Heritability of attention-deficit hyperactivity disorder in adults

Intergenerational transmission of ADHD behaviors: genetic and environmental pathways

BACKGROUND

We investigate if covariation between parental and child attention-deficit hyperactivity disorder (ADHD) behaviors can be explained by environmental and/or genetic transmission.

METHODS

We employed a large children-of-twins-and-siblings sample (N = 22 276 parents and 11 566 8-year-old children) of the Norwegian Mother, Father and Child Cohort Study. This enabled us to disentangle intergenerational influences via parental genes and parental behaviors (i.e. genetic and environmental transmission, respectively). Fathers reported on their own symptoms and mothers on their own and their child's symptoms.

RESULTS

Child ADHD behaviors correlated with their mother's (0.24) and father's (0.10) ADHD behaviors. These correlations were largely due to additive genetic transmission. Variation in children's ADHD behaviors was explained by genetic factors active in both generations (11%) and genetic factors specific to the children (46%), giving a total heritability of 57%. There were small effects of parental ADHD behaviors (2% environmental transmission) and gene-environment correlation (3%). The remaining variability in ADHD behaviors was due to individual-specific environmental factors.

CONCLUSIONS

The intergenerational resemblance of ADHD behaviors is primarily due to genetic transmission, with little evidence for parental ADHD behaviors causing children's ADHD behaviors. This contradicts theories proposing environmental explanations of intergenerational transmission of ADHD, such as parenting theories or psychological life-history theory.

Attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD; also known as hyperkinetic disorder) is a common neurodevelopmental condition that affects children and adults worldwide. ADHD has a predominantly genetic aetiology that involves common and rare genetic variants. Some environmental correlates of the disorder have been discovered but causation has been difficult to establish. The heterogeneity of the condition is evident in the diverse presentation of symptoms and levels of impairment, the numerous co-occurring mental and physical conditions, the various domains of neurocognitive impairment, and extensive minor structural and functional brain differences. The diagnosis of ADHD is reliable and valid when evaluated with standard diagnostic criteria. Curative treatments for ADHD do not exist but evidence-based treatments substantially reduce symptoms and/or functional impairment. Medications are effective for core symptoms and are usually well tolerated. Some non-pharmacological treatments are valuable, especially for improving adaptive functioning. Clinical and neurobiological research is ongoing and could lead to the creation of personalized diagnostic and therapeutic approaches for this disorder.

Association of bisphenol A with cognitive functions and functionality in adult attention deficit hyperactivity disorder

BACKGROUND

Bisphenol A (BPA) has been linked to attention-deficit/hyperactivity disorder (ADHD) symptoms, but the effects on cognitive functions and functionality in adult ADHD have not been investigated. We investigated the associations between serum BPA with cognitive functions and functionality in adult ADHD patients.

METHODS

The levels of BPA were measured in 45 adult ADHD patients and 45 well-matched healty controls. The relationship between plastic exposure and BPA was also evaluated. Stroop test and Wisconsin Card Sorting Test were applied for neurocognitive evaluation and participants were compared in basic cognitive functions including planning, organization, abstraction, problem solving, strategy development, set shifting, cognitive flexibility, variants of attention, information processing speed, the ability to change perceptual setup and response under interference. Sheehan disability scale was applied for functionality. The association of BPA with test scores was analyzed statistically.

RESULTS

Serum BPA levels in adult ADHD patients were found to be significantly higher than in healthy controls. There was no relationship between plastic exposure and BPA levels. BPA levels showed a significant effect on functionality in terms of work field. There were significant differences between the groups in terms of cognitive functions. However, no significant correlation was found between BPA levels and cognitive functions.

CONCLUSIONS

BPA is associated with ADHD and affects functionality in the field of work, but larger-scale further studies are needed for its effect on cognitive functions.

[Birth conditions and attention deficit/hyperactivity disorders (ADHD) in adults in the Pelotas (Brazil) birth cohorts of 1982 and 1993]

This study evaluates the association of birth conditions with attention deficit/hyperactivity disorders (ADHD) in adults using data from two birth cohorts in the city of Pelotas Rio Grande do Sul State, Brazil. In 1982 and 1993 all births in the city were identified and have been prospectively monitored. In the follow-ups at 30 and 22 years of the 1982 (n = 3,574) and 1993 (n = 3,780) cohorts, respectively, participants were examined, and trained psychologists applied the Mini-International Neuropsychiatric Interview (M.I.N.I.). Those individuals who met the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) diagnostic criteria were defined as positive for ADHD. Poisson regression with robust variance adjustment was used to estimate the prevalence ratio (PR) adjusted for sex, maternal skin color, family income, maternal age, maternal schooling during pregnancy, maternal marital status, parity, and maternal smoking during pregnancy. The prevalence of adult ADHD was 4.4% and 4.5% in the 1982 and 1993 cohorts, respectively. The prevalence of ADHD was higher in those born with lower weight, but no linear trend was observed, and those born with weight between 3,000 and 3,499 grams (PR = 1.40; 95%CI: 1.05-1.86) had the highest risk. For gestational age, we observed an inversely proportional relationship for the presence of ADHD: preterm infants had a 33% higher risk (95%CI: 0.90-1.96) of being considered as having ADHD than those born at 39 or more weeks, but as the confidence interval included nullity, this association may have occurred at random. These results indicate that birth weight and gestational age may be associated with adult ADHD.

Identifying different patterns of emotion dysregulation in adult ADHD

BACKGROUND

Emotion dysregulation (ED) is a core intrinsic feature of adult presenting Attention Deficit Hyperactivity Disorder (ADHD). However, the clinical expressions of ED are diverse and several questionnaires have been used to measure ED in adults with ADHD. Thus, to date, the characteristics of ED in adult ADHD remain poorly defined. The objective of this study is to identify the different patterns of ED in adults with ADHD.

METHODS

A large sample of 460 newly diagnosed adults with ADHD were recruited. Patients completed a total of 20 self-reported questionnaires. Measures consisted in the several facets of ED, but also other clinical features of adult ADHD such as racing thoughts. A factor analysis with the principal component extraction method was performed to define the symptomatic clusters. A mono-dimensional clustering was then conducted to assess whether participants presented or not with each symptomatic cluster.

RESULTS

The factor analysis yielded a 5 factor-solution, including "emotional instability", "impulsivity", "overactivation", "inattention/disorganization" and "sleep problems". ED was part of two out of five clusters and concerned 67.52% of our sample. Among those patients, the combined ADHD presentation was the most prevalent. Emotional instability and impulsivity were significantly predicted by childhood maltreatment. The ED and the "sleep problems" factors contributed significantly to the patients' functional impairment.

CONCLUSIONS

ED in ADHD is characterized along emotional instability and emotional impulsivity, and significantly contributes to functional impairment. However, beyond impairing symptoms, adult ADHD may also be characterized by functional strengths such as creativity.

Neurogenetic mechanisms of risk for ADHD: Examining associations of polygenic scores and brain volumes in a population cohort

BACKGROUND

ADHD polygenic scores (PGSs) have been previously shown to predict ADHD outcomes in several studies. However, ADHD PGSs are typically correlated with ADHD but not necessarily reflective of causal mechanisms. More research is needed to elucidate the neurobiological mechanisms underlying ADHD. We leveraged functional annotation information into an ADHD PGS to (1) improve the prediction performance over a non-annotated ADHD PGS and (2) test whether volumetric variation in brain regions putatively associated with ADHD mediate the association between PGSs and ADHD outcomes.

METHODS

Data were from the Philadelphia Neurodevelopmental Cohort (N = 555). Multiple mediation models were tested to examine the indirect effects of two ADHD PGSs-one using a traditional computation involving clumping and thresholding and another using a functionally annotated approach (i.e., AnnoPred)-on ADHD inattention (IA) and hyperactivity-impulsivity (HI) symptoms, via gray matter volumes in the cingulate gyrus, angular gyrus, caudate, dorsolateral prefrontal cortex (DLPFC), and inferior temporal lobe.

RESULTS

A direct effect was detected between the AnnoPred ADHD PGS and IA symptoms in adolescents. No indirect effects via brain volumes were detected for either IA or HI symptoms. However, both ADHD PGSs were negatively associated with the DLPFC.

CONCLUSIONS

The AnnoPred ADHD PGS was a more developmentally specific predictor of adolescent IA symptoms compared to the traditional ADHD PGS. However, brain volumes did not mediate the effects of either a traditional or AnnoPred ADHD PGS on ADHD symptoms, suggesting that we may still be underpowered in clarifying brain-based biomarkers for ADHD using genetic measures.

The diagnosis and treatment of attention-deficit hyperactivity disorder (ADHD) in older adults

INTRODUCTION

There is a striking knowledge gap on ADHD in older adults, and the diagnosis as well as treatment for ADHD in this age group.

