitory control deficits in ADHD , 18, 53.Our meta-analysis showed that tDCS does not have an overall significant effect on WM performance accuracy in ADHD, although it led to significantly faster response time. To be more specific, it was shown that anodal left dlPFC tDCS, but not cathodal stimulation improved response time during WM performance in ADHD. This finding should be discussed considering physiological processes underlying inhibitory control and WM, task characteristics, and results of previous meta-analyses about tDCS effects on WM. First of all, this result shows a dissociation of tDCS effects on inhibitory control and WM. Such a dissociation has also been shown for neuropsychological deficits in ADHD . InhibitAnother factor that could be a source of variance of the tDCS effects on WM in the included studies is the difference of stimulation sites which is an important feature of tDCS efficacy. The stimulation montages of the studies on WM included anodal left dlPFC-right OFC tDCS (two experiments), left dlPFC-right dlPFC tDCS (two experiments), and left dlPFC-vertex tDCS (two experiments). Different montages used in these studies can explain the observed effects and may explain why some studies demonstrated no effects on WM accuracy. In four of the experiments, the reference electrode was positioned over regions that are involved in cognitive performance . In this case, it might be speculated that the cathodal return electrode compromises performance, and thus partially antagonizes anodal tDCS effects over the target region. The other two experiments used unilateral protocols that targeted the mere region of interest without positioning the cathodal return electrode over a potentially involved region and interestingly, in these studies both WM accuracy and RT improved, and prolonged effects outlasting the stimulation were also reported. Therefore, an electrode positioning which avoids such antagonistic effects might be advantageous.Recent meta-analyses and review articles about the effects of tDCS on cognitive functioning showed mixed results regarding memory tasks. For example, a recent systematic review of 188 trials reported significant effects of anodal tDCS on RT only for executive functioning tasks, but not memory tasks in both, healthy and neuropsychiatric populations . SimilarThis meta-analysis found that modulation of the activity of brain areas involved in the pathophysiology of ADHD with tDCS has a significant effect on response inhibition and WM, two major executive dysfunctions in ADHD , 53, 54.The findings of this meta-analysis have some important clinical and methodological implications to be considered for future tDCS studies in ADHD. The results of the included studies showed beneficial effects of tDCS in ADHD, and at the same time indicate that effects of tDCS on ADHD deficits (namely inhibitory control and WM) are strongly dependent on 1) individual and inter-individual factors  and 2) also stimulation parameters . For example, heterogeneous ADHD subtypes in the analyzed studies  might partially explain the non-significant effect of anodal rIFG tDCS on response inhibition, since dlPFC activity contributes to response inhibition in all ADHD subtypes , while the rIFG is assumed to be specifically involved in ADHD individuals with more hyperactivity subtypes. Therefore, the inter-individual variability is an important factor which generally affects the efficacy of tDCS  and mighAnother important implication regarding the clinical efficacy of tDCS in ADHD concerns stimulation parameters . The stimulation intensities applied in the included studies ranged from 1 mA (seven experiments) to 2 mA (two experiments) and two experiments applied tDCS with 1.5 mA intensity. Findings from other clinical populations showed that higher intensities of stimulation can result in more prominent symptom improvement, for example in tinnitus , or cognWith regard to stimulation duration, the length of stimulation duration varied from 8 min to 30 min and the longest duration of stimulation reported was five consecutive days of 30-min stimulation Tables  & 2. TheStimulation polarity is another important parameter that determines the efficacy of tDCS. The physiological mechanism of tDCS effects, depending on the polarity, is the induction of LTP- and LTD-like plasticity , 104. AnThe cortical target area or stimulation site, another important parameter, contributes to the clinical efficacy of tDCS in ADHD. The contribution of this parameter was specifically clear in the studies which investigated tDCS effects on ADHD WM deficits. Only when the potentially involved cortical region (left dlPFC in WM) was stimulated with the target electrode, both WM accuracy and RT significantly improved and the effects were long-lasting. In these cases, the reference electrode was placed over a non-contributing area . In contrast, when the reference electrode targeted homologous regions of the contralateral hemisphere  the effects were not present or reduced to RT improvement only. A comparable pattern but in a different way was observed for tDCS effects on inhibitory control. Here, tDCS effects were more effective when two specific potentially involved regions were stimulated by the target and reference electrodes. The left dlPFC-right OFC montage was the most effective montage and all of the four experiments which used this protocol reported improved performance. In contrast, the left dlPFC-right dlPFC tDCS montage, which was used in two studies, did not improve any inhibitory control outcome measure. This demonstrates that the target area or areas significantly contribute to the tDCS effectiveness in ADHD.To conclude, results from this meta-analysis support the cognitive benefits of tDCS in ADHD. However, for these cognitive benefits to be clinically useful, effects need to be sustained for longer durations. All of the studies included in this meta-analysis applied tDCS in an acute and short-term mode with no follow-up examination which does not allow to infer long-term efficacy of tDCS in improving ADHD neuropsychological deficits. Similarly, measuring inhibitory control and WM was done either during stimulation or right/shortly after intervention which hinders any robust conclusions about long-term effects of tDCS. One specific important note here is the dissociation between neuropsychological deficits and clinical symptoms of ADHD, which means improvement in inhibitory control and WM after or during tDCS does not say too much about the improvement of clinical symptoms. Moreover, applying statistically-proven blinding procedures, which was not reported in most of the included studies in this meta-analysis, is important for making firm conclusions about the clinical efficacy of tDCS. Therefore, the results of this meta-analysis should be interpreted with caution, especially when it comes to the clinical efficacy of tDCS in ADHD. Nevertheless, we need to note that the studies included in this meta-analysis are actually the first tDCS studies on ADHD that primarily aimed to investigate whether tDCS has any beneficial effects on ADHD symptoms or not. Despite short-term tDCS-induced cognitive benefits in ADHD, the clinical efficacy of this technique needs further investigation in follow-up designs and in comparison to other interventions. Moreover, it requires stimulation protocols optimization using the information about the individual neural activity associated with deficits and task execution  and general stimulation parameters .There are unique issues concerning the safety, applicability, and ethics of tDCS application in pediatric populations which is mainly due to limited available data from children compared to the adult population . HoweverDespite promising results and novelty, this meta-analysis has some limitations to be considered. First, despite that our meta-analysis found a significant effect of tDCS on neuropsychological symptoms (namely inhibitory control and WM) in ADHD populations, the efficacy of this method on other executive dysfunctions, and clinical symptoms cannot be directly derived from these results. Inhibitory control and WM were chosen because they are two common deficits examined in most ADHD-tDCS studies which allowed us to run a meta-analytic study. Secondly, although we showed that anodal tDCS over the dlPFC has significant effects on IC in ADHD, no effects were seen for cathodal tDCS and rIFG tDCS. However, given the small number of studies investigating cathodal/rIFG tDCS, these results have to be interpreted with caution. With increasing interest in the application of tDCS in ADHD, future research might be able to disentangle subtle protocol differences for ADHD subtypes. Thirdly, adaptation of stimulation protocols based on symptom subtypes, ADHD subgroups, specific cognitive deficits, and neuroanatomical differences is lacking in currently available studies and therefore, it is difficult to rate the potential of tDCS in ADHD.Future tDCS studies should systematically investigate the following lines of research, to reveal the real clinical potential of tDCS for ADHD treatment. First, preliminary data suggest beneficial effects of tDCS on other cognitive dysfunctions in ADHD including cognitive flexibility, problem-solving, selective attention, and hyperactivity symptoms involved in ADHS , 70, 109The findings of this meta-analysis of tDCS interventions in ADHD suggest an improvement of neuropsychological deficits  by tDCS. Stimulation polarity and target area are relevant for the efficacy of tDCS in ADHD. Anodal dlPFC tDCS had a significantly superior effect on inhibitory control compared to cathodal/sham stimulation and anodal rIFG tDCS. TDCS significantly increased response accuracy of inhibitory control performance and decreased response time in WM tasks. Although our findings suggest improving effects of tDCS in ADHD neuropsychological deficits, the clinical utility of tDCS cannot be firmly rated with the currently available findings. Application of this method as a therapeutic intervention will require optimizing stimulation protocols based on general stimulation parameters and individual and inter-individual factors for improvement of clinical efficacy, exploration of clinical symptoms in addition to surrogate parameters, and achievement of sustained clinical benefits by tDCS over longer durations of time. Thus, future research is needed to more thoroughly explore and refine optimal stimulation parameters required for tDCS-based cognitive improvement and implementing robust experimental designs in different ADHD subtypes. Broadly speaking, the potential for tDCS as a non-invasive brain stimulation technique to safely improve neuroplasticity and treat neurological and neurodevelopmental disorders is encouraging. Future studies utilizing tDCS will further increase our understanding of neural networks and how to treat their pathological states in ADHD and other neurodevelopmental disorders including autism and learning disabilities.S1 Table(DOC)Click here for additional data file.


