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

Exploring voice as a digital phenotype in adults with ADHD

Current diagnostic procedures for attention deficit hyperactivity disorder (ADHD) are mainly subjective and prone to bias. While research on potential biomarkers, including EEG, brain imaging, and genetics is promising, it has yet to demonstrate clinical utility. Dopaminergic signaling alternations and executive functioning, crucial to ADHD pathology, are closely related to voice production. Consistently, previous studies point to alterations in voice and speech production in ADHD. However, studies investigating voice in large clinical samples allowing for individual-level prediction of ADHD are lacking. Here, 387 ADHD patients, 204 healthy controls, and 100 psychiatric controls underwent standardized diagnostic assessment. Subjects provided multiple 3-minutes speech samples, yielding 920 samples. Based on prosodic voice features, random forest-based classifications were performed, and cross-validated out-of-sample accuracy was calculated. The classification of ADHD showed the best performance in young female participants (AUC = 0.87) with lower performance in older participants and males. Psychiatric comorbidity did not alter the classification performance. Voice features were associated with ADHD-symptom severity as indicated by random forest regressions. In summary, prosodic features seem to be promising candidates for further research into voice-based digital phenotypes of ADHD.

Gene-level connections between anxiety disorders, ADHD, and head and neck cancer: insights from a computational biology approach

Background

Anxiety disorders (AD), ADHD, and head and neck cancer (HNC) are complex conditions with potential genetic interconnections that remain to be fully elucidated. The purpose of this study is to investigate gene-level connections among ADHD, AD, and HNC.

Method

A comprehensive literature mining approach identified potential gene-disease relationships from PubMed and bioinformatics databases, analyzing 19,924 genes. An AI-driven computational process constructed a gene-disease relationship table using the Adjusted Binomial Method Algorithm (ABMA) to evaluate association reliability. Overlapping genes were analyzed through protein-protein interaction (PPI) networks, functional annotations, and literature-based pathway analyses to elucidate shared and unique genetic mechanisms linking these diseases.

Results

The analysis identified 141 significant genes associated with AD, 153 with ADHD, and 1,065 with HNC (q-value < 0.05). These genes demonstrated significant overlap (odds ratio ≥ 1.8; p ≤ 2.58E-2) and high interconnectivity (PPI network density ≥ 0.39, clustering coefficient ≥ 0.76, and diameter ≤ 3). Centrality analysis revealed core genes such as IL-6, MYC, NLRP3, and CXCR4 as critical mediators. Functional enrichment analysis identified key pathways, including serotonergic synapse, inflammatory response, and Toll-like receptor signaling, highlighting the involvement of neuronal and immune mechanisms. Functional pathway analysis demonstrated reciprocal genetic influences among AD, ADHD, and HNC, emphasizing shared and distinct gene-level connections that may underlie their co-occurrence and mutual risk factors.

Conclusion

This study reveals a complex and interconnected genetic network among AD, ADHD, and HNC, highlighting shared pathways, unique mechanisms, and critical genes, providing valuable insights into the genetic underpinnings of these conditions and potential avenues for therapeutic exploration.

Setting a research agenda for examining early risk for elevated cognitive disengagement syndrome symptoms using data from the ABCD cohort

Little research has examined early life risk for symptoms of cognitive disengagement syndrome (CDS) despite a well-established literature regarding co-occurring outcomes (e.g., attention-deficit/hyperactivity disorder). The current study estimated bivariate associations between early life risk factors and CDS in a large and representative sample of U.S. children. We conducted secondary analyses of baseline data from the Adolescent Brain Cognitive Development (ABCD) study (N = 8,096 children, 9-10 years old). Birthing parents reported early life risk factors on a developmental history questionnaire, including parental, prenatal, delivery and birth, and developmental milestone information. They also completed the Child Behavior Checklist, which includes a CDS subscale that was dichotomized to estimate the odds of elevated CDS symptoms (i.e., T-score > 70) in children related to risk indices. We observed significantly elevated odds of CDS related to parental risk factors (i.e., unplanned pregnancy, pregnancy awareness after 6 weeks, teenage parenthood), birthing parent illnesses in pregnancy (i.e., severe nausea, proteinuria, pre-eclampsia/toxemia, severe anemia, urinary tract infection), pregnancy complications (i.e., bleeding), prenatal substance exposures (i.e., prescription medication, tobacco, illicit drugs), delivery and birth risk factors (i.e., child blue at delivery, child not breathing, jaundice, incubation after delivery), and late motor and speech milestones in children. Several early-life risk factors were associated with elevated odds of CDS at ages 9-10 years; study design prevents the determination of causality. Further investigation is warranted regarding early life origins of CDS with priority given to risk indices that have upstream commonalities (i.e., that restrict fetal growth, nutrients, and oxygen).