AREAS COVERED

The authors first review the literature on the prevalence, functional impairment, and health comorbidities of ADHD across the lifespan. Next, they address the diagnostic criteria for ADHD in adults according to the DSM/ICD, available screening/diagnostic tools, differential diagnosis, and the validity of diagnostic criteria for ADHD in older adults. Finally, the authors focus on empirical evidence on the prevalence rates, medication response, and safety of pharmacological treatment of ADHD in older adults, and national and international clinical guidelines on the treatment of ADHD in this age group.

EXPERT OPINION

It is expected that future editions of the DSM and ICD will provide specifiers to the standard ADHD criteria, to better inform the diagnosis of ADHD in older adults. It is also expected that the increasing number of epidemiological studies will provide rigorous estimates on the prevalence, incidence, and burden of ADHD in older adults. One may expect an increasing number of RCTs assessing the efficacy/effectiveness and tolerability/safety of pharmacological as well as non-pharmacological interventions which will inform future guidelines on ADHD in older adults.

Features of attention deficit/hyperactivity disorder and antisocial behaviour in a general population-based sample of adults

BACKGROUND

Attention deficit/hyperactivity disorder (ADHD) is known to be a risk factor for antisocial and delinquent behaviour, but there is still a lack of information on how features of ADHD relate to offending behaviour among adults not already defined by their offending.

AIMS

Our aim was to add to knowledge about relationships between ADHD and antisocial behaviour among adults in the general population by answering the following questions: (A) Does the level of self-reported ADHD features relate to criminal and non-criminal antisocial behaviour? (B) To what extent are self-ratings of ADHD features independent of socio-demographic features previously identified as predictors of antisocial behaviour?

METHODS

A sample of adults was originally recruited to study public response to the COVID-19 outbreak through an online panel to be representative of the Israeli population. Among other scales, the 2025 participants completed an ADHD self-report scale, an antisocial behaviour self-report scale and a socio-demographic questionnaire probing for age, gender, urbanity, place of birth, socioeconomic status (education and income), family status (being in a relationship and having children) and religiosity.

RESULTS

Higher mean totals for the inattention and hyperactivity ADHD scale scores were associated with higher mean antisocial behaviour scores. These relationships were only slightly affected by socio-demographic variables, including sex, age, education and income.

CONCLUSION

Our findings suggest that not only may features of ADHD, even below a diagnostic threshold, constitute a risk factor for antisocial behaviour, but also that the self-rated levels of these problems covary. These findings are important for informing the early detection of risk of antisocial behaviour in the general population and its prevention.

ADHD genetic burden associates with older epigenetic age: mediating roles of education, behavioral and sociodemographic factors among older adults

BACKGROUND

Shortened lifespans are associated with having Attention Deficit Hyperactivity Disorder (ADHD), which is likely mediated by related behavioral and sociodemographic factors that are also associated with accelerated physiological aging. Such factors include exhibiting more depressive symptoms, more cigarette smoking, higher body mass index, lower educational attainment, lower income in adulthood, and more challenges with cognitive processes compared to the general population. A higher polygenic score for ADHD (ADHD-PGS) is associated with having more characteristic features of ADHD. The degree to which (1) the ADHD-PGS associates with an epigenetic biomarker developed to predict accelerated aging and earlier mortality is unknown, as are whether (2) an association would be mediated by behavioral and sociodemographic correlates of ADHD, or (3) an association would be mediated first by educational attainment, then by behavioral and sociodemographic correlates. We evaluated these relationships in a population-based sample from the US Health and Retirement Study, among N = 2311 adults age 50 and older, of European-ancestry, with blood-based epigenetic and genetic data. The ADHD-PGS was calculated from a prior genomewide meta-analysis. Epigenome-wide DNA methylation levels that index biological aging and earlier age of mortality were quantified by a blood-based biomarker called GrimAge. We used a structural equation modeling approach to test associations with single and multi-mediation effects of behavioral and contextual indicators on GrimAge, adjusted for covariates.

RESULTS

The ADHD-PGS was significantly and directly associated with GrimAge when adjusting for covariates. In single mediation models, the effect of the ADHD-PGS on GrimAge was partially mediated via smoking, depressive symptoms, and education. In multi-mediation models, the effect of the ADHD-PGS on GrimAge was mediated first through education, then smoking, depressive symptoms, BMI, and income.

CONCLUSIONS

Findings have implications for geroscience research in elucidating lifecourse pathways through which ADHD genetic burden and symptoms can alter risks for accelerated aging and shortened lifespans, when indexed by an epigenetic biomarker. More education appears to play a central role in attenuating negative effects on epigenetic aging from behavioral and sociodemographic risk factors related to ADHD. We discuss implications for the potential behavioral and sociodemographic mediators that may attenuate negative biological system effects.

An overview on neurobiology and therapeutics of attention-deficit/hyperactivity disorder

Attention-Deficit/Hyperactivity Disorder (ADHD) is a prevalent psychiatric condition characterized by developmentally inappropriate symptoms of inattention and/or hyperactivity/impulsivity, which leads to impairments in the social, academic, and professional contexts. ADHD diagnosis relies solely on clinical assessment based on symptom evaluation and is sometimes challenging due to the substantial heterogeneity of the disorder in terms of clinical and pathophysiological aspects. Despite the difficulties imposed by the high complexity of ADHD etiology, the growing body of research and technological advances provide good perspectives for understanding the neurobiology of the disorder. Such knowledge is essential to refining diagnosis and identifying new therapeutic options to optimize treatment outcomes and associated impairments, leading to improvements in all domains of patient care. This review is intended to be an updated outline that addresses the etiological and neurobiological aspects of ADHD and its treatment, considering the impact of the "omics" era on disentangling the multifactorial architecture of ADHD.

Shared Genetic Factors Contributing to the Overlap between Attention-Deficit/Hyperactivity Disorder Symptoms and Overweight/Obesity in Swedish Adolescent Girls and Boys

Attention-deficit/hyperactivity disorder (ADHD) and obesity are positively associated, with increasing evidence that they share genetic risk factors. Our aim was to examine whether these findings apply to both types of ADHD symptoms for female and male adolescents. We used data from 791 girl and 735 boy twins ages 16-17 years to examine sex-specific phenotypic correlations between the presence of ADHD symptoms and overweight/obese status. For correlations exceeding .20, we then fit bivariate twin models to estimate the genetic and environmental correlations between the presence of ADHD symptoms and overweight/obese status. ADHD symptoms and height/weight were parent- and self-reported, respectively. Phenotypic correlations were .30 (girls) and .08 (boys) for inattention and overweight/obese status and .23 (girls) and .14 (boys) for hyperactivity/impulsivity and overweight/obese status. In girls, both types of ADHD symptoms and overweight/obese status were highly heritable, with unique environmental effects comprising the remaining variance. Furthermore, shared genetic effects explained most of the phenotypic correlations in girls. Results suggest that the positive association of both types of ADHD symptoms with obesity may be stronger in girls than boys. Further, in girls, these associations may stem primarily from shared genetic factors.

The Link between ADHD Symptoms and Antisocial Behavior: The Moderating Role of the Protective Factor Sense of Coherence

Numerous studies have established the link between ADHD and antisocial behavior, one of the most serious functional impairments caused by the disorder. However, research on protective factors that mitigate this link is still lacking. The Salutogenic Model of Health offers the “Sense of Coherence” (SOC), establishing that individuals who see their lives as logical, meaningful, and manageable are more resistant to various risk factors and diseases. The present study examines for the first time whether SOC is also a protective factor against different ADHD-related types of antisocial behaviors (severe/mild violent behavior, verbal violence, property crimes, public disorder, and drug abuse). A total of 3180 participants aged 15−50 completed online questionnaires assessing the level of ADHD symptoms, antisocial behaviors, and SOC. Structural equation modeling was applied to examine the research hypothesis. An interaction between ADHD symptoms and SOC was found in predicting each type of antisocial behavior (beta = −0.06−−0.17, p < 0.01). The link between ADHD symptoms and antisocial behavior was significantly weaker for high than low SOC participants, regardless of age group. The current study found that people with high SOC are protected against the effect of ADHD symptoms on one of the most serious functional impairments, antisocial behavior. These findings suggest that SOC is a protective factor from the adverse effects of ADHD symptoms, justifying further prospective and intervention studies.

The Transgender and Gender Diverse and Attention Deficit Hyperactivity Disorder Nexus: A Systematic Review

Introduction

Prior work suggests an increased prevalence of Attention Deficit Hyperactivity Disorder (ADHD) among transgender and/or gender diverse (TGD) individuals. This systematic review summarizes primary literature on TGD/ADHD experience.

Methods

Texts from databases, reference lists, and referral were screened per PRISMA guidelines, with author consensus.

Results

Since 2014, 17 articles have been published on the TGD/ADHD nexus. Gender-affirming care specialists authored 65%. 71% reported prevalence, per medical records. Only case reports discussed implications. None avoided deficit-framing, nor included explicit TGD/ADHD authorship.