Gadus morhua). Using cloning, sequencing and gene expression analyses, we characterized the Atlantic cod viperin at the nucleotide and hypothetical amino acid levels, and its regulating factors were investigated. Atlantic cod viperin cDNA is 1,342 bp long, and its predicted protein contains 347 amino acids. Using in silico analyses, we showed that Atlantic cod viperin is composed of 5 exons, as in other vertebrate orthologs. In addition, the radical SAM domain and C-terminal sequences of the predicted Viperin protein are highly conserved among various species. As expected, Atlantic cod Viperin was most closely related to other teleost orthologs. Using computational modeling, we show that the Atlantic cod Viperin forms similar overall protein architecture compared to mammalian Viperins. qPCR revealed that viperin is a weakly expressed transcript during embryonic development of Atlantic cod. In adults, the highest constitutive expression of viperin transcript was found in blood compared with 18 other tissues. Using isolated macrophages and synthetic dsRNA (pIC) stimulation, we tested various immune inhibitors to determine the possible regulating pathways of Atlantic cod viperin. Atlantic cod viperin showed a comparable pIC induction to other well-known antiviral genes  in response to various immune inhibitors. The pIC induction of Atlantic cod viperin was significantly inhibited with 2-Aminopurine, Chloroquine, SB202190, and Ruxolitinib. Therefore, endosomal-TLR-mediated pIC recognition and signal transducers  downstream of the TLR-dependent pathway may activate the gene expression response of Atlantic cod viperin. Also, these results suggest that antiviral responses of Atlantic cod viperin may be transcriptionally regulated through the interferon-activated pathway.Viperin is a key antiviral effector in immune responses of vertebrates including the Atlantic cod ( As iromoters , 10.viperin is induced via IFN-dependent and independent pathways, both of which may be activated by detection of viruses or dsRNA through a member of the RLR family and activation of transcription factors  -associated, IFN-inducible (Viperin), also known as Radical S-adenosyl methionine (SAM) domain-containing 2 (RSAD2) or Virus-induced gene 1 (VIG1), is an antiviral protein, highly inducible by pIC, lipopolysaccharide (LPS), viruses, and bacteria , 12. The3, IRF3) . Mammali3, IRF3) . Viperin3, IRF3) .viperin was also observed in teleosts  was conducted in 50 μl reactions using the Advantage 2 Polymerase, Advantage 2 PCR buffer, dNTP Mix (Clontech), and GSPs  for 16 h at 37°C. Thereafter, colonies were taken using blue/white selection and cultured in LB supplemented with ampicillin (100 μg ml−1) at 37°C overnight. Plasmid DNA was extracted using QIAprep Spin Miniprep Kit (Qiagen), following the manufacturer's instructions. The insert sizes of recombinant plasmids were checked using EcoRI (Invitrogen) digestion and agarose gel (1%) electrophoresis. Four colonies from each 5′ and 3′ RACE products were used for sequencing performed at the Genomics and Proteomics (GaP) facility, Core Research Equipment and Instrument Training (CREAIT) network, Memorial University of Newfoundland. Sequencing was conducted using an ABI 3730 DNA Analyzer with BigDye Terminator v3.1 Cycle Sequencing Kit .PCR products were examined on 1.2% agarose gel, and then were extracted using the QIAquick Gel Extraction kit (Qiagen) according to the manufacturer's recommendations. TA cloning of gel-extracted PCR products was performed using pGEM-T-Easy vector  at 4°C overnight, using the manufacturer's instructions. Recombinant plasmids were transformed into Subcloning Efficiency DH5α Competent Cells   following the manufacturer's instructions. The transformed cells were incubated in 300 μl of SOC medium (Invitrogen) for 1 h at 37°C with shaking (~225 rpm), and then cultured on Luria broth (LB)/agar plates containing 100 μg m1viperin cDNA. GSPs amplifying the open reading frame (ORF) were designed  and cDNA of pIC-stimulated Atlantic cod macrophages  in a 50 μl reaction. The PCR reaction was composed of 2 μl of cDNA , 0.5 μM each of forward and reverse GSP, 5 μl of 10X TopTaq PCR buffer, 1.25 U of TopTaq DNA Polymerase, and 200 μM of each dNTP, with the following PCR program: initial denaturation of 3 min at 94°C, followed by 30 cycles of , and 1 final extension cycle at 72°C for 10 min. The size of the resulting PCR product was determined by gel electrophoresis (1.2% agarose) alongside a 1 kb Plus Ladder (Invitrogen).Lasergene 7.20 software  was used to acquire overlapping sequence from 5′ and 3′ RACE products and assemble the full-length gned see  to verifviperin was aligned with genomic DNA sequence of Atlantic cod obtained from the Ensembl (http://www.ensembl.org) and Centre for Ecological and Evolutionary Synthesis (CEES: http://cees-genomes.hpc.uio.no) Genome Browsers. The AA sequences of Viperin of other fish species, as well as other vertebrate and invertebrate species (see http://pfam.xfam.org/) (The AA sequence of Atlantic cod Viperin was predicted based upon assembled cDNA sequence using the SeqBuilder software of the Lasergene package (DNASTAR). To map the gene structure and determine intronic regions and genomic location, the cDNA sequence of cies see , were cocies see , 38. Theam.org/) . The dedviperin and its conserved synteny with other species were mapped using the Genomicus database (http://www.genomicus.biologie.ens.fr), powered by the Ensembl database. The neighboring genes and genomic location of Atlantic cod viperin were also confirmed using CEES Genome Browser (http://cees-genomes.hpc.uio.no).The neighboring genes of Atlantic cod viperin, putative transcription factor binding sites (TFBSs) were predicted in the proximal promoter region of this gene. The 1,000 bp 5′-upstream of the transcription start site of Atlantic cod viperin were taken from genomic DNA sequence, available at CEES Genome Browser (http://cees-genomes.hpc.uio.no/). Putative TFBSs were identified using the vertebrates' profile of the TRANSFAC database (http://genexplain.com/transfac/). This prediction was performed using the default parameters  suggested by the TRANSFAC database, and the predicted TFBSs (core score > 0.8) with putative functions in immune responses were selected and presented herein.To gain insight into transcriptional regulation of Atlantic cod Mus musculus) Viperin crystal structures were used as templates for homology modeling . PyMOL v1.7.6 (http://www.pymol.org/) was used to visualize templates and models. Atlantic cod Viperin was computationally modeled using default parameters of I-TASSER (http://zhanglab.ccmb.med.umich.edu/I-TASSER/)  Viperins. Both [4Fe-4S] cluster and Radical SAM analog  were manually placed in the catalytic pocket of the Atlantic cod Viperin. The surface charge and the isoelectric point of Atlantic cod and full-length mouse Viperin were estimated using the PDB2PQR server (http://nbcr-222.ucsd.edu/pdb2pqr_2.0.0/). Prediction of natively disordered regions of Viperin was conducted using the default parameters of the Protein disorder prediction server (PrDOS) website (http://prdos.hgc.jp/cgi-bin/top.cgi).The recently-described partial mouse (modeling –43. The TASSER/) –43. Twen3 flow-through tanks (one tank for broodstock fish and one tank for fish used for tissue sampling and macrophage isolation) with optimal conditions  in the Dr. Joe Brown Aquatic Research Building (JBARB) of the Ocean Sciences Centre (OSC). The fish [2.29 ± 0.42 kg (mean ± SE)] used for tissue sampling and macrophage isolation were fed 3 days weekly  with a commercial diet . The broodstock fish were fed mackerel, herring and squid supplemented with vitamins 2 days per week before and during spawning season. Fish  were fasted 24 h and euthanized with an overdose of MS222  prior to the sampling. All procedures applied in the current investigation were approved by the Memorial University of Newfoundland's Institutional Animal Care Committee, according to the guidelines of the Canadian Council on Animal Care.The Atlantic cod used in this experiment were kept in two 21 mviperin in various tissues of adult Atlantic cod, four individuals  were used. Following euthanasia and dissection, samples were collected from 19 different tissues  of each individual; the samples were immediately flash-frozen using liquid nitrogen and kept at −80°C until RNA extraction.To evaluate the constitutive transcript expression of −1 flow rate and gentle aeration. The fertilized eggs were incubated and kept in these tanks until yolk-sac absorption stage  at 5.5–6.1°C and under an ambient photoperiod. The developmental stage of embryos was determined daily  or larvae (~0.4 ml) were sampled daily  from each incubator tank , using 500 μm Nitex. The collected (~180 embryos or larvae per sample) samples from each tank were then flash-frozen using liquid nitrogen and kept at −80°C until RNA extraction.The floating fertilized eggs were automatically collected after overnight communal spawning. Then, 1.4 L of fertilized eggs   were distributed into three 50 L conical incubator tanks (350 ml of eggs per tank) with 25 L hed daily . The emb7 cells (in 2 ml L-15+) per well (16 wells per fish). The cells were cultured in Leibovitz's L-15+  overnight at 10°C. The non-adherent cells were then removed by washing the culture dishes 3 times with L-15+.Atlantic cod macrophages were isolated from the head kidneys of 5 individuals as described in Eslamloo et al. , 45. Allin vitro-based studies in fish . Moreover, macrophages from each individual were subjected to PBS, DMSO (0.57 μl ml−1 of L-15+), or AcOH (0.17 μl ml−1 of L-15+) as control conditions . The cells were incubated with inhibitors for 1 h. Afterward, macrophages from each fish under different inhibitor treatments or controls (2 wells per group) were exposed to either 50 μg ml−1 pIC (−1 of L-15+). The culture medium of all groups in this study contained an identical level of PBS . The macrophages from each individual were incorporated into all experimental groups . Our previous study determined the time-dependent pIC responses of Atlantic cod macrophages , and the stock solutions were prepared using the manufacturer's instructions. The effective doses of different immune inhibitors used in this experiment were obtained from previously published  in fish –49, excean cells . 