Upon 808 nm irradiation, the high photothermal conversion efficiency and on‐demand NO release are realized simultaneously. Due to the unique properties of NO, enhanced antitumor efficacy of mild PTT based on BNN‐Bi2S3 nanocomposites is achieved in vitro and in vivo. Mechanism studies reveal that the exogenous NO from BNN‐Bi2S3 could not only impair the autophagic self‐repairing ability of tumor cells in situ, but also diffuse to the surrounding cells to enhance the therapeutic effect. This work points out a strategy to overcome the difficulties in mild PTT, and has potentials for further exploitation of NO‐sensitized synergistic cancer therapy.Mild photothermal therapy (PTT), as a new anticancer therapeutic strategy, faces big challenges of limited therapeutic accuracy and side‐effects due to uneven heat distribution. Here, near infrared triggered nitric oxide (NO) release nanocomposites based on bismuth sulfide (Bi Photothermal therapy (PTT), which converts light energy into heat through light‐absorbing molecules or nanoparticles, has drawn considerable attention in recent years.2S), have good diffusion ability in tumor tissue due to their unique chemical properties.To improve therapeutic efficacy, one possible approach is to combine mild PTT with other treatment modalities.Since NO participates in various kinds of physiological activities, construction of the targeted delivery system instead of the existing sustained‐release NO donor is extremely valuable.2S3) nanoparticles and hydrophobic NO donor, N,N′‐Di‐sec‐butyl‐N,N′‐dinitroso‐1,4‐phenylenediamine (BNN), which was loaded on the surface of Bi2S3 nanoparticles . Then, BNN was loaded through hydrophobic–hydrophobic interaction. The UV–vis absorption spectra, Fourier transform infrared (FT‐IR) spectra, and thermal gravity analysis (TGA) verified the successful loading of BNN on the surface of Bi2S3 nanorods . The above data suggested that BNN‐Bi2S3 nanocomposites were suitable candidates for biological applications.The structure of BNN‐Bi2S3 was investigated. First of all, the temperature of BNN‐Bi2S3 aqueous solution was recorded upon NIR irradiation while PBS was set as control . This high photothermal conversion efficiency was the foundation to provide enough energy for the following decomposition of NO donors. As shown in Figure 2S3 under NIR irradiation (1.0 W cm−2) could reach nearly 10 × 10−6m after 15 min. Compared to the other NIR‐triggered NO releasing nanomaterials, this NO delivery and release system exhibited better NO release efficiency . As mentioned earlier, the reasonable surface modification by the amphiphilic Tween‐20 provided enough storage space for the organic NO donors, ensuring the efficient NO delivery. More importantly, the high photothermal conversion efficiency of Bi2S3 nanocomposites provided enough energy for BNN decomposition. These two aspects are the key characters in the BNN‐Bi2S3 nanocomposites as well as in other controllable NO delivery materials.Due to its broad absorption in NIR region, the NIR‐triggered NO release property of BNN‐Bil Figure e. The ph−2  NO could release efficiently under the mild condition with minimal heat damage to normal tissues; ii) only local heat could cause NO release, which avoided the undesired NO release to minimize the side‐effects of NO. The stability of the as‐prepared BNN‐Bi2S3 nanocomposites was tested in physiological condition. The result showed little NO release after stirring for 24 h . Therefore, utilizing this high local temperature strategy could help to develop a real on‐demand NO release system, and further potentially promote the development of the general drug delivery system in biomedical field.Next, we monitored the temperature throughout the NO release process using an infrared thermal imager. The temperature of the samples kept no more than 46 °C under NIR irradiation at 1.0 W cm2S3 and BNN‐Bi2S3 were evaluated on the three kinds of human cells. The results showed that neither Bi2S3 nor BNN‐Bi2S3 has obvious cytotoxicity . Furthermore, intracellular distribution of BNN‐Bi2S3 was visualized through dark‐field imaging, and then quantified through inductively coupled plasma mass spectrometry . Herein, the intracellular NO release property of BNN‐Bi2S3 was evaluated using fluorescent probe (DAF‐FM DA). Both of the fluorescence images and flow cytometry results demonstrated that only the cells treated with BNN‐Bi2S3 and exposed to NIR irradiation showed obvious green fluorescence in the cytoplasm, successfully confirming the efficient generation of NO in cells . More importantly, the NO signal could be observed not only in the irradiated cells but also in the unirradiated cells out of laser spot, indicating the high diffusivity of NO among cells .The biocompatibility and membrane‐permeability are both important for NO delivery system. At the beginning, the cytotoxicity of BiFigure2S3 nanoparticles for 24 h. After incubating, the frozen sections of the MCTS were prepared. The distribution of BNN‐Bi2S3 nanoparticles was observed using dark‐field microscope. It is obvious that the signal of BNN‐Bi2S3 nanoparticles could either appear on the periphery of the MCTS or the interior surface of some porous channels  based on BEL‐7402 cells was established in this work. As shown in 2S3 nanocomposites were examined on BEL‐7402 cell lines in vitro. The cell viability decreased obviously with the increase of the concentration and NIR power density . Besides, Acridine Orange (AO) was also used for autophagy detection, which showed a characteristic increase in red fluorescence that indicated the appearance of acidified autophagosome  or inhibitor 3‐methyladenine (3‐MA) during PTT and made a comparison with Bi2S3 or BNN‐Bi2S3 under NIR irradiation. The cell viability results demonstrated that Rapa could reduce the therapeutic effect of PTT. On the contrary, when autophagy was inhibited by 3‐MA, the cell viability decreased to the same level as the cells treated with BNN‐Bi2S3 under NIR irradiation . Taken together, we could draw a primary conclusion that autophagy might protect the cell death in mild PTT, while NO functioned to prevent this protective effect and aggravate the heat‐induced injury.Next, the molecular mechanism was investigated. It is generally acknowledged that the in‐depth mechanisms of NO‐associated synergistic therapy should be investigated by using molecular and genetic methodologies.I Figure c. The co2S3 under NIR irradiation, indicating the complete release of cytochrome c from mitochondria into cytosol. The released cytochrome c would further activate the caspase‐3 mediated apoptosis pathway  Bi2S3 + laser; v) BNN‐Bi2S3 injection; vi) BNN‐Bi2S3 + laser. The dose of injected Bi2S3 or BNN‐Bi2S3 was 20 mg kg−1, and the NIR exposed time was 10 min (0.35 W cm−2). The temperature of the exposed area was recorded using an infrared thermal imager during the PTT process. The tumor temperature of the groups iv) and vi) increased to 46 °C under NIR irradiation while the tumor temperature of the groups ii) only increased a little  and multispectral optoacoustic tomography (MSOT) after intratumor injection . The heterogeneous distribution of Bi2S3 nanoparticles would cause heterogeneous distribution of heat in tumor site, which might result in unsatisfied therapeutic effect. On the contrary, although the distribution of BNN‐Bi2S3 nanocomposites in tumor was still heterogeneous, the well‐diffused NO could distribute uniformly in the whole tumor to synergistically treat tumor through inhibiting the autophagic self‐repairing process. Thus, using BNN‐Bi2S3 nanocomposites as the PTT agents could remarkably increase the therapeutic effect. The pathological sections of all the tumor tissues were further investigated. Hematoxylin and eosin (H&E) staining and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining showed that mild PTT inhibited tumor growth in comparison with the control group, and the synergy of NO and mild PTT enhanced the inhibition effect  PBS injection; ii) laser; iii) Bi0 min 0.3 W cm−2. 0 min 0.3 W cm−2. 0 min 0.3 W cm−2. 0 min 0.3 W cm−2. 0 min 0.3 W cm−2. 2S3 nanoparticles with the thermally decomposition ability of NO donor, BNN‐Bi2S3 nanocomposites could act as both photothermal agent for PTT and drug carrier for NIR triggered NO release. The NIR light generated NO could diffuse homogeneously in solid tumor to impair the self‐repairing ability of tumor cells in mild PTT. As a result, BNN‐Bi2S3 nanocomposites exhibited more effective tumor inhibition ability than Bi2S3 alone both in vitro and in vivo. In a word, the newly‐prepared nanocomposites could simultaneously realize a controllable NO release and PTT, and the mechanism of their synergistic effects in cancer therapy was also illustrated. Consequently, these features endow BNN‐Bi2S3 nanocomposites with potentials for further exploitation as a powerful platform for NO‐sensitized synergistic antitumor therapy.In conclusion, a new therapeutic strategy based on the well‐designed nanocomposites containing photothermal conversion nanoparticles and NO donors was established. Combined the photothermal conversion effect of BiThe authors declare no conflict of interest.SupplementaryClick here for additional data file.