Conclusions

The paucity of literature and lack of explicit TGD/ADHD community involvement are striking; each warrants increased attention.

Relevance of ω-6 GLA Added to ω-3 PUFAs Supplements for ADHD: A Narrative Review

The use of polyunsaturated fatty acids in Attention-Deficit/Hyperactivity Disorder (ADHD) and developmental disorders has been gaining interest with preparations containing different dosages and combinations. Gamma-linolenic acid (GLA) is an ω-6 fatty acid of emerging interest with potential roles as an adjuvant anti-inflammatory agent that could be used with ω-3 PUFAs in the treatment of ADHD and associated symptoms. A narrative review was undertaken to examine the potential role(s) of the ω-6 fatty acid GLA. PubMed, Google Scholar, and Scopus were searched to examine the potential role(s) of the ω-6 fatty acid GLA as (1) an antioxidant and anti-inflammatory agent, (2) a synergistic nutrient when combined with ω-3 PUFAs, and (3) a potential etiological factor in ADHD and its treatment. The results show that GLA exerts anti-inflammatory effects by increasing dihomo-gamma-linolenic acid in immune cells. ω-3 PUFAs, such as EPA and DHA, are often co-administered with GLA because these ω-3 PUFAs may prevent the accumulation of serum arachidonic acid in response to GLA administration without limiting the storage of DGLA in immune cells. The administration of ω-3 PUFAs alone might not be sufficient to effectively treat patients with ADHD and developmental disorders. Overall studies point towards a combination of EPA and DHA with GLA in a 9:3:1 ratio appearing to be associated with ADHD symptom improvement. A combination of PUFAs may lead to better outcomes.

Differences in the genetic architecture of common and rare variants in childhood, persistent and late-diagnosed attention-deficit hyperactivity disorder

Attention-deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder with onset in childhood (childhood ADHD); two-thirds of affected individuals continue to have ADHD in adulthood (persistent ADHD), and sometimes ADHD is diagnosed in adulthood (late-diagnosed ADHD). We evaluated genetic differences among childhood (n = 14,878), persistent (n = 1,473) and late-diagnosed (n = 6,961) ADHD cases alongside 38,303 controls, and rare variant differences in 7,650 ADHD cases and 8,649 controls. We identified four genome-wide significant loci for childhood ADHD and one for late-diagnosed ADHD. We found increased polygenic scores for ADHD in persistent ADHD compared with the other two groups. Childhood ADHD had higher genetic overlap with hyperactivity and autism compared with late-diagnosed ADHD and the highest burden of rare protein-truncating variants in evolutionarily constrained genes. Late-diagnosed ADHD had a larger genetic overlap with depression than childhood ADHD and no increased burden in rare protein-truncating variants. Overall, these results suggest a genetic influence on age at first ADHD diagnosis, persistence of ADHD and the different comorbidity patterns among the groups.

Global DNA methylation changes in adults with attention deficit-hyperactivity disorder and its comorbidity with bipolar disorder: links with polygenic scores

Genetic and environmental factors contribute to the etiology of Attention Deficit-Hyperactivity Disorder (ADHD). In this sense, the study of epigenetic mechanisms could contribute to the understanding of the disorder's neurobiology. Global DNA methylation (GMe) evaluated through 5-methylcytosine levels could be a promising epigenetic biomarker to capture long-lasting biological effects in response to environmental and hormonal changes. We conducted the first assessment of GMe levels in subjects with ADHD (n = 394) and its main comorbidities in comparison to populational controls (n = 390). Furthermore, given the high genetic contribution to ADHD (heritability of 80%), polygenic risk scores (PRS) were calculated to verify the genetic contribution to GMe levels in ADHD and the comorbidities associated with GMe levels. The GMe levels observed in patients were lower than controls (P = 1.1e-8), with women being significantly less globally methylated than men (P = 0.002). Regarding comorbidities, the presence of bipolar disorder (BD) among patients with ADHD was associated with higher methylation levels compared to patients with ADHD without BD (P = 0.031). The results did not change when pharmacological treatment was accounted for in the analyses. The ADHD and BD most predictive PRSs were negatively (P = 0.0064) and positively (P = 0.0042) correlated with GMe, respectively. This study is the first to report an association between GMe, ADHD, and its comorbidity with BD and associations between PRSs for specific psychiatric disorders and GMe. Our findings add to previous evidence that GMe may be a relevant piece in the psychiatric disorders' etiological landscape.

Genetics in the ADHD Clinic: How Can Genetic Testing Support the Current Clinical Practice?

Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder with a childhood prevalence of 5%. In about two-thirds of the cases, ADHD symptoms persist into adulthood and often cause significant functional impairment. Based on the results of family and twin studies, the estimated heritability of ADHD approximates 80%, suggests a significant genetic component in the etiological background of the disorder; however, the potential genetic effects on disease risk, symptom severity, and persistence are unclear. This article provides a brief review of the genome-wide and candidate gene association studies with a focus on the clinical aspects, summarizing findings of ADHD disease risk, ADHD core symptoms as dimensional traits, and other traits frequently associated with ADHD, which may contribute to the susceptibility to other comorbid psychiatric disorders. Furthermore, neuropsychological impairment and measures from neuroimaging and electrophysiological paradigms, emerging as potential biomarkers, also provide a prominent target for molecular genetic studies, since they lie in the pathway from genes to behavior; therefore, they can contribute to the understanding of the underlying neurobiological mechanisms and the interindividual heterogeneity of clinical symptoms. Beyond the aforementioned aspects, throughout the review, we also give a brief summary of the genetic results, including polygenic risk scores that can potentially predict individual response to different treatment options and may offer a possibility for personalized treatment for the therapy of ADHD in the future.

Predicting Children with ADHD Using Behavioral Activity: A Machine Learning Analysis

Attention deficit hyperactivity disorder (ADHD) is one of childhood’s most frequent neurobehavioral disorders. The purpose of this study is to: (i) extract the most prominent risk factors for children with ADHD; and (ii) propose a machine learning (ML)-based approach to classify children as either having ADHD or healthy. We extracted the data of 45,779 children aged 3–17 years from the 2018–2019 National Survey of Children’s Health (NSCH, 2018–2019). About 5218 (11.4%) of children were ADHD, and the rest of the children were healthy. Since the class label is highly imbalanced, we adopted a combination of oversampling and undersampling approaches to make a balanced class label. We adopted logistic regression (LR) to extract the significant factors for children with ADHD based on p-values (<0.05). Eight ML-based classifiers such as random forest (RF), Naïve Bayes (NB), decision tree (DT), XGBoost, k-nearest neighborhood (KNN), multilayer perceptron (MLP), support vector machine (SVM), and 1-dimensional convolution neural network (1D CNN) were adopted for the prediction of children with ADHD. The average age of the children with ADHD was 12.4 ± 3.4 years. Our findings showed that RF-based classifier provided the highest classification accuracy of 85.5%, sensitivity of 84.4%, specificity of 86.4%, and an AUC of 0.94. This study illustrated that LR with RF-based system could provide excellent accuracy for classifying and predicting children with ADHD. This system will be helpful for early detection and diagnosis of ADHD.

Accounting for age of onset and family history improves power in genome-wide association studies

Genome-wide association studies (GWASs) have revolutionized human genetics, allowing researchers to identify thousands of disease-related genes and possible drug targets. However, case-control status does not account for the fact that not all controls may have lived through their period of risk for the disorder of interest. This can be quantified by examining the age-of-onset distribution and the age of the controls or the age of onset for cases. The age-of-onset distribution may also depend on information such as sex and birth year. In addition, family history is not routinely included in the assessment of control status. Here, we present LT-FH++, an extension of the liability threshold model conditioned on family history (LT-FH), which jointly accounts for age of onset and sex as well as family history. Using simulations, we show that, when family history and the age-of-onset distribution are available, the proposed approach yields statistically significant power gains over LT-FH and large power gains over genome-wide association study by proxy (GWAX). We applied our method to four psychiatric disorders available in the iPSYCH data and to mortality in the UK Biobank and found 20 genome-wide significant associations with LT-FH++, compared to ten for LT-FH and eight for a standard case-control GWAS. As more genetic data with linked electronic health records become available to researchers, we expect methods that account for additional health information, such as LT-FH++, to become even more beneficial.

Genetic identification of tissues and cell types underlying attention-deficit/hyperactivity disorder

BACKGROUND

Genome-wide association studies (GWASs) have identified numerous genetic variants associated with attention-deficit/hyperactivity disorder (ADHD), which is considered highly genetically heritable. However, because most of the variants located in the non-coding region of the human genome, the onset of ADHD requires further exploration.