Simple Executive Function as an endophenotype of autism-ADHD, and differing associations between simple versus complex Executive Functions and autism/ADHD traits

Autism and ADHD are associated with difficulties with Executive Functions (EFs), but the prevalence and nature of these difficulties in early development is not well understood. In this longitudinal study, 107 children with a family history of autism and/or ADHD (FH-autism/ADHD), and 24 children with No-FH-autism/ADHD completed multiple EF tasks (5 at age 2 years, 7 at age 3 years). Parents reported on their child's autism- (Q-CHAT at age 2, SRS-2 at age 3), and ADHD-related traits (CBCL DSM-ADHD scale, both ages). Compared to the No-FH-autism/ADHD group, the FH-autism/ADHD group showed lower scores on simple EFs (involving response inhibition, and holding in mind) at ages 2 and 3. Exploratory analysis linked FH-autism specifically with lower Executive Attention (top-down attentional control) at age 2, and the combination of FH-autism and FH-ADHD with lower Complex EF (involving selectively deploying responses, or updating information) at age 3. Three-year-olds' Simple EF scores were negatively associated with ADHD-related traits. Complex EF scores were negatively associated with autism traits (before correcting for multiple comparisons). Toddlers with a family history of autism and/or ADHD may benefit from interventions to support simple EF development, whilst those already showing autistic traits may benefit from support with more-complex EF skills.

Genetic neurodevelopmental clustering and dyslexia

Dyslexia is a learning difficulty with neurodevelopmental origins, manifesting as reduced accuracy and speed in reading and spelling. It is substantially heritable and frequently co-occurs with other neurodevelopmental conditions, particularly attention deficit-hyperactivity disorder (ADHD). Here, we investigate the genetic structure underlying dyslexia and a range of psychiatric traits using results from genome-wide association studies of dyslexia, ADHD, autism, anorexia nervosa, anxiety, bipolar disorder, major depressive disorder, obsessive compulsive disorder, schizophrenia, and Tourette syndrome. Genomic Structural Equation Modelling (GenomicSEM) showed heightened support for a model consisting of five correlated latent genomic factors described as: F1) compulsive disorders (including obsessive-compulsive disorder, anorexia nervosa, Tourette syndrome), F2) psychotic disorders (including bipolar disorder, schizophrenia), F3) internalising disorders (including anxiety disorder, major depressive disorder), F4) neurodevelopmental traits (including autism, ADHD), and F5) attention and learning difficulties (including ADHD, dyslexia). ADHD loaded more strongly on the attention and learning difficulties latent factor (F5) than on the neurodevelopmental traits latent factor (F4). The attention and learning difficulties latent factor (F5) was positively correlated with internalising disorders (.40), neurodevelopmental traits (.25) and psychotic disorders (.17) latent factors, and negatively correlated with the compulsive disorders (-.16) latent factor. These factor correlations are mirrored in genetic correlations observed between the attention and learning difficulties latent factor and other cognitive, psychological and wellbeing traits. We further investigated genetic variants underlying both dyslexia and ADHD, which implicated 49 loci (40 not previously found in GWAS of the individual traits) mapping to 174 genes (121 not found in GWAS of individual traits) as potential pleiotropic variants. Our study confirms the increased genetic relation between dyslexia and ADHD versus other psychiatric traits and uncovers novel pleiotropic variants affecting both traits. In future, analyses including additional co-occurring traits such as dyscalculia and dyspraxia will allow a clearer definition of the attention and learning difficulties latent factor, yielding further insights into factor structure and pleiotropic effects.