ADHD (attention-deficit/hyperactivity disorder) is gradually being acknowledged as a functionally impairing disorder across the lifespan, underscored by heritability. Nonetheless, lack of ADHD (adult attention-deficit/hyperactivity disorder) data from South Africa is alarming which could be due to either the unawareness of ADHD symptoms or underutilisation of available screening measures. Undiagnosed ADHD may influence family- and working lives unpleasantly. Parenting a child with ADHD may intensify parental stress through functional impairment notwithstanding the diagnosis of ADHD.Eighty-one biological parents of children diagnosed with attention-deficit/hyperactivity disorder were screened using self-reporting measurements. ADHD self-report scale (ASRS-V 1.1) identified either positive or negative subgroups; the Weiss functional impairment rating scale (WFIR-S) for functional impairment and the Jerome driving questionnaire (JDQ) for risk-taking behaviour specifically driving.Of the 39 (48%) parents who experienced impairment in all seven areas of functioning, 23 (59%) screened negative for ADHD, while 16 (41%) screened positive. A significant association was found between parents who screened either positive or negative for ADHD and functional impairment across five of the seven individual categories namely family, work, self-concept, life-skills and social functioning.This study emphasised the high incidence of functional impairment in parents of ADHD children. Although a substantial number of parents screened negative for ADHD, they still reported impairment in functioning; probably due to undiagnosed ADHD with comorbid psychiatric disorders, and/or parental stress due to the complex behaviour of the child. Parents of children diagnosed with ADHD should be screened for functional impairment followed by referral for psychiatric assessment and parent management training to achieve better clinical outcomes. This study was motivated by a lack of prevalence data from the South African context on parental functional impairment with regard to parental ADHD and the incapacitating effects of having to raise a child with ADHD.1 A Danish study has revealed a causal association between poor child health and parental outcomes, focussing on CADHD (child attention-deficit/hyperactivity disorder) and ADHD.1 Empirical studies showed that parents of children with learning or behavioural problems such as those in ADHD, experience higher levels of stress than other parents.2Research on how raising a child with ADHD affects the functioning of parents, has received little attention.3 Early identification of potential at-risk parents is necessary so that interventions aimed at reducing the stress in the child-parent systems can be implemented to reduce future behavioural and emotional problems for both parent and child.1Parental stress developing from parenting an ADHD child is a complex construct involving behavioural, cognitive, and affective components that could manifest in a strained parent-child relationship.4 Studies showed that ADHD persists during adolescence and into adulthood in around 67% of individuals either as ADHD or in ‘partial remission’ .4 Neuropsychological and neuroimaging studies, genetics, persistent and co-morbid psychiatric disorders in adults, response to treatment, and follow up studies of ADHD children to adulthood, support this trend in validating adult ADHD.5 In recent international studies, the prevalence of ADHD was in the range of 2%–5%.6 Persistent forms of ADHD have a higher familial loading than non-persistent types.7Descriptions of ADHD appeared in the psychiatric literature from 1976.4 Identified genetic associations for heritability in ADHD are close to 76%.8 A survey has shown that lower income countries report a lower prevalence (1.9%) than higher income countries (4.2%).9There is growing recognition of the importance of ADHD in the parents of children with ADHD, as close to 20% of parents will have ADHD themselves.10 They found a prevalence rate of 36.4% of ADHD symptoms in parents of ADHD children with an increase in substance abuse, unemployment, depressive and bipolar disorders.In a recent South African study, Mohammedy et al. studied the persistence of symptoms of CADHD into adulthood.11 The results of this study underscored the immense stress and impairment these families dealt with. An increase in the severity of ADHD symptoms was directly associated with higher levels of family dysfunction, even after controlling for comorbid disorders with lower levels of social support and quality of life.12Cheesman explored parenting stress levels in parents raising ADHD children.5In addition, professional ignorance of ADHD has far-reaching consequences for ADHD parents, namely poverty, limited education, less professional employment, more frequent changes in employment, poor work performance, higher rates of quitting or fired from jobs. Barkley et al. found elevated rates of speeding citations, suspended licenses and crashes with or without bodily injury in ADHD.4 These changes mean that many people who previously met the ‘in partial remission criteria’ will meet full criteria for ADHD under the DSM-V.13 Adults often underreport their symptoms, perhaps considered them as part of their personality rather than abnormal.9DSM-5 recognises that impairment from the symptoms of ADHD may develop later in life and sometimes appear by early adolescence-by age of 12 years. The reduction in the symptom threshold for adults as compared to children recognises the age-dependent changes where there is clear evidence of functional impairment with or without symptoms of ADHD.12Parenting an ADHD child with the parent possibly having ADHD is a relatively new and challenging area of research, given the high heritability and comorbidity of ADHD.We hypothesized that the biological parents of ADHD children would show a similar clinical picture as their child; adult functional impairments and risk taking behaviours could be associated with symptoms of ADHD and/or high stress levels from parenting a child with ADHD.13This study focussed on functional impairment, risk-taking behaviour related to driving, and to screen for negative or positive ADHD .The protocol was approved by the Faculty of Health Sciences Research Ethics Committee of the University of Pretoria.A sample of eighty-one parents of previously diagnosed ADHD children was screened  who had neither a self-referral nor a self-report of an ADHD diagnosis before. Screening took place at the Weskoppies Adolescent and Child Psychiatric Out-patient Unit.Informed consent was obtained from the participants. Three sets of self-reporting questionnaires were handed out to the identified parents for completion. All participants were literate and fluent in English.14 (ASRS – V1.1) was used to screen for core symptoms of ADHD. If part A has four or more responses, then it was considered as more predictive of a definitive diagnosis of ADHD. An adaptation of the Weiss Functional Impairment Rating Scale–Self-report (WFIRS – S)14was used to assess functional impairment in the family, work, school, life skills, self-concept, social aspects and risk. The Weiss functional impairment rating scale (WFIRS-S) was scored by the average of the total number of items per category. When defining impairment for clinical purposes, clinicians consider any category with a mean score ≥ 1.5 as impaired.14 An adaptation of the Jerome driving questionnaire (JDQ)15 was used as a self-reporting instrument of which only part B was used for the purposes of the study. The JDQ provided a subjective account of driving style  on a scale from zero to ten.15The Adult Self-report ScaleThe focus of the analysis was a comparison of respondents who screened positive and negative for ADHD, based on the ASRS-V1.1 instrument. Univariate statistics were reported. Due to a large number of missing values, resulting in relatively small sub-sample sizes when the data set was split, nonparametric tests were performed. Fisher’s exact test (reported with the Chi-square test results) were used to assess the relationship between parents who screened positively and negatively for ADHD and each of the functional impairment categories. Mann-Whitney’s test for two independent samples  was used to evaluate the two parent groups with respect to the four driving style elements (JDQ Part B).16Analysis was conducted using SPSS  version 22.N); parents in this study, 57 (70%) were females. The mean age for males was 42.04 (SD 5.77) and 40.33 (SD 7.61) for females. Just over half of the parents were unemployed.Of the 81  and those who screened positive for ADHD . Of the 18 (22.0%) respondents that screened positive for ADHD, 15 (83.3%) were females.According to the ASRV self-report scale response parents were classified into two groups, those who screened negative for ADHD , family (80%) and life-skills (71%) categories than in the work, social, school and risk categories. The categories within the ADHD subgroups showed that functional impairment was more evident in those parents who screened negative for ADHD than those who screened positive for ADHD with reference to categories .n = 12) and 69.2% females (n = 27) (see Approximately 50% (39) of the 81 parents (positive and negative subgroups) were impaired in all categories of which 30.8% were males ( 27) see .The findings of the WIFR-S as per the ADHD subgroups are represented in n = 18) were 100% impaired in the family and self-concept categories, whereas life-skills impairment fell short by one parent. Almost 90% (n = 16) from the positive subgroup were impaired in all seven domains, which accounted for 20% of the total parent sample, shown in Of the ADHD positive group, all parents (p < 0.1). These findings gave an indication of the extent to which the two ADHD subgroups contributed to impairment in family, work, school, social, life-skills, and self-concept and risk categories.Descriptive findings of ADHD subgroups for functional impairment and tests for significance between the two are reported in Of the 39 parent drivers who represented just under 50% with a valid driver’s licence, 6 (15%) were from the positive and 33 (85%) from the negative ADHD subgroups . On averThe average age of the parents was close to 43 years, which suggests an appropriate adult sample for this study. There was a larger imbalance in their gender groupings. This study had predominance (70%) of female parents, who represented a larger proportion for employment status. There was also a predominance of females in the ADHD subgroups with impairment in functioning. The high unemployment rate could also explain this finding.Functional impairment was positively associated with age, although the gender composition of the sample attenuated this association with females .4There were significant impairments in the following categories’ of functioning; self-concept, family, life skills, social and work categories when controlling for ADHD positive screened parents . These f11 This suggests a lack of ADHD research in Africa. Internationally, parental outcomes were by Wymbs who reported a higher divorce rate for parents of children with ADHD.1The first study in South Africa that highlighted the effect of the ADHD child on the parent and the family was completed by Cheesman.12Children with ADHD often demonstrated, oppositional-defiant behaviour and conduct problems resulting in increased levels of parental stress, low parenting self-efficacy, low parental self-esteem and guilt. No studies to date, addressed psychosocial interventions for ADHD and comorbid disorders in preschool-aged children or adults.15Disrupted parental sleep may include poorer daytime functioning, including greater daytime sleepiness, lowered frustration tolerance, impaired attention and memory. Poor sleep in the positive and negative ADHD subgroups could also be an explanation for the non-significant findings of the adapted JDQ variables independent of diagnoses in this study.17 Observing this in this study suggests a reduced prevalence of adult ADHD occurs as an underestimation of its true prevalence.Epidemiological studies tend to find subjects that are often unaware of a disorder but may be aware of impairments. Symptoms of ADHD decline with age at the same time, functional impairment and low socio-economic outcome prevalence rates increase even with a reduced number of symptoms.18Adults with ADHD have strained relationships with their children who are diagnosed with ADHD and other family members. They are often unable to be emotionally supportive, have poor listening skills, have confounding family activities and are unable to sustain routines-including treatment regimens.p = 0.016)  .p = 0.075), taking notes, completing assignments, inefficient completion of work, not working to full potential and inconsistent grades was most problematic in the parent sample (18In the school category of impairment ( t sample  Biederma4 In the work category of impairment ( p = 0.002) more females were unemployed, had problems getting work done, performing required duties, working to their potential, being late, poor performance evaluations and keeping a job . In the category of self–concept, an increased tendency ( p = 0.032) in low self-esteem, being frustrated, discouraged, not happy with life and incompetent were significant. The limited self-optimism and self–concept indicate decreased quality of life  are getting into arguments, poor participation in extra-mural activities and inappropriate talking. Due to these handicaps, a number of parents feel isolated, lonely and ashamed about failures, even in the presence of a high IQ.4 The risk behaviour category ( p = 0.084) is approaching significance on the items that were increased; smoking cigarettes, drinking alcohol and being verbally aggressive  and/or ADHD specified otherwise  as valid diagnostic groups. This supports the DSM-5 criteria that is accounting for adult symptom clusters, including delayed presentation of functional impairment. Jerome and Segal suggest driving impairment should be included in screening tools in the future for ADHD.15 and non-parametric tests.The small study of 81 has lowered the power of the tests to detect statistically significant effects and theta would have shown up in a bigger sample. However, the limitations of the small subsample sizes were reduced and the overall representation of the parent samples were improved by using validated scales22 Our study had few valid drivers and the findings were alarming as older drivers showed impaired driving skills and behaviours. More studies are needed as ADHD and driving has medico-legal implications and applications for the general psychiatrist.Research on driving skills on its own and ADHD is practically absent in South Africa. South Africa has one of the highest motor vehicle accident rates in the world.This study contributes to the literature on ADHD and the parent/s living with an ADHD child. In keeping with other studies on ADHD, the findings suggest that there are a large number of undiagnosed adults with ADHD even in a South African context associated with significant impairment in functioning.It is evident that the age of onset criteria for ADHD is less reliable and important than the persistence of symptoms and functional impairments of ADHD across the lifespan.These findings suggested that a significant number of parents who screened negative for ADHD and were parenting an ADHD child, may have experienced parental stress or could suffer from undiagnosed ADHD with comorbidities, as reflected by reporting impairment in functioning.This study reflected a strong association between poor child mental health (CADHD) and parent outcome. All mental health care workers should be cognisant of impaired clinical functioning in these vulnerable parents, which might indicate undiagnosed ADHD especially in those having a strong familial history of ADHD and parental stress. To achieve better clinical outcomes in these susceptible parent-child systems, parents should be promptly referred for further psychiatric assessment as well as parent management training.13 Future research should embark on case controlled longitudinal studies including follow-up studies in treated cohorts.Future development should include the integration of DSM-V and the JDQ to develop and validate new appropriate screening tools for adults to identify on-going life difficulties in these vulnerable adults for ADHD and poor functioning.