METHODS

The risk genes involved in ADHD were identified by integrating GWAS summary data and expression quantitative trait locus (eQTL) data using summary-data-based Mendelian randomization (SMR) method. We then used a stratified linkage disequilibrium score regression (LDSR) method to estimate the contribution of ADHD-relevant tissues to its heritability to screen out disease-relevant tissues. To determine the ADHD-relevant cell types, we used an R package for expression-weighted cell type enrichment (EWCE) analysis.

RESULTS

By integrating the brain eQTL data and ADHD GWAS data using SMR, we identified 247 genes associated with ADHD. The LDSR applied to specifically expressed genes results showed that the ADHD risk genes were mainly enriched in brain tissue, especially in the mesencephalon, visual cortex, and frontal lobe regions. Further cell-type-specific analysis suggested that ADHD risk genes were highly expressed in excitatory neurons.

CONCLUSION

The study showed that the etiology of ADHD is associated with excitatory neurons in the midbrain, visual cortex, and frontal lobe regions.

Gene-Environment Interactions in Attention-Deficit/Hyperactivity Disorder Symptom Dimensions: The Role of Unhealthy Food Habits

Background: Dietary habits were investigated as environmental risk factors for Attention-Deficit/Hyperactivity Disorder (ADHD). However, no previous studies explored the effects of dietary factors on modifying the role of genetic factors on ADHD. Methods: Based on a Swedish population-based twin study with 1518 twin pairs aged 20-47 years, we tested whether the importance of genetic and environmental effects on ADHD varied as a function of dietary habits. Self-reported dietary habits and ADHD symptoms were collected. Twin methods were used to test the degree to which high-sugar and unhealthy food intake moderated the genetic and environmental influences on ADHD symptoms. Results: In middle-aged adults, genetic influences on inattention symptoms were statistically significantly higher among individuals with higher levels of high-sugar (45%, 95%CI: 25-54%) and unhealthy food intake (51%, 95%CI: 31-60%), compared with those with lower levels of consumption of high-sugar (36%, 95%CI: 25-47%) and unhealthy foods (30%, 95%CI: 20-41%). Similar patterns were also found for the associations between hyperactivity/impulsivity and high-sugar/unhealthy food intake, even though the moderation effects were not statistically significant. Conclusion The present study suggests that genetic factors play a more prominent role in individual differences of ADHD symptoms in the presence of the high consumption of sugar and unhealthy foods. Future longitudinal studies with multiple assessments of ADHD and dietary habits are needed to replicate our findings.

Insights into attention-deficit/hyperactivity disorder from recent genetic studies

Attention-deficit/hyperactivity disorder (ADHD) is a common and highly heritable neurodevelopmental disorder (NDD). In this narrative review, we summarize recent advances in quantitative and molecular genetic research from the past 5-10 years. Combined with large-scale international collaboration, these advances have resulted in fast-paced progress in understanding the etiology of ADHD and how genetic risk factors map on to clinical heterogeneity. Studies are converging on a number of key insights. First, ADHD is a highly polygenic NDD with a complex genetic architecture encompassing risk variants across the spectrum of allelic frequencies, which are implicated in neurobiological processes. Second, genetic studies strongly suggest that ADHD diagnosis shares a large proportion of genetic risks with continuously distributed traits of ADHD in the population, with shared genetic risks also seen across development and sex. Third, ADHD genetic risks are shared with those implicated in many other neurodevelopmental, psychiatric and somatic phenotypes. As sample sizes and the diversity of genetic studies continue to increase through international collaborative efforts, we anticipate further success with gene discovery, characterization of how the ADHD phenotype relates to other human traits and growing potential to use genomic risk factors for understanding clinical trajectories and for precision medicine approaches.

Elevated risk of attention deficit hyperactivity disorder (ADHD) in Japanese children with higher genetic susceptibility to ADHD with a birth weight under 2000 g

BACKGROUND

Both genetic and pre- and perinatal factors, including birth weight, have been implicated in the onset of attention deficit hyperactivity disorder (ADHD) traits among children. This study aimed to elucidate to what extent the genetic risk of ADHD moderates the association between birth weight and ADHD traits among Japanese children.

METHODS

We conducted a longitudinal birth cohort study (Hamamatsu Birth Cohort for Mother and Children Study) to investigate the association of genetic risk for ADHD and low birth weight with ADHD traits among Japanese children. Out of 1258 children, we included 796 who completed follow-ups at 8 to 9 years of age. Birth weight was categorized as <2000 g, 2000-2499 g, and ≥2500 g. Polygenic risk score for ADHD was generated using the summary data of a large-scale genome-wide association study. The Rating Scale IV (ADHD-RS) assessed ADHD traits (inattention and hyperactivity/impulsivity) based on parental reports. Following previous studies, sex, birth order of the child, gestational age at birth, mother's age at delivery, educational attainment, pre-pregnancy body mass index, pre-pregnancy or during pregnancy smoking status, alcohol consumption during pregnancy, father's age, education, and annual family income were considered as covariates. Multivariable negative binomial regression was applied to evaluate the association between birth weight and ADHD traits, while adjusting for potential covariates. The interaction term between birth weight categories and binary polygenic risk was added to the model.

RESULTS

Birth weight of 2000-2499 g was not associated with ADHD traits. Birth weight under 2000 g was significantly associated with both inattention and hyperactivity. When accounting for higher and lower genetic risk for ADHD, only those with higher genetic risk and birth weight < 2000 g were associated with inattention (rate ratio [RR] 1.56, 95% CI 1.07-2.27) and hyperactivity (RR 1.87, 95% CI 1.14-3.06).

CONCLUSIONS

Birth weight under 2000 g, together with the genetic risk of ADHD, contributes to higher levels of ADHD traits among Japanese children aged 8 to 9 years. The suggested association between low birth weight and ADHD is confined to children with a genetic susceptibility to ADHD, indicating the relevance of genetic-environmental interactions in the etiology.

Borderline personality disorder (BPD) and attention deficit hyperactivity disorder (ADHD) revisited - a review-update on common grounds and subtle distinctions

BACKGROUND

Overlap in symptom domains particularly in the field of impulsivity and emotional dysregulation in attention deficit hyperactivity disorder (ADHD) and borderline personality disorder (BPD) have stimulated further research activities since our last review from 2014.

MAIN BODY

Disentangling features of impulsivity in ADHD and BPD revealed that impulsivity is a feature of both disorders with patients suffering from both ADHD and BPD having highest impulsivity ratings. BPD individuals have more problems using context cues for inhibiting responses and their impulsivity is stress-dependent, whereas ADHD patients have more motor impulsivity and therefore difficulties interrupting ongoing responses. For emotion regulation difficulties the ranking order ranges from ADHD to BPD to the comorbid condition, again with the patients suffering from both, ADHD and BPD, having the most pronounced emotion regulation problems. Environmental influences namely adverse childhood events were shown to be linked to both ADHD and BPD. Traumatic experiences seem independently linked to impulsivity features. Thus, some authors point to the risk of misdiagnosis during childhood and the necessity to screen for traumatic experiences in both patient groups. Genetic research confirmed genetic overlap of BPD with bipolar disorder (BD) and schizophrenic disorders, as well as genetic overlap of BD and ADHD. A population-based study confirmed the high co-occurrence and familial co-aggregation of ADHD and BPD. Interesting questions in the field of gene-environment-interactions are currently dealt with by genetic and epigenetic research. Few studies have investigated treatment strategies for the comorbid condition, though the issue is highly important for the management of patients suffering from both disorders and presenting with the highest symptom scores.

CONCLUSION

Research on the different impulsivity features might point to a necessity of disorder-specific treatment strategies in the field of impulse control. Future research is needed to base treatment decisions for the comorbid condition on an evidence basis.

Behavioral and cognitive functioning in individuals with Cantú syndrome

Cantú syndrome (CS) is caused by pathogenic variants in ABCC9 and KCNJ8 encoding the regulatory and pore-forming subunits of ATP-sensitive potassium (K_ATP ) channels. CS is characterized by congenital hypertrichosis, distinctive facial features, peripheral edema, and cardiac and neurodevelopmental abnormalities. Behavioral and cognitive issues have been self-reported by some CS individuals, but results of formal standardized investigations have not been published. To assess the cognitive profile, social functioning, and psychiatric symptoms in a large group of CS subjects systematically in a cross-sectional manner, we invited 35 individuals (1-69 years) with confirmed ABCC9 variants and their relatives to complete various commonly applied standardized age-related questionnaires, including the Kaufman brief intelligence test 2, the social responsiveness scale-2, and the Achenbach system of empirically based assessment. The majority of CS individuals demonstrated average verbal and nonverbal intelligence compared to the general population. Fifteen percent of cases showed social functioning strongly associated with a clinical diagnosis of autism spectrum disorder. Both externalizing and internalizing problems were also present in this cohort. In particular, anxiety, anxiety or attention deficit hyperactivity disorder, and autism spectrum behaviors were predominantly observed in the younger subjects in the cohort (≥25%), but this percentage decreased markedly in adults.