Using Bifactor Twin Modeling to Assess the Genetic and Environmental Dimensionality of Adult ADHD Symptoms

Attention Deficit Hyperactivity Disorder (ADHD) is a common and heritable neurodevelopmental condition that has been the subject of a wealth of genetics research. Because ADHD has an early age of onset, most of this work has focused on children, meaning that less is known about the genetics of ADHD in adults. Additionally, while much research has assessed the heritability of ADHD as a general dimension, less has assessed the heritability of individual subtypes (inattention, hyperactivity) or symptoms of ADHD. It therefore remains unclear whether the genetic factors underlying ADHD symptoms conform to a unidimensional or multidimensional structure. The aim of this study was to assess the genetic and environmental dimensionality of adult ADHD symptoms. We analyzed data from 10,454 twins of the Twins Early Development Study, who provided self-reports of ADHD symptoms using the Conners scale at age 21 years. The data conformed well to a psychometric bifactor model, providing support for a general dimension of ADHD in addition to secondary dimensions for inattention and hyperactivity. However, a bifactor independent pathway twin model provided support for a general dimension only at the level of non-shared environmental effects and not additive genetic or shared environmental effects. This suggests that symptoms of ADHD cluster together under a general dimension of non-shared environmental effects, although the two subtypes of ADHD (inattention and hyperactivity) are meaningfully genetically distinct. We found the overall heritability of ADHD to be 40%, comparable with previous estimates for adult ADHD symptoms. Our results provide useful insights into the genetic and environmental architecture of specific ADHD symptoms.

Attitudes of parents of children with ADHD towards genetic testing: Data from a Turkish sample

This study aimed to examine the opinions of parents with children diagnosed with attention deficit/hyperactivity disorder about genetic tests. A total of 540 parents living in Turkey participated in the study face-to-face and online. A questionnaire form prepared by the researchers was used as the data collection instrument. Face-to-face data were collected in different institutions in the cities of İzmir, Bursa and Antalya, while online data were collected through Google Forms. The results revealed that parents' views on genetic testing differed according to the sex and age of the child, as well as the parents' level of education and income, and whether the parents had genetic testing during pregnancy (p < 0.05). In the analysis, it was determined that parents' knowledge and awareness levels about genetic tests were generally low, while parents who reported that they would consider having genetic tests had concerns about the storage of their DNA materials, family conflicts that could be caused by genetic tests, and the compatibility of genetic tests with their religious beliefs.

Executive function deficits in attention-deficit/hyperactivity disorder and autism spectrum disorder

Executive function deficits have been reported in both autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD). However, little is known regarding which, if any, of these impairments are unique vs. shared in children with ADHD versus ASD. In this Review, we provide an overview of the current literature with a critical eye toward diagnostic, measurement, and third-variable considerations that should be leveraged to provide more definitive answers. We conclude that the field's understanding of ASD and ADHD executive function profiles is highly limited because most research on one disorder has failed to account for their co-occurrence and the presence of symptoms of the other disorder; a vast majority of studies have relied on traditional neuropsychological tests and/or informant-rated executive function scales that have poor specificity and construct validity; and most studies have been unable to account for the well-documented between-person heterogeneity within and across disorders. Currently, the most parsimonious conclusion is that children with ADHD and/or ASD tend to perform moderately worse than neurotypical children on a broad range of neuropsychological tests. However, the extent to which these difficulties are unique vs. shared, or attributable to impairments in specific executive functions subcomponents, remains largely unknown. We end with focused recommendations for future research that we believe will advance this important line of inquiry.

Somatic burden of attention-deficit/hyperactivity disorder across the lifecourse

OBJECTIVE

A thorough and comprehensive knowledge base on the extent of comorbidity of attention-deficit/hyperactivity disorder (ADHD) and somatic conditions is needed.