2-Aminoan cells . Chloroqan cells , 47. To an cells . The pICml−1 pIC  or PBS  following the manufacturer's instructions. RNase-free  ceramic mortars and pestles were used to homogenize the firm tissues , whereas other tissue and developmental samples were TRIzol-lysed using RNase-Free Disposable Pellet Pestles (Fisherbrand). Then, the homogenates of tissue and developmental samples were passed through QIAshredder (Qiagen) spin columns and used for RNA extraction following the manufacturer's instructions. The TRIzol-lysed macrophage samples were also processed for RNA extraction according to the manufacturer's recommendations.Prior to purification, RNA samples (≤50 μg) in all experiments were treated with 6.8 Kunitz units of DNaseI (Qiagen) with the manufacturer's buffer  for 10 min at room temperature to remove residual genomic DNA. RNA purification of adult tissue and developmental series samples  was performed using the RNeasy Mini Kit (Qiagen), whereas macrophage samples were purified using the RNeasy MinElute Cleanup Kit (Qiagen) according to the manufacturer's instructions. RNA concentration and quality were assessed using NanoDrop spectrophotometry (ND-1000), and RNA integrity was assessed by agarose gel electrophoresis (1% agarose). All column-purified RNA samples subjected to gene expression analyses in this study showed acceptable purity  and integrity .cDNA synthesis was performed using RNA of each sample , random primers , 1 μl of dNTPs  and M-MLV reverse transcriptase  in the manufacturer's first-strand buffer  and DTT  at 37°C for 50 min following the manufacturer's instructions.The qPCR assays in the current study were designed and performed on the basis of the Minimum Information for Publication of qPCR Experiments (MIQE) guidelines . The qPCThe primer sequences in this study were obtained from our previous study  see Tab. Prior tcyclophilin a (cypa), 60S acidic ribosomal protein P1(rplp1), 60S ribosomal protein l4-a (rpl4a), beta-2 tubulin (tubb2), heat shock cognate 70 kDa (hsc70), eukaryotic translation initiation factor 3 (eif3), and eukaryotic elongation factor 1 α (eef1a)], embryonic and early larval stages  and macrophage stimulation  experiments was assessed in duplicate using 50% of the samples from each experiment. The expression results were subjected to geNorm analysis using qBase software as in Eslamloo et al. , embryonic and early larval development (eif3 and tubb2), and macrophage stimulation (rplp1 and eef1a) experiments. In addition to viperin, the expression levels of Atlantic cod ifng, interferon stimulated gene 15-1 (isg15-1), RNA helicase lgp2  and interleukin 1 beta (il1b) were measured in macrophage samples. Since ifng, isg15-1 and lgp2 play important roles in antiviral responses  value variations < 0.5] as well as no-template controls. ViiA7 software v1.2.2 (Applied Biosystems) was applied to calculate the relative quantity (RQ) values, relative to a calibrator sample  for the gene of interest, using the CT values  and the amplification efficiency of each primer pair (see The qPCR assays for samples of each experiment were performed in triplicate using 4 ng (macrophage samples) or 10 ng  of input total RNA per reaction. The performance of assays between qPCR plates used in a given experiment was tested using an inter-plate linker sample  or vertebrate classes . Also, the radical SAM domain of Atlantic cod Viperin contained a conserved SAM binding motif (CXXXCXXC) (see T. thermophila (see Oncorhynchus mykiss) (82%) and Orange-spotted grouper (Epinephelus coioides) (79%). The phylogenetic tree of Viperin was constructed using a MSA of putative orthologous sequences from various species   and Cypriniformes ] were clustered together  within the Protacanthopterygii superorder were clustered together. The Viperin of the ciliated protozoan, T. thermophila, formed a separate branch from the other species in the phylogenetic tree. Interestingly, Viperin of amphioxus (Branchiostoma japonicum) and Pacific oyster (C. gigas) were clustered together and separated from other species.The multiple alignment of putative AA sequences of Atlantic cod Viperin and orthologous sequences from other eukaryotic species is shown in XXC) see . Howeverhila see , whereasmammals) . As expetogether . MoreoveIn silico analysis of the 5′-upstream region was used to predict the immune-related putative TFBSs that may play roles in regulating the expression of Atlantic cod viperin. As shown in viperin. Moreover, GAS and ISRE, which are the binding motifs for IFNG activation factor  and IFN-stimulated gene factor 3 (ISGF3), respectively, were identified in the proximal promoter region of Atlantic cod viperin.6-barrel folding  were used as templates for homology modeling prediction of full-length Atlantic cod and mouse Viperins . Compari folding . The CXXThe majority of the AA differences between the Atlantic cod and mouse Viperins are located in the α-helices and loops forming the surface of the protein, while the core of the protein forming the potential catalytic pocket cavity remained remarkably conserved  during early developmental stages of Atlantic cod. The expression of the normalizer genes was slightly lower . Thereupon, viperin levels dropped to a non-detectable level during gastrula and early segmentation stages (days 4–7). In other words, Atlantic cod viperin was not detected at the onset of zygotic gene expression, suggesting that viperin is a maternal transcript. Atlantic cod viperin expression increased during the segmentation stage, and then appeared to decrease after hatching.qPCR revealed ly lower  during vviperin was assessed in 19 different adult tissues. As shown in viperin transcript was seen in Atlantic cod blood, which was significantly higher than all other tissues. Interestingly, the levels of viperin transcript in immune-related tissues, notably head kidney and spleen, were significantly lower than that in blood. Additionally, viperin transcript had significantly higher expression in gill and pyloric caecum compared to the dorsal skin and liver. The transcript expression of viperin was relatively, but not significantly, lower in the skin, muscle and fin tissues compared with some digestive tissues .The constitutive expression of Atlantic cod viperin. As shown in viperin compared to the AcOH-matched control. There was no significant difference between group-matched PBS and AcOH controls, showing that viperin suppression in the 2-AP group was not influenced by the AcOH in which 2-AP was dissolved. CHQ also inhibited the viperin transcript expression in the pIC-stimulated Atlantic cod macrophages compared to the DMSO-matched vehicle control, indicating that TLR-activated pathways play an important role in the Atlantic cod viperin antiviral response. The expression of viperin transcript in pIC-treated macrophages was likewise significantly reduced in the S90 group compared to its pIC-treated DMSO vehicle control, suggesting that inhibition of the MAPK pathway strongly affects Atlantic cod viperin induction. Finally, our results revealed that Atlantic cod viperin may be a JAK1/JAK2-activated gene downstream of the IFN pathway, as there was a strong repression in the RUX-exposed pIC group compared to the pIC-treated DMSO vehicle control. On the other hand, there was no significant difference between the RESV  group and its DMSO-matched control. Also, with respect to the role of ifng in innate immune responses and viperin induction, the expression levels of ifng as well as two important IFN-induced genes, i.e., isg15-1 and lgp2, were assessed in the macrophage samples  compared to the DMSO control group (13.5-fold pIC induction). Unlike isg15-1 and lgp2, though, there was no significant difference between the PBS control and pIC sub-groups of RESV treatment for ifng, indicating the suppressed induction of this gene by RESV. These findings suggest that, while the expression of all genes studied herein is regulated through PKR, TLR, MAPK and IFN pathways, only ifng shows a significant NFKB-dependent transcriptional