Bartonella spp. are opportunistic bacterial pathogens, which are transmitted by a large variety of arthropods. The aim of this study was to investigate the presence and host-associations of these Gram-negative bacteria in heart tissues of bats collected in four different countries from eastern and central Europe and to analyze their phylogenetic relationship with other bat-associated bartonellae.Bats are among the most widely distributed mammals worldwide and can represent hosts or reservoirs for a number of different pathogens. Bartonella spp. DNA in heart tissues of bats from central and eastern Europe. The overall prevalence of the infection was 1.38%. Phylogenetic analysis identified four new Bartonella spp. sequences, which were closely related with other Bartonella previously isolated from bats in Europe and North America.The results of this study show for the first time the presence of gltA sequences of Bartonella spp. showed considerable heterogeneity in the phylogenetic analysis resulting in six different clades. Our study demonstrated the presence of Bartonella spp. only in heart tissues of bats from Romania, with two new bat species recorded as hosts .The The online version of this article (10.1186/s13071-018-3070-7) contains supplementary material, which is available to authorized users. Bats are among the most widespread mammalian species worldwide with high local diversity and abundance. They are divided in two suborders: Yinpterochiroptera with distribution especially in the tropical regions and Yangochiroptera more widely distributed and with higher species diversity . They arBartonella is a relatively diverse group of Gram-negative, facultative intracellular, haemotropic, vector-borne, bacteria that infect a wide-range of mammals and have a global distribution. After infection, the bacteria eventually enter the erythrocytes and endothelial cells and can persist asymptomatically in a wide range of mammalian reservoir hosts such as rodents, insectivores, carnivores, and ungulates [Bartonella species in mammals is the result of a complex relationship between multiple hosts, vectors and pathogens. There are many species of Bartonella, some of them with a large host spectrum and zoonotic potential  while some others are known only from single host species [The genus ngulates –15. The ngulates , sand flngulates , lice [1ngulates , mites [ngulates  and tickngulates , 21. The species –24.Bartonella spp. has been reported with different prevalence and a high genetic diversity in bats and bat flies [Bartonella in tissues of bats is still scarce. In Europe there are two studies reporting the presence of Bartonella spp. in bat tissues, involving different species [vs Georgia). Bai et al. [Bartonella DNA and more than 25 genetic variants were identified. Urushadze et al. [Bartonella in the blood of 212 live bats by culture followed by PCR and found a 49.5 % prevalence.at flies –29. Howe species , 31. Bote et al.  investigBartonella spp. in heart tissues of different species of bats from central and eastern Europe. We primarily targeted bat species which are rarely recorded in caves , with accent on building-dwelling bats, the group with the highest contact rate with humans and potentially posing a zoonotic risk.Considering all these, the aim of our study was to demonstrate the presence and diversity of A total of 435 carcasses were collected from different countries from central and eastern Europe  between 2001 and 2016  and BhCS.1137 (5'-AAT GCA AAA AGA ACA GTA AAC A-3') [Bartonella henselae, strain (ID 54A) isolated from a cat from Israel [A PCR targeting the 370 bp of the AC A-3') . The ream Israel . AmplifigltA gene has been shown to be suitable for phylogenetic analysis among Bartonella species [Bartonella infection. Using the search query keywords ‘Bartonella bats gltA’, we retrieved from GenBank all the sequences available from bats and their ectoparasites. Furthermore, based on the available literature concerning bartonellae from bats, we produced a database, where, from each unique Bartonella gltA genotype found, we included data on the host species and the species of the ectoparasite, in the case they were present  analysis. The evolutionary history was inferred by Maximum Likelihood method based on the Tamura-Nei model . The glt species  and is cBartonella spp., the prevalence at locality level and the prevalence for each bat species and their 95% confidence interval (95% CI) were calculated.Statistical analysis was performed using EpiInfo™ 7  software. The overall prevalence of Bartonella spp. DNA. A total of 6 samples were positive (1.38%). The positive samples belonged to three bat species: Myotis cf. alcathoe , Nyctalus noctula  and Pipistrellus pipistrellus . The following species were negative (numbers of examined bats in parentheses): Barbastella barbastellus (n = 2); Eptesicus nilssonii (n = 1); E. serotinus (n = 6); Hypsugo savii (n = 9); Miniopterus schreibersii (n = 4); My.bechsteinii (n = 4); My. cf. brandtii (n = 3); My. daubentonii (n = 2); My. myotis (n = 6); My. cf. mystacinus (n = 4); My. nattereri (n = 1); Nyctalus leisleri (n = 5); Pipistrellus kuhlii (n = 8); Pi. nathusii (n = 28); Pi. pygmaeus (n = 5); Plecotus auritus (n = 7); Pl. austriacus (n = 1); Rhinolophus euryale (n = 9); R. ferrumequinum (n = 1); R. hipposideros (n = 1); and Vespertilio murinus (n = 20).Overall, 435 samples were tested for the presence of n = 6) originated from three locations in Romania: Muntele Puciosu , Cheile Bicazului  and Huda lui Papară    and four sequences isolated from North America. The third cluster consisted in different sequences isolated from the Old World . The fourth clade was the largest and most diverse and included sequences isolated from four different continents. The fifth clade comprised sequences from both Old World and New World, while the sixth clade consisted exclusively in sequences from South America, belonging to Yangochiroptera  instead of multiple markers [Bartonella sp. [Reports of  Georgia , Taiwan  Georgia , Guatema Georgia , Costa R Georgia , Kenya [ Georgia  and Chin Georgia , compare Georgia  and the  Georgia . Most ofarasites , 46, butarasites , France,arasites , Georgiaarasites  and the arasites  tested apteridae . The rep markers  and the ella sp. .Bartonella isolated from bats and their ectoparasites. The distribution of Bartonella spp. in different bat families depends also on the geographical distribution of that particular family (Table Bartonella spp. isolated from Yangochiroptera. The most diverse clade regarding the number of bat host families was clade IV: the Miniopteridae and Vespertilionidae (Yangochiroptera) and the Hipposideridae, Pteropodidae and Rhinolophidae (Yinpterochiroptera) , as this family is among the most diverse, widespread and well-studied. In Europe there are 44 bat species out of which 35 belong to Vespertilionidae [Bartonella spp. were focused mainly on this family [The global phylogenetic analysis of the sequences considered in this study showed that there is a high diversity among ly Table . Three oa) Table . Sequenclionidae  and all s family , 50, 51.B. mayotimonensis [Bartonella spp. in bats should be focused especially on those belonging to the Vespertilionidae , as the Bartonella isolated from these genera seem to be genetically related to B. mayotimonensis. Although all the positive samples from Romania were isolated from species of the family Vespertilionidae, our study did not reveal sequences related with any of the zoonotic Bartonella genotypes.So far, the pathogenicity of bat-associated bartonellae to humans remains unknown, and further studies are needed to clarify their zoonotic potential. There are reports from Finland and the USA where different Vespertilionidae bats harboured the human pathogen monensis , 50, whimonensis . Stuckeymonensis  suggesteBartonella were found in bats and their associated bat flies, suggesting that the latter may act as vectors. Bartonella spp. prevalence is higher in bat ectoparasites and have a much more genetic diversity compared with those isolated from the bats [Diverse genetic variants of the bats , 52–55.Bartonella spp., but with a low prevalence, reporting the presence of these bacteria in two new hosts . The molecular phylogenetic analysis conducted in this study revealed a high genetic diversity among Bartonella spp. isolated from bats in different parts of the world, with the presence of six major clades.This study showed that bats can harbour different strains of Additional file 1:Table S1. Samples distribution according to locality and species. (XLSX 14 kb)Additional file 2:Table S2. Detailed information regarding the sequences used in the phylogenetic analysis. (XLSX 29 kb)