METHOD

We compared the prevalence of a wide range of somatic conditions in individuals with and without ADHD and described sex and lifecourse differences. Individuals with an ADHD diagnosis (N = 87,394) and age and sex-matched individuals without an ADHD diagnosis were identified from a large health claims dataset representative of the general German population, including both primary and specialized care (N = 4.874,754). Results were provided for the full sample as well as stratified for sex and age (<12 years, 13-17 years, 18-29 years, 30-59 years, ≥60 years).

RESULTS

The results showed that ADHD is associated with a wide variety of somatic conditions across the entire lifecourse. Specifically neurological disorders such as Parkison's disease (odds ratio [OR]: 5.21) and dementia (OR: 2.23), sleep-related disorders (OR: 2.38) and autoimmune disorders affecting the musculoskeletal, digestive, and endocrine system (fibromyalgia OR: 3.33; lupus OR: 2.17) are strongly and significantly associated with ADHD. Additionally, ADHD is associated with higher occurrence of common acute diseases typically treated by the general practitioner, hinting at an overall general lower health status. Sex differences in somatic comorbidity were not prominent. Age differences, in contrast, stood out: in particular endocrine, cardiovascular, and neurological disorders had an early onset in individuals with compared to individuals without ADHD.

CONCLUSION

This research underlines the high burden of disease due to somatic conditions among individuals with ADHD. The findings indicate the need for preventive measures to reduce comorbidity.

Setting a research agenda for examining early risk for elevated cognitive disengagement syndrome symptoms using data from the ABCD cohort

Background

Little research has examined early life risk for symptoms of cognitive disengagement syndrome (CDS) despite a well-established literature regarding co-occurring outcomes (e.g., attention-deficit/hyperactivity disorder). The current study estimated bivariate associations between early life risk factors and CDS in a large and representative sample of U.S. children.

Methods

We conducted secondary analyses of baseline data from the Adolescent Brain Cognitive Development (ABCD) study (N = 8,096 children, 9-10 years old). Birthing parents reported early life risk factors on a developmental history questionnaire, including parental, prenatal, delivery and birth, and developmental milestone information. They also completed the Child Behavior Checklist, which includes a CDS subscale that was dichotomized to estimate the odds of elevated CDS symptoms (i.e., T-score > 70) in children related to risk indices.

Results

We observed significantly elevated odds of CDS related to parental risk factors (i.e., unplanned pregnancy, pregnancy awareness after 6 weeks, teenage parenthood), birthing parent illnesses in pregnancy (i.e., severe nausea, proteinuria, pre-eclampsia/toxemia, severe anemia, urinary tract infection), pregnancy complications (i.e., bleeding), prenatal substance exposures (i.e., prescription medication, tobacco, illicit drugs), delivery and birth risk factors (i.e., child blue at delivery, child not breathing, jaundice, incubation after delivery), and late motor and speech milestones in children.

Conclusions

Several early-life risk factors were associated with elevated odds of CDS at ages 9-10 years; study design prevents the determination of causality. Further investigation is warranted regarding early life origins of CDS with priority given to risk indices that have upstream commonalities (i.e., that restrict fetal growth, nutrients, and oxygen).

Criminal convictions in males and females diagnosed with attention deficit hyperactivity disorder: A Swedish national registry study

Background

Individuals with Attention-Deficit/Hyperactivity Disorder (ADHD) face an elevated risk of criminal convictions compared to those without ADHD. However, understanding this link involves considering sex differences, coexisting psychiatric conditions, and unmeasured familial factors. This study aimed to explore the connection between ADHD and criminal convictions (both violent and non-violent) in males and females, while also assessing the impact of comorbid psychiatric disorders and familial factors.

Methods

Using Swedish national registers, we identified individuals born between 1986 and 1997 (635,391 males and 600,548 females). ADHD was defined through clinical diagnosis and prescribed medications, while criminal convictions were determined based on Swedish lower court records. Unmeasured familial factors were accounted for using a sibling design approach.