activation. None of the inhibitors used in this study influenced viperin, ifng, isg15-1, or lgp2 expression in non-stimulated macrophages, and the inhibitors only suppressed the expression of these antiviral genes in the pIC group compared with pIC-stimulated controls . This suggests that the constitutive expression of these antiviral biomarkers in Atlantic cod macrophages is regulated independent of the inhibited pathways. The expression of il1b was measured as an antibacterial and pro-inflammatory biomarker to examine the specificity of the immune inhibitors used in the current study. The transcription of il1b was not induced by pIC stimulation in any of the treatments  and consists of 6 exons. Exon 5 of Atlantic cod viperin is the shortest, whereas exons 1 and 6 are relatively longer compared to the other exons. The transcript size of Atlantic cod viperin is comparable with other fish species such as red drum (Siniperca chuatsi) (S. chuatsi), and Ara (Niphon spinosus)  (M. musculus) , avians  and mammals   , Chinesepinosus) . As in Ared drum  and humared drum  were reprin fish , 55, chi gallus) , and mouusculus) , includeodytes)] , 59. TakAs expected, the phylogenetic tree showed that the relatedness of Viperin putative orthologs appears to agree with taxonomic classification. Previous studies conducting MSAs and molecular phylogenetic analyses of Viperin in different species obtained comparable results to the current study , 59–61. Anas platyrhynchos)   and red hynchos) , a consehynchos)  in the Ahynchos) . The conhynchos) , 63, 64,The radical SAM Superfamily domain is found in hundreds of proteins that play a wide range of roles . Viperinviperin was found as a weakly-expressed gene during embryonic development. However, the expression of viperin was higher in mixed cleavage stage until mid-blastula  compared with subsequent embryonic stages , showing the existence of viperin transcript prior to the onset of zygotic gene expression. This embryonic expression profile of viperin alongside its presence in adult fish gonads suggests that viperin is a maternal transcript in Atlantic cod. Maternal molecules  play an important role in defense responses of fish during early life stages  involved in innate immune responses were previously identified in Atlantic cod . The transition from maternal to zygotic gene expression occurs at mid-blastula stage  -induced viperin transcript was reported in eyed eggs and hatching fry of rainbow trout (viperin transcript increased in 48-h post-fertilization (hpf) larvae of zebrafish and 24-hpf D-veliger larvae of oyster infected with herpes simplex virus 1 (HSV-1) and Ostreid herpesvirus (OsHV-1), respectively  of Atlantic cod were reported to increase during hatching; it was suggested that this induction may be involved in preparing cod embryos at the defensome level to combat environmental pathogens that may be encountered post-hatch  , 79, 80.ow trout . Additioectively , 82. We st-hatch .viperin varied among different tissues. Atlantic cod viperin was strongly expressed in blood and, interestingly, viperin levels in immune-related tissues  were significantly lower than in blood. Likewise, the expression of viperin in the blood of red drum (Larimichthys crocea)  was higher than some tissues . The intestinal expression of viperin was previously reported in different species    and duck crocea)  was high crocea) , and it nd duck) , 59, 60.nd duck) , the telnd duck) , and vipescribed , and furviperin and other well-known antiviral genes . In addition to these genes, the expression of il1b was assessed, as a pro-inflammatory and antibacterial biomarker, to check if the inhibitors used in this study have gene-specific effects. Previous studies have documented the induction of Atlantic cod viperin in pIC-exposed macrophages or larval cell line (ACL cells) as well as the spleen of pIC-injected fish  stimulation  of rainbow trout  embryo cells  (il1b in gilthead seabream (Sparus aurata) macrophages (myeloid differentiation primary response 88 (myd88) and il6] in peripheral blood leukocytes of Japanese flounder  in response to pIC in Atlantic cod macrophages  reflects the specific effects of CHQ on the antiviral response of Atlantic cod macrophages. Collectively, it seems that CHQ influences intracellular TLRs of teleosts, and that activation of Atlantic cod viperin, ifng, isg15-1, and lgp2 is highly dependent upon the endosomal recognition of pIC.and lgp2 . In agreow trout  and mx pyo cells . 2-AP isyo cells ; howeveryo cells . The inhin human . Taken t., TLR3) . CHQ can., TLR3) . However., TLR3) , 98. The., TLR3) , to decrrophages  and to bflounder . The exprophages . Slight il1b and tnfa) in head kidney leukocytes of Atlantic salmon .S90 is known to inhibit the activity of p38 MAPK . S90 wasc salmon . Generalc salmon . Thereforophages . Nonetherophages . In Atlarophages . While tviperin, RUX significantly suppressed the expression of ifng, isg15-1, and lgp2 in the present study, suggesting the activation of these genes downstream of JAK1/JAK2-dependent pathway. There is no report on RUX-based inhibition of IFN-dependent responses of fish species, although RUX has been reported to significantly reduce the production of IFNG in mice  identified herein are compatible with the JAK1/JAK2-dependent Atlantic cod viperin transcript expression, these in silico results need to be experimentally validated by future studies. ISRE-regulated activation, as well as IFN receptor (IFNR)- and IRF-dependent induction of viperin have been described for mammalian macrophages . Moreover, two putative IFN-induced genes  studied herein showed expression profiles that were similar to that of viperin, suggesting that these genes may share signaling pathways  activating their pIC response. Conversely, il1b in this study showed a different expression pattern and its expression increased in the RUX group compared to the DMSO control group. Likewise, RUX-mediated JAK inhibition increased the expression of pro-inflammatory cytokines  in mouse macrophages (ifng and other assessed genes. There were significant correlations (p < 0.0001) between the expression of Atlantic cod ifng and other antiviral genes , but no correlation was seen between ifng and il1b expression . This suggests that the IFN pathway plays important roles in transcriptional regulation of Atlantic cod viperin, isg15-1 and lgp2. Additionally, the repressed antiviral response of Atlantic cod viperin, isg15-1 and lgp2 by other immune inhibitors  may also be attributed to their influence on IFNG secretion, as ifng expression was significantly influenced by these inhibitors. Taken together, our results, alongside previous studies, suggest that IFN-dependent regulation of viperin may be conserved among vertebrates. However, a previous study suggested that the pIC induction of rainbow trout viperin may be independent of protein synthesis  type I and II IFNs with the IFN receptors , 108. As in mice . In mamm in mice  and the  in mice . Similar. However, RESV did not significantly change the expression of Atlantic cod viperin transcript in response to pIC herein. Conversely, the pIC response of Atlantic cod ifng was suppressed by RESV. Also, there was a decrease in pIC induction of isg15-1 and lgp2 in the RESV group compared to the pIC-stimulated DMSO vehicle control group. In agreement with these results, RESV suppressed virus-induced IFNG expression in mice  phosphorylation , and it  in mice . These rviperin is an evolutionarily conserved gene that has similar gene organization and flanking genes to its putative orthologs in other vertebrates. Atlantic cod Viperin exhibits a close phylogenetic relationship with Viperin of other teleosts. A highly-conserved protein structure reported herein suggests a functional role for the Atlantic cod Viperin comparable with that of other Viperin orthologs. Atlantic cod viperin transcript showed a tissue-specific constitutive expression and was most strongly expressed in the blood. The inhibitory effects of 2-AP, CHQ, and S90 on pIC induction of viperin transcript in Atlantic cod macrophages revealed that the expression of this gene may be dependent upon PKR, intracellular TLRs and MAPK, and/or possibly the factors  activated downstream of these pathways. Also, RUX-associated suppression of Atlantic cod viperin, alongside the GAS and ISRE motifs predicted in the proximal promoter of this gene and its significant correlation with ifng expression in response to different immune inhibitors, suggest the IFN-mediated regulation of Atlantic cod viperin.In conclusion, the present study showed that Atlantic cod KE took a lead role in gene characterization, sequence analyses, experimental design, sampling, cell isolation, qPCR assays, data analyses, data interpretation, and the writing of manuscript draft. AG helped with RNA extraction, performed computational modeling of Viperin proteins and took part in manuscript writing. XX and SMI helped with sequence characterization, tissue sampling and RNA extraction. ML took part in data analyses and interpretation as well as manuscript writing. MLR was involved in experimental design, data analyses, and data interpretation, and took an active role in manuscript writing. All authors read and approved the final manuscript.