This narrative review is aimed at presenting the most recent evidence on the association between attention-deficit/hyperactivity disorder (ADHD) and obesity. The review is informed by previous relevant systematic reviews and a search in Pubmed and PsycINFO up to 1 August 2019. Although the association between ADHD and obesity would seem, at first, paradoxical, in the past two decades there has been an increasing number of studies on this topic. The present review shows that there is meta-analytic evidence supporting a significant association between these two conditions, at least in adults. Growing evidence is also being published on the genetic and environmental factors underlying the association. However, the cause–effects paths, as well as the exact mechanisms explaining the association, remain unclear. Additionally, empirical evidence guiding the management/treatment of patients with the two conditions is still limited. Therefore, after almost 20 years from the first report of a link between ADHD and obesity, this association continues to be puzzling.  Following the seminal publication, in 2002, of the study by Altfas , showingThe association between ADHD and obesity may seem, at first, counterintuitive. “These children move a lot; if anything, they should be thinner compared to their non-ADHD peers” is what many lay persons or even mental health professionals may think. It goes without saying that higher than expected rates of obesity in individuals with ADHD do not rule out the possibility that underweight is also associated with ADHD, i.e., the rates of both under- and overweight may be higher in individuals with ADHD compared to those without the disorder.Building on previous evidence synthesis in the field, this review aims to provide updated evidence on a series of aspects related to the link ADHD–obesity.ADHD, Attention deficit, Attention-Deficit, Hyperkinetic Disorder, obesity, overweight. For ease of use, the present review is organized in a question and answer format. Any retrieved study  pertinent to the review questions was retained for the present review.Although it is not intended as a formal systematic review with a structured qualitative and quantitative appraisal of each pertinent study, the present narrative review was rigorously informed by available systematic reviews, complemented by recent empirical quantitative studies retrieved with a search in PubMed and PsycINFO from 20 October 2017  where all individuals with ADHD were medicated with stimulant medications.In the first of the two systematic reviews/meta-analyses, Cortese et al.  includedThe second systematic review/meta-analysis by Nigg and colleagues  includedOverall, while these two meta-analyses (from two independent groups) substantially agree on the effect of the association between ADHD and obesity when pooling studies across ages and in both sexes, they diverge in terms of the estimation of age and sex effects. However, they both agree that the relationship between ADHD and obesity is stronger in adults compared to children/adolescents. Interestingly, sex and ADHD presentation effects have been found in an additional study published after these two meta-analyses . DrawingThe two meta-analyses could not explore in detail the effect of psychiatric comorbidities associated with ADHD. In this regard, a recent study  found thn = 8106) until the age of 16, when data relevant for the study were available for 6934 participants. They found that teacher-reported ADHD symptoms in childhood significantly predicted adolescent obesity , rather than vice versa. More specifically, symptoms of inattention and hyperactivity at the age of 8 were significantly associated with obesity at 16 years of age, even after adjusting for sex, baseline BMI, physical activity, family structure change, and maternal education. The lack of a formal diagnosis of ADHD, as well as of direct measures of height and weight, are limitations that should be considered when interpreting the study results. A more recent study [n = 35,668) as well as adults . To this end, the authors used the inverse weighted variance (IVW) estimator, i.e., a linear regression of the instrument–outcome association estimates on the instrument–exposure association estimates, weighted by the inverse of the variance of the instrument–outcome association estimates. The authors found evidence indicating a positive causal effect of BMI on ADHD, rather than the opposite. The conclusion of this study should be considered in the light of the study limitations, as, whilst 77 variants were available to test the effects of BMI, only 12 variants were used to assess the effects of ADHD. Furthermore, the study used a dimensional approach, as its focus was on BMI rather than obesity/overweight; as such, the study conclusions are not comparable to those of the other studies cited in this section, which used a categorical approach (presence or absence of obesity/overweight). Whilst the mechanisms leading from obesity to ADHD may not seem straightforward to understand, it has been hypothesized that obesity may lead to ADHD symptoms via sleep disordered breathing (SDB). In fact, SDB is associated with obesity and has been shown to lead to ADHD-like symptoms [The two systematic reviews/meta-analyses described in the previous section used cross-sectional data. As such, they are not informative on temporal and cause–effect relationships. Indeed, it is possible that: (1) ADHD precedes and contributes to obesity, deregulating energy balance; (2) Obesity leads to ADHD symptoms; (3) The two disorders share common etiopathophysiological mechanisms; (4) There are bi-directional links between the two conditions, with, possibly, additional underlying common factors contributing to the association. A few studies attempting to address these issues are available to date. In the first, Cortese et al.  analysednt study  used a bOverall, considering all the available studies, it is fair to conclude the direction of the causal associations between ADHD and obesity is far from being clear, and it is likely that complex bidirectional associations, rather than simple unidirectional ones, are involved.A review informed by a systematic search performed in October 2017 [Whilst early reviews ,13 on thn = 472,735) had increased risk of ADHD  compared with siblings of index males without obesity, after adjusting for birth year of the index male and sex of the sibling. The results remained significant even after adjusting for the ADHD status of the index male . This study showed a familial co-aggregation of ADHD and obesity but not necessarily a common genetic cause, as “familial” does not equal “genetic”. Likewise, another study from an independent Dutch sample [In a large study based on studies registries, Chen et al.  observedh sample  based onIn contrast, another large Swedish registry study  , considering their involvement in ADHD and reward sensitivity . It was Another study added to our knowledge on abnormal reward mechanisms, providing a different perspective. In a sample of 25 individuals (aged 17–68 years) with obesity and 25 with normal weight, van der Oord et al.  found thDRD4, SNAP25 and 5HTR2A), but no significant differences in the scores of the neuropsychological tests were detected between patients with overweight and those without overweight. This study challenged the hypotheses from pervious reviews [Another study set out to test, in a sample of 109 boys with ADHD (7–17 years), the relationship between overweight, polymorphism in selected genes, and cold executive dysfunctions expected to lead to abnormal eating patterns via impulsivity and inattention . Tests u reviews ,13, suggA recent study has focused on eating behaviours alterations other than binge eating, exploring the relationship between food addition and ADHD symptoms in individuals with obesity. Brunault et al.  includedIn sum, the exact relationships between specific abnormal food behaviours and executive dysfunctions overweight in ADHD have not been fully elucidated and should prompt further research using well-powered samples.The review by Hanć and Cortese  reportedAn intriguing line of research has pointed to a possible role of disrupted sleep patterns. This is based on the premise that excessive daytime sleepiness (EDS), caused by sleep disturbance or manifesting itself as a primary disorder, contributes to ADHD symptoms . Indeed,Whilst at the time of the review by Hanć and Cortese  only twoA previous review  hypothesWhile until recently there was no empirical evidence in relation to this, a recent pilot study provided initial evidence supporting a possible role of inflammatory mechanisms. In this study of 52 children seen in an obesity clinic, Cortese et al.  found a To date, evidence fails to support a role of abnormal thyroid hormones in the link between ADHD and obesity. In fact, in a relatively large study  (includin = 36) compared with healthy controls (n = 40), suggesting that a low adiponectin level and high L/A may underlie the link ADHD–obesity. Unfortunately, the cross-sectional and correlational nature of the study prevents any causal inference to be drawn.A recent small study  found siA previous review by Cortese and Castellanos  noted thHowever, a randomised study highlighted the value of treating executive dysfunctions  to improve outcomes during weight loss programmes. Verbeken and colleagues  randomisWhilst no other similar randomised studies were found, the updated search retrieved the protocol of a randomised trial  aimed toAnother aspect which is related to treatment/management issues is around the specific effects of stimulants  in patiOverall, it appears that available evidence is still insufficient to rigorously guide the practice of clinicians treating the challenging subgroup of patients with ADHD presenting with co-occurring obesity. It is hoped that more rigorous randomised study designs, ideally based on pragmatic RCTs, will be used in the near future.After almost 20 years from the first study pointing to a significant association between ADHD and obesity, the association is now well established, at least in adults, on the basis of meta-analytic findings, and the underpinning causes are being progressively more investigated, although aspects related to the cause–effect links, the exact underpinning mechanisms and how treatment of ADHD impacts on obesity outcomes remain unclear. Additionally, the specific aspects of ADHD  related to obesity should be further investigated.Researchers in the field should aim to build a comprehensive biopsychosocial model that takes into account the developmental perspective to gain insight into association between ADHD and obesity. Prospective longitudinal studies, ideally including putative biomarkers, would be needed to address this from a rigorous methodological standpoint.It is also expected that the future research in this field will provide more rigorous evidence to inform clinical decision-making when treating patients with co-existing ADHD and obesity. Ideally, this line of research should rely on pragmatic randomised controlled trials, aimed at rigorously testing the possible incremental befits in screening and treating ADHD in patients with obesity.It is also hoped that researchers will take a less restrictive approaches and, rather than focusing on the relation between ADHD and, selectively, obesity, they will analyse this link within the framework of a broader association of ADHD with a number of somatic conditions. In fact, ADHD has been associated with other somatic conditions, such as asthma  (for a cUltimately, all these lines of research should contribute to provide the evidence base for a more comprehensive care of patients with ADHD.