Results

Findings revealed that individuals with ADHD had a notably higher absolute and relative risk of both violent and non-violent criminal convictions compared to those without ADHD. While criminal convictions were more frequent among males with ADHD, females with ADHD exhibited higher relative risks (HR violent 10.50, non-violent 4.04) than their male counterparts (HR violent 6.03, non-violent 3.57). Additionally, lower socioeconomic status (SES) in individuals with ADHD was associated with increased relative risks for criminal convictions compared to individuals with ADHD who had higher SES. Adjusting for childhood and internalizing psychiatric disorders partially attenuated these associations, while substance use disorders (SUD) substantially attenuated them. SUD also contributed to an elevated absolute risk of criminal convictions in both male and female individuals with ADHD. Accounting for unmeasured shared familial factors slightly reduced the estimates, but the association between ADHD and criminal convictions persisted.

Conclusion

In conclusion, ADHD remains a potent independent risk factor for criminal convictions, with varying effects based on gender. This underscores the importance of tailored crime prevention strategies and early interventions for individuals with ADHD, especially when comorbid SUD is present.

Identifying subgroups of attention-deficit/hyperactivity disorder from the psychopathological and neuropsychological profiles

The Research Domain Criteria (RDoC) advocates the dimensional approach in characterizing mental disorders. We followed RDoC to characterize children with ADHD using profiling based on the cognitive and psychopathological domains. We aimed to identify and validate ADHD subtypes with different clinical characteristics and functional impairments. We recruited 362 drug-naïve children with ADHD and 103 typically developing controls. The cluster analysis was used to identify subgroups based on the Child Behaviour Checklist (CBCL) and the Behaviour Rating Inventory of Executive Function (BRIEF). The subgroups' clinical characteristics and functional impairments were assessed using the WEISS Functional Impairment Rating Scale-Parent Report (WFIRS-P) and the Conners Parent Symptom Questionnaire (PSQ). The cluster analysis yielded four subgroups: (1) ADHD with severe impairment in psychopathology and executive functions (EF), (2) ADHD with mild executive dysfunctions and normal-level psychopathology, (3) ADHD with severe externalizing problems and (4) ADHD with severe executive dysfunctions. These subgroups showed different clinical characteristics and degrees of functional impairment. The EF impairment group displayed more serious learning problems and worse life skills than the externalizing group. The two groups with externalizing problems (i.e. the severe impairment group and the externalizing group) both exhibited higher rates of the combined subtype of ADHD and higher rates of comorbid ODD. Different subtypes of ADHD displayed different profiles of internalizing and externalizing problems and levels of executive dysfunctions. In particular, the subtype with severe impairment in EF exhibited more learning problems and worse life skills, suggesting EF is a critical target for intervention in children with ADHD.

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.

Genetic architecture of ADHD and overlap with other psychiatric disorders and cognition-related phenotypes

Attention-deficit/hyperactivity disorder (ADHD) co-occurs with many other psychiatric disorders and traits. In this review, we summarize and interpret the existing literature on the genetic architecture of these comorbidities based on hypothesis-generating approaches. Quantitative genetic studies indicate that genetic factors play a substantial role in the observed co-occurrence of ADHD with many different disorders and traits. Molecular genetic correlations derived from genome-wide association studies and results of studies based on polygenic risk scores confirm the general pattern but provide effect estimates that are smaller than those from twin studies. The identification of the specific genetic variants and biological pathways underlying co-occurrence using genome-wide approaches is still in its infancy. The first analyses of causal inference using genetic data support causal relationships between ADHD and comorbid disorders, although bidirectional effects identified in some instances point to complex relationships. While several issues in the methodology and inferences from the results are still to be overcome, this review shows that the co-occurrence of ADHD with many psychiatric disorders and traits is genetically interpretable.

Investigating heterogeneity across autism, ADHD, and typical development using measures of cortical thickness, surface area, cortical/subcortical volume, and structural covariance

Introduction

Attention-deficit/hyperactivity disorder (ADHD) and autism are multi-faceted neurodevelopmental conditions with limited biological markers. The clinical diagnoses of autism and ADHD are based on behavioural assessments and may not predict long-term outcomes or response to interventions and supports. To address this gap, data-driven methods can be used to discover groups of individuals with shared biological patterns.