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Attention‐deficit/hyperactivity disorder (ADHD) frequently co‐occurs with depression, and outcomes are poor when both are present. Little is known about whether depression symptoms present differently in ADHD compared to the general population, or how reliable young people with ADHD are at reporting these symptoms. This study aimed to describe depression symptoms in a clinical ADHD sample compared to a population sample, and compare self‐reports of depression symptoms with parent‐reports.n = 1460). Within both samples, child‐ and parent‐reported depression symptoms were compared.Two hundred and forty‐nine children with ADHD and their parents completed follow‐up questionnaires around 5 years after taking part in a Cardiff University ADHD study. Child depression symptoms were measured using parent‐ and child‐reported Mood and Feelings Questionnaires (MFQ) and compared to a population sample with MFQ data . The most common symptoms in both samples included irritability, restlessness and concentration difficulties, with core depression symptoms such as feeling miserable/unhappy also prominent. Within the ADHD sample, but not the population sample, children reported depression symptoms less frequently than their parents.Young people with ADHD are at high risk of experiencing symptoms of depression but may under‐report the severity of their symptoms. Obtaining parent reports of depression symptoms in this group may be important to avoid missing key indicators of risk. Depression symptoms, as measured by the Mood and Feelings Questionnaire, are common in children and adolescents with ADHD.The profile of depression symptoms in ADHD is similar to that in the general population.Children with ADHD report lower levels of depression symptoms than their parents, the opposite pattern to the general population.Children with ADHD may under‐report the severity of their own symptoms of depression.Attention‐deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by hyperactive‐impulsiveness and inattention APA, . In addiIt is important to recognise children with ADHD who present with symptoms of depression, as its presence alongside ADHD is associated with poorer academic and social functioning  compare the prevalence of depression symptoms, (b) compare the depression symptoms most commonly reported, and (c) examine differences between child‐ and parent‐reports of depression symptoms.This study used a subsample of children originally recruited as part of the Cardiff University Study of ADHD Genes and Environment (SAGE). The SAGE study consisted of 696 children and adolescents recruited between 2007 and 2011 from child psychiatry and paediatric clinics across South Wales. The children of this original sample were aged 6–18 years (mean = 10.9 years), 84% were male, and all were of British Caucasian origin. All had a clinical and research diagnosis of ADHD. To examine the prevalence of depression symptoms in this sample in adolescence, follow up postal questionnaires (including the Mood and Feelings Questionnaire) were sent out to a subsample of 434 participants in 2014–2015. The subsample was selected on the basis that children were aged 12 years or under at the time of the initial data collection (mean = 9.0 years) and that the family had consented to be contacted for future research at the time of the original study. Based on data available from a structured clinical interview at follow up (the Development and Well Being Assessment (DAWBA),  for completion, from which there were Ethical approval was obtained for the SAGE study from the Wales Multicentre Research Ethics Committee (MREC). Written informed consent from parents and assent from children (or consent if aged 16 and older) were obtained for all individuals. The twin study was approved by Wales MREC and Northwest MREC and consent was obtained from all participants following completion of the questionnaire.Parents and children completed the Mood and Feelings Questionnaire (MFQ)  were missing for an individual, the total score was left as missing. Where <10% (≤3) of MFQ items were missing, a mean score of the completed items was imputed allowing a total to be calculated.Total parent‐ and child‐reported MFQ scores were calculated for each sample and compared using independent sample In order to identify the most frequently endorsed items, a mean score was calculated for each MFQ item (both for parent and child measures). This allowed items to be ranked from the most commonly endorsed to the least commonly endorsed. The most commonly reported symptoms in the ADHD sample were then compared to the population sample. In order to assess agreement between parent and child reports in each of the samples, the Pearson's correlation between total parent and child MFQ score was calculated. In addition, the kappa coefficient of agreement was calculated for each individual MFQ item (‘true’ and ‘sometimes’ vs. ‘not true’).As the ADHD sample was older than the population sample (mean 14.6 vs. 12.8 years), analyses were repeated excluding the oldest participants from the ADHD sample (age ≥16 years) making the mean ages more comparable (13.1 vs. 12.8 years). As there were prominent gender differences between the two samples, analyses were also repeated for boys and girls separately.Data were analysed using SPSS version 20.In the ADHD sample, the mean age was 14.6 years (range 8–20 years) and included 81.9% males and 18.1% females. In the population sample, the mean age was 12.8 years (range 8–17 years)  versus 23.5 (SD = 15.2) on the parent‐rated measure (t(244) = 1.873, p = .066) and 25.0 (SD = 15.0) versus 20.2 (SD = 15.4) on the child‐rated measure (t(168) = 1.51, p = .132), but MFQ score was not associated with age.Those returning questionnaires were slightly younger and less likely to be from low income families than those who did not return them. However, there were no differences in child or parent psychopathology at study baseline between responders and non‐responders. The mean total MFQ score was higher in girls than in boys with a mean of 28.2  versus 8.8 (SD = 8.01) on the parent rated measure (t(1437) = 2.38, p = .017) and 12.9 (SD = 10.54) versus 10.6 (SD = 9.61) on the child rated measure (t(905) = 3.38, p = .001).In the population sample 1460 families had MFQ data available for twin 1 (1456 parent and 913 child), 909 of whom had both parent‐ and child‐report data. Nine families were excluded from the analysis due to >10% of MFQ items missing from either the parent or child report, leaving a total of 1451 families, t(269.9) = 14.94, p < .001, mean cMFQ score = 21.0 vs. 11.9, t(197.5) = 7.46, p < .001). These results remained similar when the oldest children were removed from the ADHD sample  = 13.16, p < .001, mean cMFQ score = 20.4 vs. 11.9, t(117.8) = 6.0, p < .001) and when the sample was split by gender  = 13.2, p < .001; mean cMFQ 20.2 vs. 10.7, t(80.2) = 6.93, p < .001. In girls: mean pMFQ 28.2 vs. 9.9, t(45.8) = 7.84, p < .001; mean cMFQ 25.0 vs. 12.9, t(28.5) = 4.24, p < .001).As shown in Table χ2 = 285.24, p < .001; child‐report 32.4% vs. 10.5%, χ2 = 56.73, p < .001).The proportion scoring above the clinical cut‐off was also much higher in the ADHD sample than in the population sample  were the lowest scoring symptoms on both parent‐ and child‐report. The frequency at which each MFQ item is reported for pMFQ and cMFQ is detailed in Table For both parent‐ and child‐report, the highest scoring symptom was feeling grumpy/irritable with parents followed by feeling miserable or unhappy. The lowest scoring symptom for both was thoughts of killing self. The frequency at which each MFQ item is reported for pMFQ and cMFQ is detailed in Table p < .001). When assessing agreement, for the majority of individual MFQ items, parents were more likely to score the symptom as present than the child. The items with the highest agreement included thoughts of killing self, not having fun at school and crying a lot. Items with the lowest agreement included restlessness, difficulty concentrating and feeling grumpy with parents. The kappa coefficients ranged from 0.634 to 0.100 (detailed results available on request).Pearson's correlation for total pMFQ and cMFQ in the ADHD sample was 0.642 (p < .001). When assessing agreement, unlike for the ADHD group, the children were more likely to score symptoms as present than their parents. The items with the highest agreement included feeling miserable or unhappy, crying a lot and thoughts of looking ugly. Items with the lowest agreement included sleeping more than usual, talking more slowly than usual and moving and walking more slowly than usual. The Kappa coefficients ranged from .358 to .102.Pearson's correlation between total pMFQ and cMFQ score was 0.471  than for the pMFQ (≥21) , affective disorders are more common in females . Written informed consent from parents and assent from children (or consent if aged 16 and older) were obtained for all individuals. The twin study was approved by Wales MREC and Northwest MREC and consent was obtained from all participants following completion of the questionnaire.