Integrating genomics and transcriptomics: Towards deciphering ADHD

Attention-deficit/hyperactivity disorder (ADHD) is a highly heritable condition that represents the most common neurodevelopmental disorder in childhood, persisting into adulthood in around 40-65% of the cases. ADHD is characterised by age-inappropriate symptoms of inattention, impulsivity, and hyperactivity. Mounting evidence points towards ADHD having a strong genetic component and the first genome-wide significant findings have recently been reported. However, the functional characterization of variants unravelled by genome-wide association studies (GWAS) is challenging. Likewise, gene expression profiling studies have also been undertaken and novel integrative approaches combining genomic and transcriptomic data are starting to be conducted, which offers an exciting way that might provide a more informative insight towards the genetic architecture of ADHD. In this review, we summarised current knowledge on genomics, transcriptomics and integrative approaches in ADHD, focusing on GWAS and GWAS meta-analyses (GWAS-MA)- as genomics analyses- microarray and RNA-seq- as transcriptomics analyses-, and studies integrating genomics and transcriptomics data. In addition, current strengths and limitations of such approaches are discussed and further research avenues are proposed in order to face unsolved issues. Although important progress has been made, there is still a long way ahead to elucidate the biological mechanisms of ADHD, which eventually may lead to more personalized approaches in the future. Large- scale research efforts and new technological and statistical approaches are envisaged as important means towards deciphering ADHD in the upcoming years.

Maternal ADHD medication use during pregnancy and the risk of ADHD in children: Importance of genetic predispositions and impact of using a sibling analysis

Attention deficit with hyperactivity disorder (ADHD) medications in pregnancy would be associated with ADHD in children, however, estimates can be confounded by genetic predispositions and environmental factors related to the mother-child pair. We aim to quantify the risk of ADHD in children associated with ADHD medication exposures during pregnancy. A prospective cohort study and sibling analysis conducted within The Quebec Pregnancy/Child Cohort (QPC). All full-term singleton live births covered by the provincial prescription drug insurance in Quebec from 1998 to 2015 were included. ADHD medication exposure during pregnancy was defined according to trimester of use and class-specific medication. ADHD in children was defined as having at least one diagnosis or one prescription filled for an ADHD medication. Cox proportional hazards regression models were used to calculate crude and adjusted hazard ratios (aHR) with 95% confidence intervals (CIs) in the overall cohort, the sub-cohort and the sibling analysis. Of 166,047 full-term singleton live births included, 25,454 (15.3%) had ADHD. In the overall cohort, maternal exposure to ADHD medication during pregnancy was associated with ADHD in children (aHR= 1.96, 95% CI 1.22-3.15). In the ADHD pregnant women sub-cohort (aHR= 1.56; 95% CI 0.93-2.62) and the sibling control analysis (aHR= 1.14; 95% CI 0.62-1.98), ADHD medications during pregnancy was not associated with an increased risk of ADHD in children. Our findings suggest that in utero exposure to ADHD medications was not associated with an increased risk of ADHD in children. This suggests that the association is due to genetic and/or family environmental factors.

A population-based family clustering study of tic-related obsessive-compulsive disorder

In the latest edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), obsessive-compulsive disorder (OCD) included a new "tic-related" specifier. However, strong evidence supporting tic-related OCD as a distinct subtype of OCD is lacking. This study investigated whether, at the population level, tic-related OCD has a stronger familial load than non-tic-related OCD. From a cohort of individuals born in Sweden between 1967 and 2007 (n = 4,085,367; 1257 with tic-related OCD and 20,975 with non-tic-related OCD), we identified all twins, full siblings, maternal and paternal half siblings, and cousins. Sex- and birth year-adjusted hazard ratios (aHR) were calculated to estimate the risk of OCD in relatives of individuals with OCD with and without comorbid tics, compared with relatives of unaffected individuals. We found that OCD is a familial disorder, regardless of comorbid tic disorder status. However, the risk of OCD in relatives of individuals with tic-related OCD was considerably greater than the risk of OCD in relatives of individuals with non-tic-related OCD (e.g., risk for full siblings: aHR = 10.63 [95% CI, 7.92-14.27] and aHR = 4.52 [95% CI, 4.06-5.02], respectively; p value for the difference < 0.0001). These differences remained when the groups were matched by age at first OCD diagnosis and after various sensitivity analyses. The observed familial patterns of OCD in relation to tics were not seen in relation to other neuropsychiatric comorbidities. Tic-related OCD is a particularly familial subtype of OCD. The results have important implications for ongoing gene-searching efforts.

Do borderline personality disorder and attention-deficit/hyperactivity disorder co-aggregate in families? A population-based study of 2 million Swedes

Large-scale family studies on the co-occurrence of attention-deficit/hyperactivity disorder (ADHD) and borderline personality disorder (BPD) are lacking. Thus, we aimed to estimate the co-occurrence and familial co-aggregation of clinically ascertained ADHD and BPD diagnoses using the entire Swedish population. In a register-based cohort design we included individuals born in Sweden 1979-2001, and identified their diagnoses during 1997-2013; in total, 2,113,902 individuals were included in the analyses. We obtained clinical diagnoses of ADHD and BPD from inpatient and outpatient care. Individuals with an ADHD diagnosis had an adjusted (for birth year, sex, and birth order) odds ratio (aOR) of 19.4 (95% confidence interval [95% CI] = 18.6-20.4) of also having a BPD diagnosis, compared to individuals not diagnosed with ADHD. Having a sibling with ADHD also increased the risk for BPD (monozygotic twins, aOR = 11.2, 95% CI = 3.0-42.2; full siblings, aOR = 2.8, 95% CI = 2.6-3.1; maternal half-siblings, aOR = 1.4, 95% CI = 1.2-1.7; paternal half-siblings, aOR = 1.5, 95% CI = 1.3-1.7). Cousins also had an increased risk. The strength of the association between ADHD and BPD was similar in females and males, and full siblings showed similar increased risks regardless of sex. Among both males and females, ADHD and BPD co-occur within individuals and co-aggregate in relatives; the pattern suggests shared genetic factors and no robust evidence for etiologic sex differences was found. Clinicians should be aware of increased risks for BPD in individuals with ADHD and their relatives, and vice versa.

Association between Maternal Adverse Childhood Experiences and Attention-Deficit/Hyperactivity Disorder in the Offspring: The Mediating Role of Antepartum Health Risks

Objectives

This study aimed to examine the effect of maternal adverse childhood experiences (ACEs) on the attention-deficit/hyper-activity disorder (ADHD) symptoms in the offspring and to examine the mediating role of antepartum health risk on the intergenera-tional transmission of maternal ACEs.

Methods

The participants consisted of 461 mother-child dyads. Mothers completed the ACEs questionnaire and Diagnostic Predictive Scales. Multivariate logistic regression analysis was used to estimate the risk of ADHD symptoms in the offspring of mothers with ACEs and the mediating effect of antepartum health risks by path analysis.

Results

In all, 35.4% (n=163) had at least one maternal ACE, and 11.1% (n=51) had three or more. Compared to the non-ADHD symp-tom group, the group of offspring with ADHD symptoms showed a significant association with maternal ACE score (p<0.001) and an-tepartum health risks (p<0.001). Multivariate analysis further showed a significant association between the sum of maternal ACEs [odds ratio (OR)=1.264, 95% confidence interval (CI)= 1.060–1.516, p=0.009], antepartum health risks (OR=1.236, 95% CI=1.036–1.475, p= 0.019), and ADHD symptoms in the offspring. In the mediation model in which the mother’s ACE score affected the offspring’s ADHD symptoms, partial mediation through antepartum health risks was found to be significant (B=0.041, 95% CI=0.011–0.124).

Conclusion

Maternal ACEs are significantly related to the incidence of ADHD symptoms in the offspring and antepartum health risks exert an indirect effect. These findings suggest that maternal ACEs have a negative impact on the offspring’s brain development through intergenerational transmission, resulting in neurodevelopmental disorders such as ADHD.

Energy Metabolism Disturbances in Cell Models of PARK2 CNV Carriers with ADHD

The main goal of the present study was the identification of cellular phenotypes in attention-deficit-/hyperactivity disorder (ADHD) patient-derived cellular models from carriers of rare copy number variants (CNVs) in the PARK2 locus that have been previously associated with ADHD. Human-derived fibroblasts (HDF) were cultured and human-induced pluripotent stem cells (hiPSC) were reprogrammed and differentiated into dopaminergic neuronal cells (mDANs). A series of assays in baseline condition and in different stress paradigms (nutrient deprivation, carbonyl cyanide m-chlorophenyl hydrazine (CCCP)) focusing on mitochondrial function and energy metabolism (ATP production, basal oxygen consumption rates, reactive oxygen species (ROS) abundance) were performed and changes in mitochondrial network morphology evaluated. We found changes in PARK2 CNV deletion and duplication carriers with ADHD in PARK2 gene and protein expression, ATP production and basal oxygen consumption rates compared to healthy and ADHD wildtype control cell lines, partly differing between HDF and mDANs and to some extent enhanced in stress paradigms. The generation of ROS was not influenced by the genotype. Our preliminary work suggests an energy impairment in HDF and mDAN cells of PARK2 CNV deletion and duplication carriers with ADHD. The energy impairment could be associated with the role of PARK2 dysregulation in mitochondrial dynamics.