Methods

In this study, we investigated measures derived from cortical/subcortical volume, surface area, cortical thickness, and structural covariance investigated of 565 participants with diagnoses of autism [n = 262, median(IQR) age = 12.2(5.9), 22% female], and ADHD [n = 171, median(IQR) age = 11.1(4.0), 21% female] as well neurotypical children [n = 132, median(IQR) age = 12.1(6.7), 43% female]. We integrated cortical thickness, surface area, and cortical/subcortical volume, with a measure of single-participant structural covariance using a graph neural network approach.

Results

Our findings suggest two large clusters, which differed in measures of adaptive functioning (χ 2 = 7.8, P = 0.004), inattention (χ 2 = 11.169, P < 0.001), hyperactivity (χ 2 = 18.44, P < 0.001), IQ (χ 2 = 9.24, P = 0.002), age (χ 2 = 70.87, P < 0.001), and sex (χ 2 = 105.6, P < 0.001).

Discussion

These clusters did not align with existing diagnostic labels, suggesting that brain structure is more likely to be associated with differences in adaptive functioning, IQ, and ADHD features.

The student-teacher relationship and ADHD symptomatology: A meta-analysis

Children with attention-deficit/hyperactivity disorder (ADHD) typically experience significant academic and social impairments, including problem behaviors in the classroom. Existing research suggests students who present with ADHD symptoms are more likely to have relationships with their teachers that are low in closeness and high in conflict. However, research about the quality of relationships between teachers and students with ADHD symptoms remains quantitatively un-synthesized. The present meta-analysis quantitatively describes the overall quality of student-teacher relationships for children who present with ADHD symptoms according to the relational dimensions of closeness and conflict. Database searches of PsycInfo, ERIC, and ProQuest (theses and dissertations) were conducted to collect a sample of 27 quantitative studies for statistical analyses. A total of 47 effect sizes (N = 17,236) were included in the analyses. Results confirm the trends seen in the literature. Children with symptoms of ADHD tended to have relationships with their teachers that were low in closeness (r = -0.170) and high in conflict (r = 0.414). Additionally, eight moderator analyses were conducted (i.e., grade level, informant types, informant consistency, sample type, reported comorbidity, gender, and ADHD presentation) to assess their effect on the link between ADHD symptoms and student-teacher relationship quality. The results of this meta-analysis provide insight into the quality of relationships that students who exhibit ADHD symptoms form with their teachers also may inform intervention programs that aim to best support students.

Do Children With Attention-Deficit/Hyperactivity Disorder Symptoms Become Socially Isolated? Longitudinal Within-Person Associations in a Nationally Representative Cohort

Objective

This study examined longitudinal associations between attention-deficit/hyperactivity disorder (ADHD) symptoms and social isolation across childhood. The study tested the direction of this association across time, while accounting for preexisting characteristics, and assessed whether this association varied by ADHD presentation, informant, sex, and socioeconomic status.

Method

Participants included 2,232 children from the Environmental Risk (E-Risk) Longitudinal Twin Study. ADHD symptoms and social isolation were measured at ages 5, 7, 10, and 12. Random-intercept cross-lagged panel models were used to assess the directionality of the association across childhood.

Results

Children with increased ADHD symptoms were consistently at increased risk of becoming socially isolated later in childhood, over and above stable characteristics (β = .05-.08). These longitudinal associations were not bidirectional; isolated children were not at risk of worsening ADHD symptoms later on. Children with hyperactive ADHD presentation were more likely to become isolated, compared with inattentive presentation. This was evident in the school setting, as observed by teachers, but not by mothers at home.

Conclusion

The study findings highlight the importance of enhancing peer social support and inclusion for children with ADHD, particularly in school settings. This study adds explanatory value beyond traditional longitudinal methods, as the results represent how individual children change over time, relative to their own preexisting characteristics.

Diversity & Inclusion Statement

We worked to ensure sex and gender balance in the recruitment of human participants. We worked to ensure that the study questionnaires were prepared in an inclusive way. One or more of the authors of this paper self-identifies as a member of one or more historically underrepresented sexual and/or gender groups in science. We actively worked to promote sex and gender balance in our author group. The author list of this paper includes contributors from the location and/or community where the research was conducted who participated in the data collection, design, analysis, and/or interpretation of the work.