NET, SLC6A2) gene, which have been linked to ADHD previously. Attention problems scores of the mother-rated Child Behavior Checklist (CBCL) were used in separate analyses of 88 preschoolers  recruited from the general population and 120 child psychiatry patients with ADHD diagnosis . The NET SNPs showed associations with attention problems, but the direction was different in the two groups. Regarding the promoter variant rs28386840, which showed the most consistent association, the T-allele-carrier patients with ADHD had lower CBCL attention problems scores compared to patients with AA genotype (p = 0.023), whereas T-allele-carriers in the community sample had more attention problems (p = 0.042). Based on previous reports of lower NE levels in ADHD children and the inverted-U shape effect of NE on cognitive functions, we propose that rs28386840 (-3081) T-allele, which is associated with lower NET expression  would support attention processes among ADHD patients (similarly as atomoxetine increases NE levels), whereas it would hinder cortical functions in healthy children.Among the monoaminergic modulatory neurotransmitters, norepinephrine is involved in task orienting, hence noradrenergic genetic variants have been studied in connection to attentional processes. The role of this catecholamine system is also highlighted by the selective norepinephrine transporter blocking atomoxetine, which has proved to be effective in the pharmacological treatment of Attention Deficit Hyperactivity Disorder (ADHD). In the present genetic association study three single nucleotide polymorphisms  were analyzed from the 5′ region of the norepinephrine transporter ( Attention problems have gained increasing interest during the last decades, as the proportion of children with attention deficit hyperactivity disorder (ADHD) diagnosis has risen dramatically in many countries, creating social and scientific debates . Althoug2 ∼ 0.7) for attention problems  with ADHD symptom severity but not with ADHD diagnosis per se  of the norepinephrine transporter gene  on 7300 Real-Time PCR System (Applied BioSystem). No significant deviations from Hardy–Weinberg equilibrium (p > 0.1) were detected for the NET polymorphisms in any of the tested samples. Both the clinical and the community samples were ethnically homogeneous Caucasian origin and consisted of unrelated individuals.The study was designed in compliance with the Helsinki Declaration and was approved by the Local Scientific and Research Ethics Committee of the Hungarian Medical Research Council. The participating parents (mostly mothers) provided written informed consent. The two samples and genotyping methods are described in details by For psychiatric symptom assessment, the Hungarian version of the Child Behavior Checklist CBCL,  was usedU-tests in the community sample. Quantitative analyses of estimated haplotypes were performed with the THESIAS program  as independent variable, with sex and age covariates in univariate analysis of variance in the clinical samples. Whereas CBCL T-scores were compared between the two genotype groups by Mann–Whitney  program .Z = –2.03, p = 0.042, and Z = –1.97, p = 0.049, respectively). Among patients with ADHD, the two promoter SNPs showed associations with attention problems  = 5.33, p = 0.023, η2= 0.04, observed power: 0.63; rs2242446: F = 5.53, p = 0.020, η2= 0.05, observed power: 0.64). Similar associations (with higher power) were detected in the extended child psychiatry patient sample: rs28386840: F = 11.55, p = 0.001, η2= 0.06, observed power: 0.92; rs2242446: F = 9.40, p = 0.002, η2= 0.05, observed power: 0.86). Importantly, the means of the genotype groups showed different patterns in the clinical and community samples  haplotype group showed significantly higher attention problems scores in the community sample than the most frequent A-T-C haplotype group , indicating the importance of the promoter polymorphisms.Using all three The involvement of the NE system in attentional networks and in ADHD pathogenesis has long been demonstrated . For exaNET gene polymorphisms and inattention symptom severity on the ADHD-Rating Scale among ADHD patients  T-allele have differential effects on attentional performance  could act as plasticity allele(s), resulting in opposite effects in positive and negative environments (reflecting that psychiatry patients have more stressful life events). In order to test this hypothesis, interaction analyses were performed in the community sample, where (mother-reported) stressful life events data was available. Since no significant interaction of life stress and genotype was observed, we rejected this model.We acknowledge that attention problems have multiple components, and genetic variants contributing to cortical NET promoter polymorphisms on attentional problems in a community sample of children compared to patients recruited at a child psychiatry clinic. The inverted-U shape modulatory effect can explain the observed contradictions if lower baseline cortical catecholamine levels are assumed in ADHD patients (see Figure NET genetic findings.In conclusion, our results showed opposite genetic effects of Limitations of our study include the relatively small sample size, which did not allow testing gene-gene interactions, and the high comorbidity rates in the clinical sample, thus it cannot be regarded as a purely ADHD patient sample. In addition, due to potential rater bias and cultural effects on the attention problems scale of the CBCL , our finZN conceived and managed the genetic association study and drafted the manuscript. NA carried out the genotyping and helped in manuscript preparation. ZT and EBo collected the questionnaire data at the child psychiatry clinic. EBi and KL collected the questionnaire data in the longitudinal study of healthy children. KL was responsible for data management and analyses of the community sample. MS-S and JG designed the data collection and acquired the financial support for it. All authors have reviewed and approved the 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.


A recent large-scale mega genome-wide association study identified, for the first time, genetic variants at 12 loci significantly associated with attention-deficit/hyperactivity disorder (ADHD). In this study we use a powerful polygenic approach, with polygenic scores derived from the genome-wide association study, to investigate the etiological overlap between ADHD and frequently co-occurring traits and disorders.N = 135,726) recruited by the UK Biobank. Regression analyses were conducted to investigate whether polygenic risk for ADHD is associated with related traits and disorders in this population sample. The effects of sex were investigated via inclusion of an interaction term in the models.Polygenic risk scores for ADHD derived from the mega genome-wide association study  were computed in a large-scale adult population sample , neuroticism , depression , anxiety , risk taking , alcohol intake , smoking , alcohol dependency , and negatively predicted verbal-numerical reasoning . Polygenic risk scores did not significantly predict schizophrenia or bipolar disorder, although this may be because of the small number of diagnostic cases. We found no interaction effects between polygenic risk for ADHD and sex on any phenotypes.Polygenic risk for ADHD significantly and positively predicted body mass index (Our findings suggest that common genetic variation underlying risk for clinically diagnosed ADHD also contributes to higher body mass index, neuroticism, anxiety and depressive disorders, alcohol and nicotine use, risk taking, and lower general cognitive ability in the general population. These findings suggest that the co-occurrence of several traits with ADHD is partly explained by the same common genetic variants. SEE COMMENTARY ON PAGE 577A recent mega genome-wide association study (GWAS) was the first to identify 12 loci significantly associated with attention-deficit/hyperactivity disorder (ADHD) Previous GWAS and candidate studies failed to identify rare and common genetic variants underlying ADHD that explain more than a small fraction of its heritability ADHD has a prevalence rate of around 5.3% in childhood and 2.5% to 2.9% in adulthood rg = 0.21–0.26), educational and cognitive measures (rg = −0.25 to 0.54), depression (rg = 0.48), BD (rg = 0.25), schizophrenia (rg = 0.22), and smoking (rg = 0.38–0.48), but not neuroticism and obsessive-compulsive disorder Family and twin studies suggest that several of these associations between ADHD and co-occurring traits and disorders are moderately to substantially explained by genetic influences While associations between ADHD and co-occurring impairments are well documented, our knowledge of the shared etiological influences underlying these co-occurrences is still limited with regard to the magnitude and type of genetic variants implicated in the genetic associations. The advantage of using a polygenic approach to study the genetic associations between phenotypes is that 1) we use molecular genetic data that do not rely on assumptions of relatedness, as in twin studies; 2) the design captures the polygenic nature of complex traits and disorders; and this design in turn 3) increases power to detect significant effects in studies compared with those considering only the most associated variants or candidate genes. In contrast to LDSR, the polygenic scoring method uses individual-level SNP, resulting in greater statistical power data and allowing for direct testing of interaction effects.In this study, we use a powerful polygenic approach exploiting PRSs derived from the recently published mega GWAS on ADHD to test whether genetic variants that contribute to ADHD also influence frequently co-occurring traits and disorders in a large-scale adult population sample. A greater understanding of why ADHD often co-occurs with other impairing conditions may in turn improve preventative strategies and treatment for affected individuals. We further investigate whether the genetic overlap between ADHD and co-occurring features varies as a function of sex. Although a recent study suggested a near complete overlap of common genetic variants associated with ADHD between males and females https://www.med.unc.edu/pgc/results-and-downloads). This GWAS contains data from 55,374 children and adults , and 8,047,421 SNPs. Twelve independent loci were significantly associated with ADHD, and polygenic risk calculated from the GWAS explained on average up to 5.5% variance in ADHD case-control status, when using five different sets of discovery and independent target samples. The SNP-based heritability was calculated as 0.22 We used the recently published mega GWAS on ADHD as the discovery dataset http://www.ukbiobank.ac.uk) We used baseline data from the UK Biobank Study  or the UK Biobank axiom array . Details on genotyping, quality control, and imputation procedures can be found on the UK Biobank website (http://www.ukbiobank.ac.uk/scientists-3/genetic-data/) and Sudlow et al.p < 10–8), and missingness (>0.02), and removed participants based on missingness (>0.01), relatedness (>0.088 [r∼ = .25]), gender mismatch, and non-Caucasian ancestry. A total of 152,729 blood samples were genotyped using either the UK Biobank Lung Exome Variant Evaluation array (2), was measured during the initial assessment. BMI values were excluded if data on either height or weight were missing.BMI, which is constructed from weight and height (kg/cmr = .65) and a high genetic correlation with a general factor of cognitive ability  Participants completed a verbal-numerical reasoning test, consisting of 13 multiple choice questions  answered within a 2-minute time period . The tesNeuroticism was measured using 12 items  from thePrimary (the most resource-intensive condition) or secondary ICD-10 diagnoses  and self-report measures (reports of having experienced a disorder during an interview with a nurse) were used to identify individuals who had experienced instances of anxiety and depressive disorders, BD, and schizophrenia  diagnosed with oppositional defiant disorder, conduct disorder, or autism spectrum disorder. The low prevalence rate of ADHD and these other disorders in the UK Biobank is likely related to the older age of the sample (40–73 years of age), as they are most often diagnosed in childhood but were not as commonly recognized when participants were school-aged children.We did not investigate participants with ADHD because only 7 individuals had an ICD-10 diagnosis (secondary) for ADHD or were taking stimulant medications  in our genotyped sample. There were also few participants  r2 ≥ .1 (250-kb window) was used for clumping to remove SNPs in linkage disequilibrium. Logistic and linear regression models were used to estimate associations between PRSs and phenotypes in the UK Biobank. PRSs were calculated at a large number of p value thresholds for SNP inclusion (“high resolution scoring”) p Value thresholds were between pT = 0 and pT = 0.5 at increments of .001. Results are presented where the most predictive PRS is identified for each phenotype. We set a conservative significance threshold of p < 2.1 × 10−4 for the main analyses on traits of interest and “control” traits, based on testing the most predictive PRS across 19 phenotypes .We controlled for population stratification by conducting analyses with imputed markers and 15 principal components as covariates. We included birthplace, age, and sex as covariates in all analyses, and also batch, in order to control for any genetic differences associated with the batches that samples were analyses in or the genotyping platforms. The 10−4 see . In the p = 4.5 × 10−129) predicted BMI  (PRS for ADHD significantly (T = .44) , and theT = .44) . Mean BMp = 4.5 × 10−36) predicted verbal-numerical reasoning scores  (PRS for ADHD significantly (T = .42) , and theT = .42) . Verbal-p = 2.2 × 10−24) predicted neuroticism  and the quantile plot demonstrates that neuroticism scores increase with higher polygenic load for ADHD (R2 = .002%), fed-up feelings (R2 = .20%), feelings of loneliness and isolation (R2 = .19%), miserableness (R2 = .13%), irritability (R2 = .09%), being tense/highly strung (R2 = .07%), guilty feelings (R2 = .05%), and having easily hurt feelings (R2 = .05%). The PRS did not predict suffering from nerves, often worrying after embarrassment, or being a nervous person or a worrier.PRS for ADHD significantly  predicted depressive disorder  and suggestively (p = 2.8 × 10−4) predicted anxiety  but not BD or schizophrenia  predicted risk-taking , alcohol intake frequency  and dependency , and smoking . Quantile plots suggest that all of these relationships