Attention-deficit/hyperactivity disorder symptoms and dietary habits in adulthood: A large population-based twin study in Sweden

Associations between adult attention-deficit/hyperactivity disorder (ADHD) symptoms and dietary habits have not been well established and the underlying mechanisms remain unclear. We explored these associations using a Swedish population-based twin study with 17,999 individuals aged 20-47 years. We estimated correlations between inattention and hyperactivity/impulsivity with dietary habits and fitted twin models to determine the genetic and environmental contributions. Dietary habits were defined as (a) consumption of food groups, (b) consumption of food items rich in particular macronutrients, and (c) healthy and unhealthy dietary patterns. At the phenotypic level, inattention was positively correlated with seafood, high-fat, high-sugar, high-protein food consumptions, and unhealthy dietary pattern, with correlation coefficients ranging from 0.03 (95%CI: 0.01, 0.05) to 0.13 (95% CI: 0.11, 0.15). Inattention was negatively correlated with fruits, vegetables consumptions and healthy dietary pattern, with correlation coefficients ranging from -0.06 (95%CI: -0.08, -0.04) to -0.07 (95%CI: -0.09, -0.05). Hyperactivity/impulsivity and dietary habits showed similar but weaker patterns compared to inattention. All associations remained stable across age, sex and socioeconomic status. Nonshared environmental effects contributed substantially to the correlations of inattention (56-60%) and hyperactivity/impulsivity (63-80%) with dietary habits. The highest and lowest genetic correlations were between inattention and high-sugar food (r_A = .16, 95% CI: 0.07, 0.25), and between hyperactivity/impulsivity and unhealthy dietary pattern (r_A = .05, 95% CI: -0.05, 0.14), respectively. We found phenotypic and etiological overlap between ADHD and dietary habits, although these associations were weak. Our findings contribute to a better understanding of common etiological pathways between ADHD symptoms and various dietary habits.

Visual exogenous and endogenous attention and visual memory in preschool children who stutter

PURPOSE

Attention develops gradually from infancy to the preschool years and beyond. Exogenous attention, consisting of automatic responses to salient stimuli, develops in infancy, whereas endogenous attention, or voluntary attention, begins to develop later, in the preschool years. The purpose of this study was to examine (a) exogenous and endogenous attention in young children who stutter (CWS) and children who do not stutter (CWNS) through two conditions of a visual sustained selective attention task, and (b) visual short-term memory (STM) between groups within the context of this task.

METHOD

42 CWS and 42 CWNS, ages 3;0-5;5 (years;months), were pair-matched in age, gender (31 males, 11 females per group), and socioeconomic status. Children completed a visual tracking task (Track-It Task; Fisher et al., 2013) requiring sustained selective attention and engaging exogenous and endogenous processes. Following each item, children were asked to recall the item they had tracked, as a memory check.

RESULTS

The CWS group demonstrated significantly less accuracy in overall tracking and visual memory for the tracked stimuli, compared to the CWNS group. Across groups, the children performed better in sustained selective attention when the target stimuli were more salient (the condition tapping both exogenous and endogenous attention) than when stimuli were less so (the condition tapping primarily endogenous processes).

CONCLUSIONS

Relative to peers, preschool-age CWS, as a group, display weaknesses in visual sustained selective attention and visual STM.

Research Review: The strength of the genetic overlap between ADHD and other psychiatric symptoms - a systematic review and meta-analysis

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) frequently co-occurs with other psychiatric disorders. Twin studies have established that these co-occurrences are in part due to shared genetic risks. However, the strength of these genetic overlaps and the potential heterogeneity accounted for by type of psychiatric symptoms, age, and methods of assessment remain unclear. We conducted a systematic review to fill this gap.

METHODS

We searched PubMed, PsycINFO, Embase, and Web of Science until March 07, 2019. Genetic correlations (r_g ) were used as effect size measures.

RESULTS

A total of 31 independent studies fulfilled the inclusion criteria. The pooled estimates showed that the associations between ADHD and other psychiatric symptoms were partly explained by shared genetic factors, with a pooled genetic correlation of 0.50, 95% confidence interval: 0.46-0.60. The genetic correlations (r_g ) between ADHD and externalizing (r_g  = .49 [0.37-0.61]), internalizing (r_g  = .50 [0.39-0.69]), and neurodevelopmental (r_g  = .56 [0.47-0.66]) symptoms were similar in magnitude. The genetic correlations in childhood and adulthood were r_g  = .53 (0.43-0.63) and r_g  = .51 (0.44-0.56), respectively. For methods of assessment, the genetic correlations were also similar in strength, self-reports r_g  = .52 (0.47-0.58), other informants r_g  = .55 (0.41-0.69), and combined raters r_g  = .50 (0.33-0.65).

CONCLUSIONS

These findings indicate that the co-occurrence of externalizing, internalizing, and neurodevelopmental disorder symptoms in individuals with ADHD symptoms in part is due to a shared genetic risk.

Brain Network Connectivity and Association with Catechol-O-Methyltransferase Gene Polymorphism in Korean Attention-Deficit Hyperactivity Disorder Children

OBJECTIVE

We sought to determine if the links between and within the default mode network (DMN) and dorsal attention network (DAT) exhibited different conditions according to catechol-O-methyltransferase (COMT) gene polymorphism in relationship to attention-deficit hyperactivity disorder (ADHD) symptoms.

METHODS

Fifty-seven children with ADHD and 48 healthy controls (HCs) were administered an intelligence test, the Children's Depression Inventory, the Korean ADHD rating scale, and continuous performance test. Resting-state brain functional MRI scans were obtained, and COMT genotyping was performed to distinguish valine carriers and methionine homozygotes.

RESULTS

Compared to controls, children with ADHD showed increased ADHD scale scores, increased visual commission errors, and increased functional connectivity (FC) within the DMN and DAT. Compared to all children with ADHD, children with the methionine homozygote and those who were valine carriers showed increased FC within the DMN and DAT and decreased FC between the DMN and DAT. FC within the DMN was also increased in HC valine carriers compared to HC children with the methionine homozygote, and in children with ADHD who were valine carriers compared to HC valine carriers.

CONCLUSION

We observed increased brain connectivity within the DMN and DAT and altered brain connectivity within and between the DMN and DAT associated with COMT polymorphism in children with ADHD.

Shared genetic background between children and adults with attention deficit/hyperactivity disorder

Attention deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder characterized by age-inappropriate symptoms of inattention, impulsivity, and hyperactivity that persist into adulthood in the majority of the diagnosed children. Despite several risk factors during childhood predicting the persistence of ADHD symptoms into adulthood, the genetic architecture underlying the trajectory of ADHD over time is still unclear. We set out to study the contribution of common genetic variants to the risk for ADHD across the lifespan by conducting meta-analyses of genome-wide association studies on persistent ADHD in adults and ADHD in childhood separately and jointly, and by comparing the genetic background between them in a total sample of 17,149 cases and 32,411 controls. Our results show nine new independent loci and support a shared contribution of common genetic variants to ADHD in children and adults. No subgroup heterogeneity was observed among children, while this group consists of future remitting and persistent individuals. We report similar patterns of genetic correlation of ADHD with other ADHD-related datasets and different traits and disorders among adults, children, and when combining both groups. These findings confirm that persistent ADHD in adults is a neurodevelopmental disorder and extend the existing hypothesis of a shared genetic architecture underlying ADHD and different traits to a lifespan perspective.

The contribution of common genetic risk variants for ADHD to a general factor of childhood psychopathology

Common genetic risk variants have been implicated in the etiology of clinical attention-deficit/hyperactivity disorder (ADHD) diagnoses and symptoms in the general population. However, given the extensive comorbidity across ADHD and other psychiatric conditions, the extent to which genetic variants associated with ADHD also influence broader psychopathology dimensions remains unclear. The aim of this study was to evaluate the associations between ADHD polygenic risk scores (PRS) and a broad range of childhood psychiatric symptoms, and to quantify the extent to which such associations can be attributed to a general factor of childhood psychopathology. We derived ADHD PRS for 13,457 children aged 9 or 12 from the Child and Adolescent Twin Study in Sweden, using results from an independent meta-analysis of genome-wide association studies of ADHD diagnosis and symptoms. We estimated associations between ADHD PRS, a general psychopathology factor, and several dimensions of neurodevelopmental, externalizing, and internalizing symptoms, using structural equation modeling. Higher ADHD PRS were statistically significantly associated with elevated neurodevelopmental, externalizing, and depressive symptoms (R2 = 0.26-1.69%), but not with anxiety. After accounting for a general psychopathology factor, on which all symptoms loaded positively (mean loading = 0.50, range = 0.09-0.91), an association with specific hyperactivity/impulsivity remained significant. ADHD PRS explained ~ 1% (p value < 0.0001) of the variance in the general psychopathology factor and ~ 0.50% (p value < 0.0001) in specific hyperactivity/impulsivity. Our results suggest that common genetic risk variants associated with ADHD, and captured by PRS, also influence a general genetic liability towards broad childhood psychopathology in the general population, in addition to a specific association with hyperactivity/impulsivity symptoms.