This study aimed to explore attentional patterns among children with inattentive attention-deficit/hyperactivity disorder (ADHD-I) and children with typical development (TD), using a latent class analysis (LCA). Patterns of brain connectivity were also explored. The sample comprised 29 ADHD-I and 29 TD matched children. An LCA was conducted to reclassify subjects according to their attentional performance, considering cognitive measures of attention and behavioral symptoms, regardless of group of origin. The new clusters were then compared in respect to brain white matter measurements (extracted from diffusion tensor imaging). Participants were rearranged in 2 new latent classes, according to their performance in an attention task and the results of behavioral scales, resulting in groups with more homogeneous attentional profiles. A comparison of the 2 new classes using the white matter measurements revealed increased fractional anisotropy in the left inferior fronto-occipital fasciculus and left inferior longitudinal fasciculus for the class composed by participants with a higher risk of attentional problems. The findings indicated that it was possible to observe variability regarding neuropsychological profile, accompanied by underpinning neurobiological differences, even among individuals with the same disorder subtype - inattentive ADHD. This specific data-driven clustering analysis may help to enhance understanding of the pathophysiology of the disorder's phenotypes. Studies exploring cognitive, behavioral, or emotional patterns, as well as neurobiological or genetic traits among diagnostic conditions and typically developing individuals are becoming a trend in neuropsychiatry –4. In 20Growing evidence has established that attention-deficit/hyperactivity disorder (ADHD) is a highly heterogeneous condition, with a diverse presentation and multiple variables pointing to its determination, being classified as a dimensional diagnosis .In order to investigate this heterogeneity, van Hulst et al.  investigFair et al.  also evaSimilarly, the CPT, more specifically Conners’ Continuous Performance test (CCPT-II) , was useIndeed, the CPT is a common and reliable neuropsychological instrument for the evaluation of sustained attention and other attention subcomponents . AttentiDiffusion tensor imaging (DTI) seems to be a very promising method of investigating white matter microstructural abnormalities that could underpin mechanisms of inattention as it allows a shift in perspective in the investigation of the pathophysiology of ADHD, with less focus on brain regions and more emphasis on brain network organization .The sensitivity of DTI – and of its measurements, such as fractional anisotropy (FA) – in identifying microstructural tissue characteristics makes this technique a powerful and sensitive instrument to investigate changes in white matter microstructure in clinical conditions such as ADHD ,11. FA rPrevious studies have found that individuals with ADHD present either higher or lower FA values, indicating fiber abnormalities that might negatively impact their cognitive functioning ,13. As pWe believed that if these same subjects were analyzed through a dimensional analysis, considering their cognitive profile rather than their original diagnosis, the results in respect to underlying white matter measurements could be different. Thus, we aimed to investigate attentional patterns among the ADHD-I and TD children in order to identify more homogeneous groups in regard to attentional performance through an LCA. Moreover, based on the identified groups, we intended to investigate possible differences regarding underlying brain characteristics, as recommended by Fair et al. .To the best of our knowledge, very few studies have compared and analyzed the relationship between behavioral or emotional measures and physiological or neuroimaging data through a dimensional analysis in respect to ADHD ,15. The We hypothesized that individuals would be rearranged regarding attentional functioning patterns and that the new groups would be associated to differences in the FA measure of their brain tracts. Attentional performance, measured by some indexes of the CCPT-II, digit span test, and by behavioral measures, was established as an independent variable, while FA values were considered dependent variables.Recruited participants included 29 ADHD-I (ADHD of inattentive type) children aged 7–15 years and 29 TD children matched by age, sex, and type of high school attended (public or private), recruited using a purposive sampling method. ADHD-I patients were referred from public and private centers, where they had been diagnosed by an expert ADHD clinician based on the best estimate diagnostic procedure. A clinical examination, personal interview, family history from family informants, and the DSM-IV criteria were considered, as well as the results from a neuropsychological assessment, which was also part of the diagnosis protocol of these centers. ADHD participants, at the time of diagnosis, presented six or more inattention symptoms, and up to five hyperactivity/impulsivity symptoms, characterizing the predominantly inattentive type. All of the TD children were recruited from the community.Eligibility criteria were an estimated intelligence quotient (IQ) of at least 85 on the Wechsler Intelligence Scale for Children, third edition (WISC-III) , measureThree of the ADHD-I children had been taking methylphenidate for a few months, but stopped the medication at least 24 hours before testing. This research was approved by the Ethics Committee of the Universidade Federal de São Paulo and was carried out in accordance with the ethical standards as laid down in the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards. The parents provided written informed consent for all of the participants. The children provided verbal or written informed assent.Participants were submitted to a broad neuropsychological evaluation, which included an examination of the subject's intellectual level, a computerized attention test, a working memory test, and other tests to assess other cognitive functions not analyzed in this study, such as visual constructive functions, visual memory, verbal fluency, decision making, and academic performance. This evaluation was used to better delineate their cognitive profile and to identify other diagnostic conditions, such as dyslexia.As measures of interest, variables extracted from a computerized attention test – CCPT-II  – and frFive CCPT-II measures were selected following a non-structured review of CCPT studies with ADHD participants, as they were found to be very sensitive in identifying nuances in attentional profiles . The indBackward digit span test from the WISC-III  was applAttention Problems subscale and the Emotional Self-Regulation Index  of the C2, thickness=4 mm with space gap between slices =0.8 mm, yielding 30 slices) was acquired using a 3.0 -T, 43 mT/m gradient MR system  for all subjects. All images had their quality verified, rated based on an initial visual inspection, and followed by the inspection and detection of artifacts such as geometrical distortions and susceptibility effects, such as motion.A 2-D MR-DTI sequence  extraction, using R project 3.0.3. The extraction of the tracts was based on the 20 tracts of the Johns Hopkins University DTI white-matter tractography atlas , resultit-test and chi-squared test . Raw neuropsychological measures were standardized into z-score measures, adopting Brazilian norms  for a complex set of empirically observed continuous data. Categorical latent variables are not directly observed and are defined as those in which qualitative differences exist between groups of people or objects . Three dvs private], gender, and age), as possible predictors of latent classes via the three-step approach, developed by Vermunt , Bayesian information criterion (BIC), sample size-adjusted BIC (ssaBIC), Vuong-Lo-Mendell-Rubin (VLMR) test (using TECH 11 in Mplus) and the parametric bootstrapped likelihood ratio test (using TECH 14 in Mplus). The last two tests compared the fit of the model with the currently chosen number of classes (K) to the fit of a model with K-1 classes. Additionally, the quality of individual items (variable-specific entropy contribution) was calculated . Converg Vermunt , and entThe best solution found was used to predict the 20 FA mean values, via Lanza's method , which wt(55)=–2,47; P=0.02), but mean IQs were above average score of IQ scale for both groups .The TD and ADHD-I groups did not differ significantly regarding age, gender, or type of school attended . The TD The whole sample (n=58) was submitted to LCA, regardless of the origin group, in order to identify subsets of individuals with more similar attentional patterns. Three different models were built, each one comprising six continuously observed performance variables. Model 1 comprised three CCPT-II indexes , backward digit span, the attention problems subscale and emotional self-regulation index from the CBCL, balancing cognitive measures extracted from different tasks, and a behavioral variable. Model 2 consisted of four CCPT-II indexes  and the two CBCL behavioral measures, associating only CCPT-II variables with behavioral indicators. Finally, Model 3 was composed exclusively of direct attentional variables, namely the five cognitive ones extracted using CCPT-II  and a behavioral measure related to attention performance in daily situations . The fit indices for the three models and the class solutions are shown in Model 3, with a three- and a two-class solution, presented the lowest AIC, BIC, and ssaBIC. The three-class solution was not a suitable distribution for the current study due to the small number of participants in one of the classes (n=5), which would not allow the white matter analysis to be carried out appropriately. Therefore, the Model 3/two-class solution was selected as the most appropriate to reorganize the subjects according to their attentional profiles.t(56)=0.89, P=0.14), gender (χ2(1)=0.02, P=0.89), or estimated IQ (t(55)=-1.68, P=0.10), avoiding the possibility of attentional differences being due to IQ differences (see more details in Supplementary Table S1). About 36.6% of the ADHD-I individuals showed probability to be classified as belonging to the ND-class.This model/class solution comprised two groups, which were called: the ultra-high risk for attentional problems group (HR-class) , shown in Similarly, responses to the CBCL attention problem subscale revealed a score suggestive of an absence of attentional problems for the ND-class , while they were suggestive of attentional problems at a clinical level for the HR-class .Moreover, in the latent classes, in