were positive in nature (PRS for ADHD significantly (n nature . A signiWe found no significant PRS by sex interaction effects for any of the target phenotypes .Table 2Pp < 2.1 × 10−4) and negatively predicted height  and age , but not any of the remaining six control phenotypes ; however, the association between PRS and age remained and was significant in both males  and females . When we reran all the main analyses controlling for educational achievement and BMI, which were the two additional covariates in the PRS–height model, the overall pattern of results remained the same, although effect sizes decreased for most traits (PRS for ADHD significantly (enotypes . After cenotypes , which ht traits .Table 3PUsing PRSs derived from the recently published mega GWAS Individuals with many risk alleles for ADHD were more likely to have higher BMI than those with few risk alleles. There is limited research investigating why ADHD and high BMI often co-occur, but our findings, together with recent findings using LDSR Polygenic risk for ADHD was significantly associated with lower cognitive ability, which is in line with previous twin and molecular genetic studies Polygenic risk for ADHD significantly and positively predicted neuroticism, including individual items such as mood swings and irritability. Two recent studies failed to find any genetic correlation between ADHD and neuroticism using LDSR PRSs for ADHD also predicted depression, and anxiety at a suggestive level, which is in line with findings from twin and genome-wide studies Individuals with many risk alleles for ADHD were more likely to display alcohol dependency, have higher alcohol intake frequency, and be smokers and risk-takers compared with those with few risk alleles. Previous genome-wide studies reported significant genetic associations between ADHD and smoking Overall, our findings lend support for the continuous nature of ADHD across the entire population. We find that common risk alleles that contribute to clinically diagnosed ADHD also influence common traits and disorders in the general population, across ages, which suggests that ADHD symptoms represent continuous traits and that similar genetic influences may be present in younger and older individuals. This fits well with the current understanding of ADHD based on evidence from behavioral, family-based, and genetic studies To investigate if our significant results could be the result of type I errors, we examined if PRSs for ADHD significantly predicted several “control” phenotypes that were not expected to be associated with polygenic risk for ADHD. Out of the eight “control” traits, only age was significantly predicted by ADHD PRS. It is possible that this association is caused by some real effect, such as genetic influences on ADHD being stronger during certain developmental periods, for example in childhood, when the prevalence of ADHD is the highest. Twin studies suggest that the heritability of childhood ADHD is stronger than in adult ADHD, but this may also be due to rater effects An advantage of using a large dataset and the PRS approach is that we could directly investigate sex differences in the relationship between PRSs and the target phenotypes. A recent study based on the ADHD mega GWAS data found a strong genetic correlation for ADHD across sex and no difference in polygenic load across sex One should interpret our findings in light of the study limitations. Our study participants were between 40 and 73 years of age, had a lower prevalence of mental health disorders, and were recruited within the United Kingdom. It would be informative to investigate the generalizability of our findings by replicating the analyses using participants of different age groups and from different populations. Selection bias of the sample could also have influenced the associations we report In conclusion, higher polygenic load for clinical ADHD was associated with higher BMI, neurotic and risk-taking behavior, anxiety and depressive disorders and substance use, and lower general cognitive ability in the general population. These findings suggest that the co-occurrence of several traits and disorders with ADHD are partly explained by the same common genetic factors. Further investigations are needed to determine the specific neurobiological mechanisms associated with the shared genetic etiology between ADHD and co-occurring features.


Both the ROI and the whole-brain analyses showed that the comorbid ASD+ADHD group compared to controls, and for the ROI analysis relative to the other patient groups, had significant under-activation in right inferior frontal cortex (IFG) a key region for duration discrimination that is typically under-activated in boys with ADHD. The findings show that in young adult males with pure ASD, pure ADHD and comorbid ASD+ADHD with no intellectual disability, only the comorbid group demonstrates neurofunctional deficits in a typical duration discrimination region.Attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) often co-occur and share neurocognitive deficits. One such shared impairment is in duration discrimination. However, no studies using functional magnetic resonance imaging (fMRI) have investigated whether these duration discrimination deficits are underpinned by the same or different underlying neurofunctional processes. In this study, we used fMRI to compare the neurofunctional correlates of duration discrimination between young adult males with ASD ( Autism spectrum disorder (ASD) is characterized by difficulties in reciprocal social communication/interaction and stereotyped and repetitive behaviors, while attention-deficit/hyperactivity disorder (ADHD) is characterized by age-inappropriate symptoms of inattention, hyperactivity and impulsivity . Both coPerceptual timing, i.e., “the ability to estimate explicitly attended temporal intervals” , could bExperimental studies of time perception have consistently reported impaired task performance in ADHD see , 14, 25], 2514, 2Experimental findings have also suggested an impairment of time perception in people with ASD –44 althoSeveral studies, however, have compared the two disorders in other EF domains e.g., , 48, 49], 4948, 4To address the gap in the literature, this study explores the neural correlates of time discrimination in young adult males with ASD, ADHD, and ASD+ADHD relative to age-matched controls. We were particularly interested in the potential impairments in the comorbid group compared to the pure groups to elucidate the mechanisms underpinning the co-occurrence of ASD and ADHD, as this information could be useful clinically for formulating disorder-specific treatments. Based on previous fMRI studies of time perception in ADHD, we hypothesized functional impairments in regions previously implicated with timing deficits in the ADHD group, i.e., in ACC/SMA, IFG, caudate, IPL and cerebellum , 34–38, Participants were 107 young adults aged 20–27 years with ASD, ADHD, ASD+ADHD, and TD and full-scale intelligent quotient (FSIQ) ≥ 70, estimated using the Wechsler Abbreviated Scale of Intelligence-II (WASI-II) . Only maIn the ASD group, 15 participants had clinical diagnoses confirmed by consultant psychiatrists specialized in ASD  and eight had research diagnoses of ASD through the SNAP study , according to the International Classification of Diseases (ICD-10) criteria . Twenty-All pure ADHD participants met the current DSM5 diagnostic criteria for ADHD, fifteen with combined, nine with predominantly inattentive and one with predominantly hyperactive presentation, diagnosed by consultant psychiatrists in specialist adult ADHD clinics. Twenty-two diagnoses were supported by the Diagnostic Interview for Adult ADHD DIVA 2.0)  and thre.0  and tIn the ASD+ADHD group, eighteen participants had clinical ASD diagnoses  and six had research diagnoses through SNAP , based on the ICD-10 criteria. Twenty-one diagnoses were supported by the ADOS and/or the ADI-R. Eleven met the current cut-off criteria for ASD on at least one of these measures. Three without ADOS or ADI-R reports received childhood ASD diagnoses from consultant psychiatrists in a specialist neurodevelopmental clinic supported by the DISCO (no current scores). Fifteen had clinical DSM5 ADHD diagnoses, 11 of which were supported by current scores of DIVA 2.0, four clinical diagnoses were supported assessment on the CAADID or other psychiatric interview methods (no current scores). Nine participants had a significant history of ADHD symptoms assessed through SNAP  and met current ADHD DSM5 criteria on the Young Adult Psychiatric Assessment (YAPA) . SixteenThe TD participants were from local communities, had no psychiatric disorders, were medication-free and scored below clinical cut-off for ADHD and ASD traits on the Conners' Adult ADHD Rating Scale (CAARS)  and the ADHD traits were measured using the ADHD index on the CAARS and the hyperactive/impulsive and inattention domain on the Strengths and Difficulties Questionnaires for adults . Autistic traits were indexed using the total SRS-2 score. All participants completed self-report measures, corroborated by informants (parents/partner/siblings) for those in the clinical groups.This block-design time discrimination task –37, 67 c*-weighted MR images parallel to the inter-commissural plane covering the entire brain. The 5-min scan produced 153 volumes in time series. A whole-brain high resolution structural T1-weighted scan  was acquired in the inter-commissural plane with TR/TE = 7.312/3.016 s, 196 slices, FOV = 27 × 27 cm, 256 × 256 matrix and slice thickness of 1.2 mm.Neuroimaging data were acquired on a General Electric MR750 3T scanner  at King's College London. The scanner's body coil was used for RF transmission while an 8-channel head coil was used for signal reception. The echo planar image (EPI) gradient-echo pulse sequence  was used to acquire 41 consecutive, top-to-bottom, slices of T2Each participant's echo-planar imaging (EPI) data were slice-time corrected, realigned, co-registered to the individual's structural T1-weighted scan, segmented, normalized to the Montreal Neurological Institute (MNI) EPI template and smoothed with an 8-mm Gaussian kernel. Statistical analyses were completed in two steps on the Statistical Parametric Mapping (SPM8). At the subject-level, BOLD response was predicted using a vector of onsets and durations convolved with the canonical hemodynamic response function. Six nuisance motion regressors  and separate regressors for each spike (>1 mm) controlled the effects of volume-to-volume head motion and abrupt movements. A high-pass filter (128 s) was applied and a first-order autoregressive model corrected the time series correlation. The contrast DD > TOJ indexed neural correlates of time processing.p < 0.05, family-wise error corrected (FWEcor) and a voxel threshold of p < 0.001. Between-group activations were analyzed using univariate ANCOVA with group as independent factor, covarying total frame-wise head displacement, in spherical region of interests  associated with perceptual timing in the general population, drawn from a meta-analysis .Within-group activations (reported in Supplement) were analyzed at the second-level analysis with a cluster extent threshold of analysis , in the analysis  for postpost-hoc pairwise multiple comparisons were corrected with the Tukey-Kramer method. Correlations between BOLD activations and task performance or phenotypic traits were conducted per group.Phenotypic, behavioral, and extracted BOLD data were analyzed using IBM SPSS Statistics 22 . Demographic data and phenotypic reports were analyzed using univariate ANOVAs. Task performance measures  were analyzed using a 4 × 2 mixed-design ANOVA (Group × Condition), prior which error rates were square-rooted to normalize their distribution F = 4.9, p = 0.003], which was higher in the ADHD (p = 0.012), TD groups (p = 0.033) and, at trend level, the ASD+ADHD (p = 0.089) relative to the ASD group. Groups differed in self-rated ADHD index , the SDQ score  and the informant-rated scores for these measures , with post-hoc t-tests indicating higher ADHD symptoms in the ADHD and ASD+ADHD groups than the TD (ps < 0.001) and the ASD groups (ps < 0.001) according to the young adults, which was corroborated by informant-ratings. Self-reported autistic traits were higher in all clinical groups  than controls , although informant-rated ASD traits  but no main Group effect  or Group × Condition interaction effect  were observed.Errors, MRT and SDRT were greater during DD than TOJ  and was covaried in the second-level analysis.Group difference in the total volume-to-volume head movement in the x-, y-, and z- rotation and translation was significant .The novel finding of right IFG under-activation in the ASD+ADHD group during DD in the ROI and the whole-brain analyses indicate that the addition of ADHD symptoms in adults with ASD lead to increased neurofunctional impairments during DD. This interpretation extends, in the domain of time perception, a previous finding by Chantiluke et al.  based onAnalyses of behavioral measures suggest comparable task performance across all participant groups, which was unexpected in people with ADHD where duration discrimination deficits have been reported e.g., , 26–28].–28.26–28A strength of the study is the robust characterization of diagnoses of ASD and ADHD in the majority of patients, including the use of ICD-10, DSM5, ADI-R, ADOS, DIVA 2.0, and CAADID, as appropriate . One weakness was the IQ difference across groups which resulted in altered findings of the exploratory whole-brain analysis when IQ was covaried. However, the use of ANCOVA to correct for IQ when it is intrinsically different between groups  and In summary, only young adult males with comorbid ASD+ADHD showed reduced activation in right IFG during duration discrimination relative to healthy controls and the pure groups who were unimpaired. The findings suggest that right IFG is not neurofunctionally impaired in young adults with ADHD or ASD during time perception, although the finding in the ADHD group particularly has to be viewed in light of the possible moderating influence of IQ and medication use among the participants in this study.SL, KR, and ES conceptualized the study and contributed to manuscript preparation. SL conducted the recruitment and data collection. SL and OO analyzed the data. DL contributed to the manuscript preparation. SW, AD, CM, KA, and VS conducted recruitment and contributed to the manuscript preparation.KR has received grants from Lilly and Shire pharmaceuticals and speaker's bureau from Shire, Lilly and Medice. The remaining 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.