Clinical versus automated assessments of morphological variants in twins with and without neurodevelopmental disorders

Physical examinations are recommended as part of a comprehensive evaluation for individuals with neurodevelopmental disorders (NDDs), such as autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder. These examinations should include assessment for morphological variants. Previous studies have shown an increase in morphological variants in individuals with NDDs, particularly ASD, and that these variants may be present in greater amounts in individuals with genetic alterations. Unfortunately, assessment for morphological variants can be subjective and time-consuming, and require a high degree of clinical expertise. Therefore, objective, automated methods of morphological assessment are desirable. This study compared the use of Face2Gene, an automated tool to explore facial morphological variants, to clinical consensus assessment, using a cohort of N = 290 twins enriched for NDDs (n = 135 with NDD diagnoses). Agreement between automated and clinical assessments were satisfactory to complete (78.3-100%). In our twin sample, individuals with NDDs did not have greater numbers of facial morphological variants when compared to those with typical development, nor when controlling for shared genetic and environmental factors within twin pairs. Common facial morphological variants in those with and without NDDs were similar and included thick upper lip vermilion, abnormality of the nasal tip, long face, and upslanted palpebral fissure. We conclude that although facial morphological variants can be assessed reliably in NDDs with automated tools like Face2Gene, clinical utility is limited when just exploring the facial region. Therefore, currently, automated assessments may best complement, rather than replace, in-person clinical assessments.

EEG spectral power, but not theta/beta ratio, is a neuromarker for adult ADHD

Adults with attention-deficit/hyperactivity disorder (ADHD) have been described as having altered resting-state electroencephalographic (EEG) spectral power and theta/beta ratio (TBR). However, a recent review (Pulini et al. 2018) identified methodological errors in neuroimaging, including EEG, ADHD classification studies. Therefore, the specific EEG neuromarkers of adult ADHD remain to be identified, as do the EEG characteristics that mediate between genes and behaviour (mediational endophenotypes). Resting-state eyes-open and eyes-closed EEG was measured from 38 adults with ADHD, 45 first-degree relatives of people with ADHD and 51 unrelated controls. A machine learning classification analysis using penalized logistic regression (Elastic Net) examined if EEG spectral power (1-45 Hz) and TBR could classify participants into ADHD, first-degree relatives and/or control groups. Random-label permutation was used to quantify any bias in the analysis. Eyes-open absolute and relative EEG power distinguished ADHD from control participants (area under receiver operating characteristic = 0.71-0.77). The best predictors of ADHD status were increased power in delta, theta and low-alpha over centro-parietal regions, and in frontal low-beta and parietal mid-beta. TBR did not successfully classify ADHD status. Elevated eyes-open power in delta, theta, low-alpha and low-beta distinguished first-degree relatives from controls (area under receiver operating characteristic = 0.68-0.72), suggesting that these features may be a mediational endophenotype for adult ADHD. Resting-state EEG spectral power may be a neuromarker and mediational endophenotype of adult ADHD. These results did not support TBR as a diagnostic neuromarker for ADHD. It is possible that TBR is a characteristic of childhood ADHD.

Development of the Korean Practice Parameter for Adult Attention-Deficit/Hyperactivity Disorder

OBJECTIVES

Adult attention-deficit/hyperactivity disorder (ADHD) is an important mental health problem that needs resolution, especially considering the high rates of ADHD continuation from childhood to adolescence/adulthood and the high prevalence of ADHD in adults. Adults with ADHD have lifelong negative impacts and require close monitoring with long-term follow-up. Hence, the establishment of a Korean practice parameter for adult ADHD is necessary to minimize discontinuation of treatment and enable information sharing among Korean mental health professionals.

METHODS

The Korean practice parameter was developed using an evidence-based approach consisting of expert consensus survey coupled with literature review.

RESULTS

According to the expert consensus survey, the most commonly used diagnostic methods were clinical psychiatric interview (20.66%) and self-report scales (19.25%) followed by attention (14.71%) and psychological tests (14.24%). Key evaluation instruments currently available in Korea are the World Health Organization Adult ADHD Self-Report Rating Scale, Korean Adult ADHD Rating Scale, Diagnostic Interview for ADHD in Adults, Barkley Deficits in Executive Functioning Scale for adults, Comprehensive Attention Test, Conners' Continuous Performance Test, and the subtests of Wechsler Adult Intelligence Scale, Digit Span and Letter-Number Sequencing. Although pharmacotherapy is recommended as the first-line of treatment for adult ADHD, we recommend that it be followed by a multimodal and multidisciplinary approach including psychoeducation, pharmacotherapy, cognitive behavior therapy and coaching.

CONCLUSION

The Korean practice parameter introduces not only general information for the diagnosis and treatment of adult ADHD on a global scale, but also the process of diagnosis and treatment options tailored to the Korean population.

Antibiotic Exposure in the First Year of Life and the Risk of Attention-Deficit/Hyperactivity Disorder: A Population-Based Cohort Study

Early childhood antibiotic exposure induces changes in gut microbiota reportedly associated with the development of attention-deficit/hyperactivity disorder (ADHD). We conducted a population-based cohort study to examine the association between antibiotic use in the first year of life and ADHD risk. We included children born in Manitoba, Canada, between 1998 and 2017. Exposure was defined as having filled 1 or more antibiotic prescriptions during the first year of life. ADHD diagnosis was identified in hospital abstracts, physician visits, or drug dispensations. Risk of developing ADHD was estimated using Cox proportional hazards regression in a high-dimensional propensity score-matched cohort (n = 69,738) and a sibling cohort (n = 67,671). ADHD risk was not associated with antibiotic exposure in the matched-cohort (hazard ratio = 1.02, 95% confidence interval: 0.97, 1.08) or in the sibling cohort (hazard ratio = 0.96, 95% confidence interval: 0.89, 1.03). In secondary analyses of the matched cohort, ADHD risk increase was observed in those exposed to 4 or more antibiotic courses or a duration longer than 3 weeks. These associations were not observed in the sibling cohort. We concluded that antibiotic exposure in the first year of life does not pose an ADHD risk on a population level.

Prenatal maternal stress and risk of neurodevelopmental disorders in the offspring: a systematic review and meta-analysis

PURPOSE

Exposure to prenatal stress has been reported to affect the risk of adverse neurodevelopmental outcomes in the offspring; however, there is currently no clear consensus. The aim of this systematic review and meta-analysis was to examine the existing literature on the association between prenatal stress and autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD) in the offspring.

METHODS

Based on a registered protocol, we searched several electronic databases for articles in accordance with a detailed search strategy. We performed this study following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA).

RESULTS

Prenatal stress was significantly associated with an increased risk of both ASD (pooled OR 1.64 [95% CI 1.15-2.34]; I² = 90%; 15 articles) and ADHD (pooled OR 1.72 [95% CI 1.27-2.34]; I² = 85%; 12 articles).

CONCLUSIONS

This study suggests that prenatal stress may be associated with ASD and ADHD; however, several limitations in the reviewed literature should be noted including significant heterogeneity and there is a need for carefully controlled future studies in this area.

Dynamical properties of elemental metabolism distinguish attention deficit hyperactivity disorder from autism spectrum disorder

Attention deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) are neurodevelopmental conditions of overlapping etiologies and phenotypes. For ASD, we recently reported altered elemental metabolic patterns in the form of short and irregular zinc and copper cycles. Here, we extend the application of these biomarkers of prenatal and early postnatal elemental metabolism to distinguish between individuals diagnosed with ADHD and/or ASD and neurotypical controls. We recruited twins discordant for ADHD, ASD and other neurodevelopmental diagnoses from national twin studies in Sweden (N = 74) diagnosed according to DSM-5 clinical consensus and standardized psychiatric instruments. Detailed temporal profiles of exposure to 10 metals over the prenatal and early childhood periods were measured using tooth biomarkers. We used recurrence quantification analysis (RQA) to characterize properties of cyclical metabolic patterns of these metals. Regularity (determinism) and complexity (entropy) of elemental cycles was consistently reduced in ADHD for cobalt, lead, and vanadium (determinism: cobalt, β = -0.03, P = 0.017; lead, β = -0.03, P = 0.016; and vanadium, β = -0.03, P = 0.01. Entropy: cobalt, β = -0.13, P = 0.017; lead, β = -0.18, P = 0.016; and vanadium, β = -0.15, P = 0.008). Further, we found elemental pathways and dynamical features specific to ADHD vs ASD, and unique characteristics associated with ADHD/ASD combined presentation. Dysregulation of cyclical processes in elemental metabolism during prenatal and early postnatal development not only encompasses pathways shared by ADHD and ASD, but also comprise features specific to either condition.