regard to the severity of the symptoms of inattention and hyperactivity/impulsivity of the subjects of each class , it was noted that 77% of those in the HR-class presented 6 or more symptoms of inattention at considerable levels (quite a bit or very much), according to responses given on the SNAP scale. Approximately 32% of those in the ND-class also presented 6 or more symptoms of inattention at the same levels. Thus, although there was a predominance of symptoms of inattention among the HR-class, these symptoms were also observed at significant levels among the ND-class.In respect to comorbidities, before the LCA analysis, four ADHD participants presented dyslexia and one anxiety disorder. No comorbidities were found among the TD subjects. After the LCA division, two of the participants with dyslexia and the one with anxiety were placed in the HR-class. The remaining dyslexic patients were placed in the ND-class. Only one of these latter participants had his neuroimaging excluded due to poor quality.All six continuous indicators of Model 3  were compared regarding their capacity to discriminate the new subgroups. The indicator with the highest entropy was the CCPT-II omission index (entropy=0.674), being the one with the best discriminating ability for both classes. The Hit RT Block Change indicator had the lowest entropy (entropy=0.199), thus with the lowest power to discriminate groups. The other indexes presented the following entropy contributions: Variability=0.622; Hit RT ISI=0.52; CBCL attention problems=0.481; Hit RT=0.414.A regression analysis was performed to identify if some variables could be powerful predictors of classes in Model 3. Age, gender, type of school, and a clinical diagnosis of ADHD were used in this analysis. Only a clinical diagnosis of ADHD was found to be a strong predictor of the HR-class, , providing convergent evidence for predicting the classes. The other variables - age , gender , and type of school  - were not statistically significant, revealing divergent validity.After the sample was best rearranged into two new classes according to their attentional functioning, DTI images of these individuals were analyzed in order to explore possible neurobiological differences between the classes.t(40)=0.18, P=0.85), gender (χ2(1)=0.06, P=0.81), or IQ (t(40)=–1.97, P=0.06), and, therefore, did not interfere with the analysis of the DTI images (see more details in Supplementary Table S2).Only 42 of the 58 subjects had their DTI images considered due to quality criteria. These 42 individuals, when compared respecting the new classes, did not differ significantly regarding age , but when subjects were reclassified according to cognitive and behavioral variables, only 33.1% of the entire sample were classified as part of the class with an ultra-high risk of attentional problems (HR).Each class comprised individuals with more similar attentional profiles. Some of the constructs, such as Omissions, Variability, and Hit RT ISI, proved to be more sensitive than others in discriminating the classes. According to a meta-analysis of many versions of the CPT paradigm, omission errors are one of the most consistently impaired measures among individuals with attentional deficits . VariabiAlthough the classes differed in respect to their attentional profiles, it is noticeable that the ND-class performed better in all measures considered. This effect could pose some questions about the rearranging criteria of the classes. At first sight, it could seem that participants were clustered according to symptom severity. However, considering that about 36.6% of ADHD-I individuals showed a higher probability to be classified as belonging to the ND-class, we assumed that the two-class solution allowed the identification of different attentional profiles among ADHD-I subjects. Moreover, approximately 32% of the ND-class presented 6 or more inattention symptoms according to SNAP-IV, which suggested that although they had some inattentive symptoms, they had a normal attentional profile according to the measures considered here. Thus, ADHD individuals clustered in different classes may have differed in respect to their deficit patterns (in some domains and not in others) and not necessarily in respect to their deficit severity. Indeed, ADHD individuals can present typical performance even in measures that are commonly impaired in the disorder . Peterson et al.  pointed The IFOF connects the dorsal, medial occipital, and parietal regions with the caudodorsal prefrontal cortex . The IFOThe ILF is a ventral associative bundle with long and short fibers connecting the occipital and temporal lobes . The lefWe can, therefore, hypothesize that if the right hemisphere fiber tracts responsible for attention control and visual-spatial processing are not functioning properly in the HR-class, the left hemisphere tracts – IFOF and ILF – may have partially assumed their processing through compensatory mechanisms. This rearrangement may have led to increased axonal packing of these left hemisphere fibers, and, thus, help to explain the higher FA mean values for IFOF and ILF fibers in the HR-class.vs TD). Contrasting with the current results, in the previous study no significant differences were found between the groups. Thus, through this classical categorical approach, no white matter differences between the groups were found, even after having selected ADHD individuals with the same subtype, which would allow a greater uniformity within the groups (see reference 14 for more details). However, when a more refined analysis of the possible pathophysiological mechanisms of dysfunction was carried out, arranging participants according to observable cognitive and behavioral measures, neurobiological differences were found.Considering the cognitive and behavioral profiles of individuals as the starting point and relating them to white matter abnormalities seemed to be a more sensitive approach to understand anatomo-functional relationships. As mentioned before, a previous analysis conducted with the same sample of the current study  comparedThe differences between the findings of the dimensional (current) analysis and the categorical (previous) analysis gave further support to the idea that brain-behavior relationships may not respect the arbitrary limits imposed by diagnostic classifications, and seemed to vary in accordance with homogenous phenotypes.Although the present study restricted the sample diversity, comprising only ADHD-I and control individuals, the findings indicated the existence of distinct neuropsychological patterns among the participants, consonant with the conclusions of Fair et al.  and van The limitations of this study involve the use of cognitive variables extracted from one attentional task only. As no more indexes could be added to the LCA due to the size of the sample, the replication of the current analysis with a larger sample would allow more cognitive and behavioral indicators to be included. A larger sample would probably permit participants to be regrouped in more classes, and, therefore, allow the identification of a greater diversity of attention profiles among subjects. The small size of our sample also restricts the generalization of our findings.Our results do not negate the clinical need for diagnostic categories or the existence of the categories themselves but highlight how the heterogeneity of a disorder reflects the need to produce evidence based on cognitive, behavioral, brain, and genetic features. The newly established sub-groups can respond differently to specific interventions and, in the long term, efforts to identify groups of individuals with more homogenous characteristics may be helpful in their treatment and management.pdf].Click here to view [


N = 1092 pairs) on lack of dispositional mindfulness [Mindful Attention Awareness Scale (MAAS)], ADHD traits [Conners’ Parent Rating Scale-Revised (CPRS-R): inattentive (INATT) and hyperactivity/impulsivity (HYP/IMP) symptom dimensions] and life satisfaction . Twin model fitting analyses were conducted. Phenotypic correlations (rp) between MAAS and CPRS-R  were small, but significant and largely explained by shared genes for INATT  and HYP/IMP  with no significant contribution of environmental factors. MAAS, INATT and HYP/IMP significantly and independently predicted life satisfaction. Lack of dispositional mindfulness, assessed as self-reported perceived lapses of attention (MAAS), taps into an aspect of attentional functioning that is phenotypically and genetically distinct from parent-rated ADHD traits. The clinically relevant incremental validity of both scales implicates that MAAS could be used to explore the underlying mechanisms of an aspect of attentional functioning that uniquely affects life satisfaction and is not captured by DSM-based ADHD scales. Further future research could identify if lack of dispositional mindfulness and high ADHD traits can be targeted by different therapeutic approaches resulting in different effects on life satisfaction.To get additional insight into the phenotype of attentional problems, we examined to what extent genetic and environmental factors explain covariation between lack of dispositional mindfulness and attention-deficit/hyperactivity disorder (ADHD) traits in youth, and explored the incremental validity of these constructs in predicting life satisfaction. We used data from a UK population-representative sample of adolescent twins (The online version of this article (10.1007/s00787-019-01279-8) contains supplementary material, which is available to authorized users. Mindfulness has been defined as the self-regulation of attention towards the present moment and the orientation to one’s experience with an attitude of curiosity, openness and acceptance . Self-reDispositional mindfulness refers to mindfulness as a psychological trait independent of mindfulness acquired as a skill through training and practice, such as meditation. This means that dispositional mindfulness can be assessed in meditation-naïve individuals, but dispositional mindfulness can also increase following mindfulness training and practice , 9. The acting-with-awareness, which is closely related to MAAS [acting-with-awareness subscale of the five facet mindfulness questionnaire (FFMQ) [observing, describing, non-judging and non-reacting) showed small or non-significant associations with ADHD outcomes in college students, of whom half had ADHD [There is increasing evidence that the lack of dispositional mindfulness is associated with ADHD. Higher scores on dimensional assessments of ADHD traits have been associated with the lack of dispositional mindfulness (MAAS) both in university students with and without ADHD , as well to