Adaptive behavior requires the adjustment of one’s behavioral repertoire to situational demands. The learning of situationally appropriate choice behavior can be operationalized as a task of Conditional Discrimination Learning (CDL). CDL requires the acquisition of hierarchical reinforcement relations, which may pose a particular challenge for children with Attention Deficit Hyperactivity Disorder (ADHD), particularly in light of documented deficits in short-term/working memory and delay aversion in ADHD. Using an arbitrary Delayed Matching-To-Sample task, we investigated whether children with ADHD (N = 46), relative to Typically Developing children , show a deficit in CDL under different choice delays  and whether these differences are mediated by short-term/working memory capacity and/or delay aversion. Children with ADHD demonstrated poorer CDL than TD children under 8 and 16-second delays. Non-delayed CDL performance did not differ between groups. CDL differences were not mediated by short-term/working memory performance or delay aversion. Moreover, CDL performance under an 8-second delay was a better predictor of clinical status than short-term/working memory performance or delay aversion. CDL, under conditions of delay, is impaired in children with ADHD. This may lead to difficulties discriminating between different situational demands and adapting behavior according to the prevailing reward contingencies or expectations. In daily life, we are constantly confronted with situations that require us to make choices that carry consequences. A child may choose to do a chore that is boring but will yield praise eventually, or go play and have fun at the risk of later getting scolded. It is generally accepted that this real-life choice behavior is driven by the learned consequences that follow our choices. In reality, however, the consequences of our choices are often context-specific  . AdjustiWhile clinically, children with Attention Deficit Hyperactivity Disorder (ADHD) often appear to struggle with behavioral adjustment to changing reinforcement contingencies  and to mADHD is often seen as involving the neurodevelopmental dysregulation of processes that control cognitive functions . This leMotivational deficits are also thought to contribute to ADHD symptomatology ,24,25,26As with working memory, delay aversion cannot account for all symptoms of ADHD; the effect size for differences between children with ADHD and TD children on delay aversion tasks is generally small . Like wo1 or S2) together with different choice stimuli . Which choice is correct, is conditional on the sample stimulus presented; e.g., when S1 is presented, the correct response is C1, and when S2 is presented, the correct response is C2. The sample stimuli and choice stimuli bear no intrinsic relationship; the sample-to-choice associations need to be learned [Delayed Matching-To-Sample task (aDMTS), a time interval is moreover inserted between the offset of the sample stimulus and the onset of the choice stimuli. Although to the best of our knowledge not experimentally tested, some researchers attribute delay-related performance impairments to short-term memory [An established protocol to assess CDL in clinical and non-clinical samples is the arbitrary Matching-To-Sample task (aMTS) ,31. In a learned . In an am memory ,34, wherm memory ,36. Besim memory .As far as we are aware, only one study has investigated CDL in children with ADHD . In a moFirst, based on behavioral manifestations of ADHD, we hypothesized that a CDL deficit might be involved. When limited memory load was involved (no sample-choice stimuli delay), we predicted that children with ADHD would exhibit a deficit in CDL, compared to TD children, and would thus perform more poorly on an aMTS task ,37. WhenFifty-one children with an existing clinical diagnosis of ADHD volunteered for the study. ADHD diagnoses were confirmed with the Diagnostic Interview Schedule for Children, Parent Version (PDISC) . Fifty-sr = 0.86) with full-scale IQ scores and have satisfactory reliability [For all participants: (1) An estimated Full-Scale IQ ≥ 80, as measured by the Block Design and Vocabulary subtest, short version of the Dutch Wechsler Intelligence Scale (WISC) . Resultsiability . (2) Preiability . Particiiability . (3) Absiability .For ADHD: A prior clinical diagnosis of Attention Deficit Hyperactivity Disorder according to the DSM-IV, established by a psychologist or psychiatrist and validated by the PDISC. The PDISC is a structured DSM-IV-based interview with adequate psychometric properties .For TD: Scoring within the normal range (below the 90th percentile) on the ADHD subscales of the DBDRS and absence of any other psychiatric disorder as reported by the parents.1 or S2) followed by a retention interval and two choice stimuli (C1 & C2) [1 is arbitrarily assigned to be the correct response in the presence of S1, whereas selecting C2 is the correct response for S2 [Our CDL task involved a widely-used DMTS procedure ,34,37 anC1 & C2) . Their tC1 & C2) ,43. To ce for S2 ,43. Givee for S2 .1 or S2) on the touch screen, accompanied by a sound to make children attend to the screen. To ensure optimal attention of the participant during each trial, the task was self-paced (the stimuli stayed on the screen until the participant responded by touching the stimuli on the screen). After pressing the sample stimulus, three choice stimuli appeared . The third choice stimulus was added as a distractor to increase task difficulty, based on a series of pilot studies with TD children of the same age as those in the current study. Pilot testing showed that with 2 sample and 2 choice stimuli, a high percentage of children reached maximum performance, whereas, with 2 sample and 4 choice stimuli, the task was too difficult for most children. To identify the relevant associations (S1-C1 and S2-C2), children were verbally guided through the practice phase [1 or S2) and the position of the three choice stimuli  was determined randomly for each trial (12 options). The correct sample-choice association was determined in advance and was not counterbalanced. A correct choice was rewarded with a smiley face , and an incorrect response was followed by a red cross. The stimuli were presented on a white 15-inch touch screen. The sample and choice stimuli were black and white, measuring 5 cm by 5 cm, and the feedback stimuli 10 cm by 10 cm.Modeled on earlier research , the tasce phase . For thethe percentage of correct trials per delay  [In the test phase, three different delays were applied between the presentation of the sample stimulus and the appearance of the choice stimuli . The sample and choice stimuli were again abstract figures, similar to the ones used in the final trials of the practice phase. During the delay, a blank screen was presented. The 0-seconds delay test involved 36 trials . The order of the delay blocks was fixed, to minimize within-group variability, due to order effects. With every new block of trials, new stimuli were used, and new associations had to be acquired. The outcome measure of interest was or 16 s) , calculaCorsi Block Tapping Task (CBTT) The digital CBTT is a computerized version of the Corsi Block Tapping Test , developThe Maudsley Index of Delay Aversion (MIDA) is a game-based computer task developed to assess delay aversion in children . During Before participating, parents and children were informed about the study and gave their written consent to participate. While the structured interview and questionnaires were being administered to the parents, the experimental tasks were completed by the children in a quiet, distraction-free room. All participants completed the CDL task  first, followed by either the MIDA  or the CBTT  and other tasks not part of the current study. Finally, they completed the Block Design and Vocabulary subtests of the WISC-III-NL. Counterbalancing of MIDA and CBTT over participants was based on diagnosis, age, and gender, resulting in 8 different testing orders. At the end of the test session (100 min), parents received ten euros, and children received a small gift.The study was conducted per the Declaration of Helsinki and its later amendments. The Social and Societal Ethics Committee of the Faculty Psychology and Educational Sciences at KU Leuven approved the study (G-2015 01 156).F = 9.31, p = 0.003, η2p = 0.086. Ninety-five percent of children in the TD group obtained scores on the DBDRS within the normal range for inattention and hyperactive/impulsive symptoms, i.e., between the 50th and 63.1th percentile. Children in the ADHD group all scored between the 90.9th and 97.7th percentile for inattention and hyperactive/impulsive symptoms.Six children (five ADHD and one TD) did not meet the inclusion criteria, and their data were excluded from the dataset . Out of 46 children who met DSM-IV criteria  for a diMissing task-data occurred as a consequence of apparatus malfunction (<10%) and were missing completely at random. Data were analyzed using the statistical package SPSS version 25 . Before d = 0.50) at α = 0.05 [For the CDL data, repeated measures ANOVA was conducted on the percentage of correct choices with delays as Within-Subjects Variables and group (ADHD/TD) as a Between-Subjects Factor. Group differences in visual-spatial short-term memory, visual-spatial working memory, and delay aversion were explored with a Multivariate ANOVA. To test if the relationship between ADHD and the percentage correct trials on the aDMTS (8 and 16 s) is mediated by short-term memory, working memory, or delay aversion, a multiple regression analysis with a 5000 bootstrap resamples, using a 95% confidence interval, was conducted using the process tool in SPSS . To inveα = 0.05 .