Functional EEG connectivity is a neuromarker for adult attention deficit hyperactivity disorder symptoms

OBJECTIVE

Altered brain functional connectivity has been shown in youth with attention-deficit/hyperactivity disorder (ADHD). However, relatively little is known about functional connectivity in adult ADHD, and how it is linked with the heritability of ADHD.

METHODS

We measured eyes-open and eyes-closed resting electroencephalography (EEG) from 38 adults with ADHD, 45 1st degree relatives of people with ADHD and 51 healthy controls. Functional connectivity among all scalp channels was calculated using a weighted phase lag index for delta, theta, alpha, beta and gamma frequency bands. A machine learning analysis using penalized linear regression was used to identify if connectivity features (10,080 connectivity pairs) could predict ADHD symptoms. Furthermore, we examined if EEG connectivity could accurately classify participants into ADHD, 1st degree relatives and/or control groups.

RESULTS

Hyperactive symptoms were best predicted by eyes-open EEG connectivity in delta, beta and gamma bands. Inattentive symptoms were predicted by eyes-open EEG connectivity in delta, alpha and gamma bands, and eyes-closed EEG connectivity in delta and gamma bands. EEG connectivity features did not reliably classify participants into groups.

CONCLUSIONS

EEG connectivity may represent a neuromarker for ADHD symptoms.

SIGNIFICANCE

EEG connectivity may help elucidate the neural basis of adult ADHD symptoms.

Psychiatric Polygenic Risk Scores as Predictor for Attention Deficit/Hyperactivity Disorder and Autism Spectrum Disorder in a Clinical Child and Adolescent Sample

Neurodevelopmental disorders such as attention deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) are highly heritable and influenced by many single nucleotide polymorphisms (SNPs). SNPs can be used to calculate individual polygenic risk scores (PRS) for a disorder. We aim to explore the association between the PRS for ADHD, ASD and for Schizophrenia (SCZ), and ADHD and ASD diagnoses in a clinical child and adolescent population. Based on the most recent genome wide association studies of ADHD, ASD and SCZ, PRS of each disorder were calculated for individuals of a clinical child and adolescent target sample (N = 688) and for adult controls (N = 943). We tested with logistic regression analyses for an association with (1) a single diagnosis of ADHD (N = 280), (2) a single diagnosis of ASD (N = 295), and (3) combining the two diagnoses, thus subjects with either ASD, ADHD or both (N = 688). Our results showed a significant association of the ADHD PRS with ADHD status (OR 1.6, P = 1.39 × 10⁻⁰⁷) and with the combined ADHD/ASD status (OR 1.36, P = 1.211 × 10⁻⁰⁵), but not with ASD status (OR 1.14, P = 1). No associations for the ASD and SCZ PRS were observed. In sum, the PRS of ADHD is significantly associated with the combined ADHD/ASD status. Yet, this association is primarily driven by ADHD status, suggesting disorder specific genetic effects of the ADHD PRS.

Maternal smoking during pregnancy and physiological anxiety in children with attention deficit hyperactivity disorder

Our objective was to explore the relationship between mother smoking during pregnancy and physiological anxiety of children with Attention deficit-hyperactivity disorder. Cognitive profile was evaluated by Wechsler Intelligence Scale for Children, physiological anxiety by Children's Manifest Anxiety Scale. Mother's smoking was evaluated by the Fagerström test for nicotine dependence. Ninety-seven children with Attention Deficit-Hyperactivity Disorder combined type, 70 inattentive, and 48 hyperactive-impulsive, and 130 controls were studied. We found a higher frequency of high smoking dependence in mothers of children with Attention Deficit-Hyperactivity Disorder-combined type, and Attention Deficit Hyperactivity Disorder-hyperactive type in the Fagerström test; and a significant correlation between physiological anxiety in children with Attention Deficit Hyperactivity Disorder-combined type, with high and moderate maternal smoking level during pregnancy. In conclusion, data suggests, with caution a brain alteration of infants, induced by nicotine exposure during pregnancy in children with Attention Deficit Hyperactivity Disorder-combined type, and Attention Deficit Hyperactivity Disorder-hyperactive type.

Genetic and environmental contribution to the overlap between ADHD and ASD trait dimensions in young adults: a twin study

BACKGROUND

Traits of attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) are strongly associated in children and adolescents, largely due to genetic factors. Less is known about the phenotypic and aetiological overlap between ADHD and ASD traits in adults.

METHODS

We studied 6866 individuals aged 20-28 years from the Swedish Study of Young Adult Twins. Inattention (IA) and hyperactivity/impulsivity (HI) were assessed using the WHO Adult ADHD Self-Report Scale-V1.1. Repetitive and restricted behaviours (RRB) and social interaction and communication (SIC) were assessed using the Autism-Tics, ADHD, and other Comorbidities inventory. We used structural equation modelling to decompose covariance between these ADHD and ASD trait dimensions into genetic and shared/non-shared environmental components.

RESULTS

At the phenotypic level, IA was similarly correlated with RRB (r = 0.33; 95% Confidence Interval (CI) 0.31-0.36) and with SIC (r = 0.32; 95% CI 0.29-0.34), whereas HI was more strongly associated with RRB (r = 0.38; 95% CI 0.35-0.40) than with SIC (r = 0.24; 95% CI 0.21-0.26). Genetic and non-shared environmental effects accounted for similar proportions of the phenotypic correlations, whereas shared environmental effects were of minimal importance. The highest genetic correlation was between HI and RRB (r = 0.56; 95% 0.46-0.65), and the lowest was between HI and SIC (r = 0.33; 95% CI 0.23-0.43).

CONCLUSIONS

We found evidence for dimension-specific phenotypic and aetiological overlap between ADHD and ASD traits in adults. Future studies investigating mechanisms underlying comorbidity between ADHD and ASD may benefit from exploring several symptom-dimensions, rather than considering only broad diagnostic categories.

Neuroinflammation as a risk factor for attention deficit hyperactivity disorder

Attention Deficit Hyperactivity Disorder (ADHD) is a persistent, and impairing pediatric-onset neurodevelopmental condition. Its high prevalence, and recurrent controversy over its widespread identification and treatment, drive strong interest in its etiology and mechanisms. Emerging evidence for a role for neuroinflammation in ADHD pathophysiology is of great interest. This evidence includes 1) the above-chance comorbidity of ADHD with inflammatory and autoimmune disorders, 2) initial studies indicating an association with ADHD and increased serum cytokines, 3) preliminary evidence from genetic studies demonstrating associations between polymorphisms in genes associated with inflammatory pathways and ADHD, 4) emerging evidence that early life exposure to environmental factors may increase risk for ADHD via an inflammatory mechanism, and 5) mechanistic evidence from animal models of maternal immune activation documenting behavioral and neural outcomes consistent with ADHD. Prenatal exposure to inflammation is associated with changes in offspring brain development including reductions in cortical gray matter volume and the volume of certain cortical areas -parallel to observations associated with ADHD. Alterations in neurotransmitter systems, including the dopaminergic, serotonergic and glutamatergic systems, are observed in ADHD populations. Animal models provide strong evidence that development and function of these neurotransmitters systems are sensitive to exposure to in utero inflammation. In summary, accumulating evidence from human studies and animal models, while still incomplete, support a potential role for neuroinflammation in the pathophysiology of ADHD. Confirmation of this association and the underlying mechanisms have become valuable targets for research. If confirmed, such a picture may be important in opening new intervention routes.

Genetics of attention deficit hyperactivity disorder

Decades of research show that genes play an vital role in the etiology of attention deficit hyperactivity disorder (ADHD) and its comorbidity with other disorders. Family, twin, and adoption studies show that ADHD runs in families. ADHD's high heritability of 74% motivated the search for ADHD susceptibility genes. Genetic linkage studies show that the effects of DNA risk variants on ADHD must, individually, be very small. Genome-wide association studies (GWAS) have implicated several genetic loci at the genome-wide level of statistical significance. These studies also show that about a third of ADHD's heritability is due to a polygenic component comprising many common variants each having small effects. From studies of copy number variants we have also learned that the rare insertions or deletions account for part of ADHD's heritability. These findings have implicated new biological pathways that may eventually have implications for treatment development.