MAAS . Similare (FFMQ) , comprishad ADHD  and in ahad ADHD . Thus, pThe negative association between ADHD and the attentional aspect of dispositional mindfulness may arise from aetiological overlap in the constructs to assess ADHD symptoms/traits and (a lack of) dispositional mindfulness. Both traits are heritable: a lack of dispositional mindfulness (MAAS) around 30%  and ADHDA way to explore the relevance of studying similarities and differences between these two associated concepts is to look at their incremental validity in predicting a clinically relevant outcome. ADHD traits are a description of observed behavioural inattention, hyperactivity and impulsivity, which is conceptually different from MAAS that captures perceived lapses of attention. Both ADHD traits and MAAS can predict aspects of well-being , 26. In N = 1092). We expect a greater shared genetic rather than environmental influence in explaining the association between the constructs. We assess the lack of dispositional mindfulness by an abbreviated 5-item version of MAAS [The purpose of the present study is to examine associations between two possibly complementary attentional constructs: a lack of dispositional mindfulness and ADHD traits, in a UK population-representative sample of adolescent twins . ADHD t of MAAS , 28. We  of MAAS , 30. The of MAAS .The aims of the study are, first, to examine phenotypic associations between a lack of dispositional mindfulness and ADHD traits, separately for inattentiveness and hyperactivity/impulsivity. Second, we aim to investigate the extent to which shared genetic and environmental factors explain the associations between these traits. Third, we intend to explore the incremental validity of the lack of dispositional mindfulness and ADHD traits, through studying their unique contributions to predict life satisfaction as a clinically relevant outcome.N = 1092 monozygotic (MZ) and dizygotic (DZ) twin pairs : 418 MZ  and 674 DZ .Data came from the 16-year assessment wave of the UK population-representative Twins Early Development Study (TEDS) , which cα = 0.76) to excellent (α = 0.91) for all scales (Online Resource 2).In the current study, Cronbach’s alpha internal consistency was acceptable  [The lack of dispositional mindfulness was assessed using an abbreviated version of MAAS, comprised of five items shown to have the highest differential item functioning , 33. The2, 0.94)  with the2, 0.94) . The adoADHD traits were assessed using parent ratings on the DSM-IV-based ADHD subscales of the Revised Conners’ Parent Rating Scale (CPRS-R) , which cLife satisfaction, as a primary component of subjective well-being , was assh2 or A), shared environmental (C), and non-shared environmental (E) influences on a trait or the covariation between traits. E includes measurement error.Analyses were based on the Twin Method , which arp) between MAAS and ADHD traits (INATT and HYP/IMP separately) (aim 1) and to study genetic and environmental aetiologies of these associations (aim 2), structural equation twin model fitting was conducted in M× [rMZ and rDZ are the correlations within, respectively, MZ and DZ pairs for one trait . To obtain CTCT correlations, one trait  in twin 1 is correlated with another trait  in the co-twin. Twin and CTCT correlations allow a first impression of the extent to which individual differences (variance) in variables, and their associations (covariation), are attributable to genetic (A) and environmental (C and E) factors.To study phenotypic (observed) associations  between MAAS and CPRS-R dimensions. These correlations can range from − 1 to 1, and indicate the extent of genetic and environmental sharing between two traits.Next, these impressions were confirmed by fitting a Cholesky decomposition, represented as a correlated factors solution Fig. , which frp between MAAS and INATT due to A, can be estimated as rA × √a11 × √a22 divided by rp. Previous studies using the current sample [We also estimated the proportion of the phenotypic correlations attributable to genes or environments. For example, from Fig. t sample  revealedThe Conners’ scales were positively skewed and transformed using a Van der Waerden transformation . FollowiR2) from step 1 to step 2 in the dependent variable (life satisfaction) not accounted for by ADHD traits and vice versa.To address the incremental validity of MAAS and ADHD traits (aim 3), regression analyses were conducted using Stata . The ‘clThe descriptive statistics for all measures are presented in the Online Resource 2.rp= 0.18, 95% CI 0.13–0.22) and HYP/IMP , with the lack of dispositional mindfulness reflecting higher ADHD traits  and non-shared environmental (E) influences on MAAS, INATT and HYP/IMP. For MAAS, the DZ correlation was slightly less than half the MZ correlation, suggesting the absence of shared environmental effects , and that heritability should be interpreted as both additive  and dominant  genetic effects. For ADHD dimensions, DZ twin correlations were greater than half the MZ correlations (Table C).The MZ twin correlations were larger than the DZ correlations, but less than one Table , indicatns Table , indicatA) in association between MAAS and ADHD dimensions. The MZ CTCT correlations  were similar in magnitude to the phenotypic correlations  (Table E) played only a small role in explaining association between MAAS and ADHD traits. DZ CTCT correlations  were roughly half the respective MZ CTCT correlations, suggesting shared environmental (C) influences play no or little role in association between MAAS and ADHD traits.The MZ CTCT correlations were larger than the DZ CTCT correlations Table , suggestχ2 (df = 111) = 189.78, p < 0.001, AIC = − 32.22, BIC = − 293.37. As dropping parameters can artificially inflate non-significant estimates, results from the full ACE model are presented. Significant heritability was found for MAAS (A= 35%), INATT (A= 61%) and HYP/IMP (A= 65%)  and due to both shared and non-shared environmental influences for INATT  and HYP/IMP  (Table rA= 0.37 for INATT and rA= 0.21 for HYP/IMP)  and HYP/IMP  (Table χ2 (df = 3) = 0.00, p = 1.00.The ACE model was a good fit to the data as indicated by the negative AIC and BIC values: MAAS was a significant and negative predictor of life satisfaction beyond INATT and HYP/IMP and vice versa Table , providiThis is the first report on the genetic and environmental aetiologies of phenotypic associations between a lack of dispositional mindfulness and the INATT and HYP/IMP dimensions of ADHD traits, allowing to explore the complementary value of these two attentional constructs in an adolescent population. We also explored if the lack of dispositional mindfulness and ADHD traits independently contribute to predicting life satisfaction. MAAS and ADHD trait measures showed small significant correlations, which were largely explained by shared genetic influences. However, genetic correlations between the lack of dispositional mindfulness and ADHD trait measures were modest and environmental correlations non-significant. In addition, the two attentional constructs, MAAS and CPRS-R, were unique negative predictors of life satisfaction, an important aspect of mental well-being, supporting the respective incremental validity of these questionnaires as clinically relevant outcomes.r = − 0.65, p < 0.01) [r = − 0.74, p < 0.0001) and without ADHD  [The phenotypic correlations between the lack of dispositional mindfulness and ADHD traits in our study were lower than found in the previous studies. Earlier results showed larger correlations between dispositional mindfulness as assessed by MAAS and ADHD traits in high school attendees aged 14–20 years ( < 0.01)  and in u 0.0001) . However 0.0001)  assessed 0.0001)  also use 0.0001) , 28. TheAnother finding worth noting is the absence of a significant difference between INATT and HYP/IMP in their phenotypic correlation with MAAS. Edel et al.  found MAThe results from the twin models highlight modest overlap of genetic, and no significant overlap of environmental influences. Genetic factors largely explained the phenotypic covariation between the lack of dispositional mindfulness and ADHD traits. This is in line with the “generalist genes hypothesis” , 50, staacting-with-awareness facet of KIMS [Trait-specific environmental effects indicate that the environment contributes more to differentiation among the traits rather than overlap between them. It is unknown what these influences are, but could involve differential effects of parenting, life events, divergent cultural exposure, in addition to measurement error. Reductions in ADHD traits have been found following MBIs in normally developing , 55 and  of KIMS . Therefoacting-with-awareness facet of FFMQ and decreased HYP/IMP symptoms [One proposed mechanism linking the lack of dispositional mindfulness and ADHD traits involves regulation of mind wandering which is highly correlated with MAAS  and withsymptoms . The shaHowever, although both adolescents with a lack of dispositional mindfulness and adolescents with high levels of ADHD traits likely experience lapses of attention, the underlying aetiologies were largely independent, suggesting different mechanisms that could underlie the expression of traits captured by MAAS and measures of ADHD traits. Furthermore, MAAS and ADHD traits were unique negative predictors of life satisfaction, replicating the findings of Black et al. , and extrp = 0.18, HYP/IMP: rp = 0.13). In a comparable twin study with 2369 adolescents aged 16–17 years and 1067 parents, the correlation between self- and parent-rated ADHD traits was 0.37 [r = 0.34) was found in the current sample, even though the response scales were different between the informants [Strengths of the current study are the use of a large population-representative sample of twins allowing genetically informative analyses, and the use of a parent- rather than self-report measure of ADHD traits. In addition, because MAAS is self-report and ADHD traits were assessed with parent report, the current phenotypic correlations are not simply a result of shared rater variance. However, the use of different informants comes with limitations as well. The low correlations and incremental validity might be a result of informant discrepancies rather than an actual difference between the constructs. Nevertheless, in previous studies, substantially higher correlations were found between ADHD ratings by different informants compared to the phenotypic correlations found in the current study  . The impThe present study used an abbreviated 5-item version of MAAS, which is considered as useful as the original 15-item MAAS , and hasSupplementary material 1 (DOCX 22 kb)Below is the link to the electronic supplementary material.