χ2 (2) = 6.62, p = 0.037 of the 3 (delays) × 2 (group) repeated measures ANOVA; thus degrees of freedom were corrected using Greenhouse–Geisser. There was a significant interaction effect between delay and group in the expected direction, F = 3.52, p = 0.034, ηp2 = 0.034. Group comparisons, using Multivariate Analysis of Variance, indicated that the performance of children with ADHD and TD children did not differ significantly with a 0-second delay, but was significantly different at delays of 8, F = 12.94, p = 0.001, ηp2 = 0.116 and 16 s, F = 7.60, p = 0.007, ηp2 = 0.071; children with ADHD made fewer correct responses than TD children with delays of both 8 and 16 s. Controlling age and IQ strengthened this interaction effect .Mauchly’s test indicated that the assumption of sphericity was violated for the main effect of delay F = 21.83, p < 0.001, ηp2 = 0.181 and a main effect of Group, F = 7.95, p = 0.006, ηp2 = 0.074. Overall, the TD children performed better compared to ADHD children, and within-group contrasts indicated that performance under each of the three delays  differed significantly Fdelay0-delay8  = 41.36, p < 0.001, ηp2 = 0.295, Fdelay0-delay16  = 15.56, p < 0.001, ηp2 = 0.136, Fdelay8-delay16  = 5.94, p = 0.017, ηp2 = 0.057 (t(54) = −2.07, p = 0.043; no other paired comparisons were significant. Both groups made the most correct choices (highest percentage) with the 8-second delay, followed by the 16 s and 0 s delay ; Group .In addition to the significant interaction, there was a main effect of Delay,  = 0.057 . Of note s delay . Both maF = 4.62, p = 0.034, ηp2 = 0.050, but not the visual-spatial working memory task F = 2.50, p = 0.121, ηp2 = 0.027. On the delay aversion task, the MIDA, children with ADHD chose delayed reward less often, compared to the TD children, F = 4.04, p = 0.048, ηp2 = 0.044. When controlling for IQ and age, this effect remained significant (p = 0.044). The group difference for visual-spatial short-term memory was no longer significant (p = 0.064) following covariance analysis.Results of Multivariate ANOVA showed there was a significant difference between children with ADHD and TD children on the visual-spatial short-term memory task, 1 = −1.02, p = 0.034) and delay aversion  but not on working memory. These variables, nonetheless, do not influence the performance of CDL under delays of 8 and 16 s. The bootstrap confidence intervals for all indirect effects included zero and, therefore, were not significant. Thus, clinical caseness of ADHD did not affect performance on a CDL task (8 or 16 s) through working memory, short-term memory, or delay aversion, but the effect between ADHD and CDL was direct   were used as outcome measures in the mediation analysis. Results showed that having ADHD did significantly predict performance on short-term memory (a045) see .p = 0.004, odds ratio = 0.031). The odds ratio showed that children with ADHD would have a lower percentage of correct trials with a delay of 8 s, and TD children would score higher. When using performance with a delay of 16 s, this was also the only predictor that significantly contributed to the model, . Without predictors, the overall prediction success of the model was 50.6% and increased to 68.2% with a delay of 8 s and to 62.9% with a delay of 16 s. Age and IQ were not significant predictors when added into both regression models.Additionally, binary logistic regression analyses were conducted to investigate the independent effects of short-term memory, working memory, delay aversion, and delay, 8 or 16 s (separately), on the group (ADHD vs. TD). When adding working memory, short-term memory, and delay aversion together with an 8-second delay in the regression, only the delay made a significant contribution to the model , that are implicated in ADHD.As predicted, children with ADHD performed more poorly than TD children on the CDL task under delay conditions, i.e., when an 8 or 16-second delay was introduced between the sample and choice stimuli. Contrary to our expectations, there was no difference in the performance of the two groups with a 0-second delay. Anticipated differences in delay aversion and short-term visual-spatial memory performance between children with ADHD and TD children were found. Children with ADHD were more delay-averse than TD children and obtained lower scores on a test of short-term memory. Performance differences in visual-spatial working memory were not significant. The hypothesis that both memory (short-term and/or working memory) and delay aversion would mediate the relationship between group membership (ADHD/TD) and CDL was not supported by mediation analyses, rather there was a direct effect of clinical caseness, i.e., between having a clinical diagnosis of ADHD and performance on the CDL task under delays of 8 and 16 s. Finally, CDL performance was the best, and only significant, predictor for classifying children with ADHD, with performance under the 8-second delay the best predictor. Together these findings suggest that a basic reinforcement learning process like CDL, Linking our results to daily life behavior, it would seem that children with ADHD are as able as TD children to identify or discriminate the situation/context (sample stimuli) and learn the conditions under which adaptive behavior (choice stimuli) will be reinforced when there is a limited delay (0 s) between the appearance of the context and the required behavioral response. However, when a delay is imposed, children with ADHD are less likely than TD children to perform the expected (adaptive) behavior. This is consistent with clinical reports that children with ADHD fail, or are less effective in, adapting their behavior to situational demands . In the The observed group differences in CDL performance might be interpreted according to theoretical constructs that emphasize the integration of contextual information as an important contributor to children’s behavioral outcome. According to Nigg and Casey , childreExtending Nigg and Casey’s theory to the current findings, the imposed delay might contribute to reducing the salience of the contextual cue. This is suggested by the current results where group differences only emerge when there is a delay between the presentation of the context (sample stimuli) and the child’s action (choice stimuli). Björne and Balkenius in their commentary on the Dynamic Developmental Theory , proposeIn addition to poorer integration of contextual cues, or memory for such information, it is important to consider other possible explanations for the current findings. The first of these relate to the symptoms of ADHD. Inattention and distractibility are core symptoms of ADHD. The introduction of delays to the CDL task may have served to reduce the attention of children with ADHD to the sample stimuli-choice stimuli association. Alternatively, having experienced a period of waiting, the children with ADHD might have responded more quickly/impulsively when the choice stimuli appeared. Failure to pay adequate attention to the sample-choice stimuli association and/or responding without careful consideration of available choices would likely reduce task performance. Although delay aversion did not mediate CDL performance, reward sensitivity might have still contributed to task performance. Tripp and Alsop proposed that children with ADHD are more influenced by the last reward received and are less able to integrate their history of reinforcement over time than TD children . When deAs noted earlier, working memory performance was not significantly different between the ADHD and TD groups, nor did it mediate the relationship between group membership and CDL performance. This was somewhat surprising as differences in working memory are commonly reported in children with ADHD, although not in all studies , and thoPerformance on the MIDA task (delay aversion) also failed to mediate the relationship between group membership and CDL performance under conditions of delay. The lack of association between performance on the CDL task and the delay aversion task might be related to differences in the way these tasks allow the children to respond to delay. Unlike the delay aversion task, the CDL paradigm did not allow the participants to reduce the imposed delay neither by responding to reduce the waiting time nor by allowing them to engage in behaviors that would distract them from the experience of waiting. Summarizing, CDL might involve/require other different cognitive or motivational processes than those measured by the CBTT and MIDA.As indicated in In summary, our results point towards difficulties in learning/conditioning of the adaptive behavioral response in ADHD, crucially only when a delay is present between the situational cue and the required behavior. This suggests that the capacity to adjust choice behavior to situational demands or reinforcement contingencies is a distinct process and unrelated to other pathways thought to lead or contribute to ADHD .Despite the many strengths of the current study, including sample size, group assignment, and the CDL paradigm itself, some limitations need to be acknowledged that reduce the interpretations that can be made. In relation to the sample itself, symptom severity in the ADHD group may be moderate only. In addition to reducing the generalizability of the findings to more impaired samples, this may have restricted the range of scores on the predictor variables, making it more difficult to demonstrate mediation. While the sample size is good, the distribution of ADHD subtypes did not permit us to assess mediation effects in more homogenous subsamples. While care was taken in piloting the task to establish the appropriate difficulty level, additional practice trials might be needed ahead of testing to ensure participants are comfortable with the task.The findings of the current study have important implications for managing and/or accommodating the behavioral difficulties of children with ADHD. The adaptive choice behavior of children with ADHD does not differ from that of TD children when contextual cues are salient/in close temporal proximity to the behavioral choice/response. When delays are introduced, children with ADHD are less able than TD children to use contextual cues to guide their behavior. The precise mechanisms underlying this reduced efficiency of situational cues/context are uncertain, but the findings are clear.For children with ADHD, it will be important to reduce delays between the introduction of a new situation/context and requiring the child to respond. This is not always possible in daily life; however, the impact of a delay may be lessened by making the context more salient for the child through the use of stimulus control techniques. According to nigg and casey , childre1 after the presentation of S1 will result in outcome O1, while correctly choosing C2 after the presentation of S2 will result in a different outcome O2 [Another intervention that may enhance CDL under conditions of delay is a Differential Outcomes procedure (DO) ,57,58. Itcome O2 . In DO,