A meta-analysis of genetic effects associated with neurodevelopmental disorders and co-occurring conditions

A systematic understanding of the aetiology of neurodevelopmental disorders (NDDs) and their co-occurrence with other conditions during childhood and adolescence remains incomplete. In the current meta-analysis, we synthesized the literature on (1) the contribution of genetic and environmental factors to NDDs, (2) the genetic and environmental overlap between different NDDs, and (3) the co-occurrence between NDDs and disruptive, impulse control and conduct disorders (DICCs). Searches were conducted across three platforms: Web of Science, Ovid Medline and Ovid Embase. Studies were included only if 75% or more of the sample consisted of children and/or adolescents and the studies had measured the aetiology of NDDs and DICCs using single-generation family designs or genomic methods. Studies that had selected participants on the basis of unrelated diagnoses or injuries were excluded. We performed multilevel, random-effects meta-analyses on 296 independent studies, including over four million (partly overlapping) individuals. We further explored developmental trajectories and the moderating roles of gender, measurement, geography and ancestry. We found all NDDs to be substantially heritable (family-based heritability, 0.66 (s.e. = 0.03); SNP heritability, 0.19 (s.e. = 0.03)). Meta-analytic genetic correlations between NDDs were moderate (grand family-based genetic correlation, 0.36 (s.e. = 0.12); grand SNP-based genetic correlation, 0.39 (s.e. = 0.19)) but differed substantially between pairs of disorders. The genetic overlap between NDDs and DICCs was strong (grand family-based genetic correlation, 0.62 (s.e. = 0.20)). While our work provides evidence to inform and potentially guide clinical and educational diagnostic procedures and practice, it also highlights the imbalance in the research effort that has characterized developmental genetics research.

Investigating Direct and Indirect Genetic Effects in Attention-Deficit/Hyperactivity Disorder Using Parent-Offspring Trios

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) is highly heritable, but little is known about the relative effects of transmitted (i.e., direct) and nontransmitted (i.e., indirect) common variant risks. Using parent-offspring trios, we tested whether polygenic liability for neurodevelopmental and psychiatric disorders and lower cognitive ability is overtransmitted to ADHD probands. We also tested for indirect or genetic nurture effects by examining whether nontransmitted ADHD polygenic liability is elevated. Finally, we examined whether complete trios are representative of the clinical ADHD population.

METHODS

Polygenic risk scores (PRSs) for ADHD, anxiety, autism, bipolar disorder, depression, obsessive-compulsive disorder, schizophrenia, Tourette syndrome, and cognitive ability were calculated in UK control subjects (n = 5081), UK probands with ADHD (n = 857), their biological parents (n = 328 trios), and also a replication sample of 844 ADHD trios.

RESULTS

ADHD PRSs were overtransmitted and cognitive ability and obsessive-compulsive disorder PRSs were undertransmitted. These results were independently replicated. Overtransmission of polygenic liability was not observed for other disorders. Nontransmitted alleles were not enriched for ADHD liability compared with control subjects. Probands from incomplete trios had more hyperactive-impulsive and conduct disorder symptoms, lower IQ, and lower socioeconomic status than complete trios. PRS did not vary by trio status.

CONCLUSIONS

The results support direct transmission of polygenic liability for ADHD and cognitive ability from parents to offspring, but not for other neurodevelopmental/psychiatric disorders. They also suggest that nontransmitted neurodevelopmental/psychiatric parental alleles do not contribute indirectly to ADHD via genetic nurture. Furthermore, ascertainment of complete ADHD trios may be nonrandom, in terms of demographic and clinical factors.

The role of self-compassion in the mental health of adults with ADHD

OBJECTIVE

Evidence suggests that the poorer mental health associated with attention deficit hyperactivity Disorder (ADHD) is partially explained by adverse psychosocial correlates of the condition. As recent studies show that self-compassion is negatively associated with ADHD, this study investigates if levels of self-compassion may explain the mental health outcomes in people with ADHD compared to people without ADHD.

METHOD

A total of 543 adults with ADHD (62.72% female, 18-67 years), and 313 adults without ADHD (66.45% female, 18-82 years) completed questionnaires online to measure levels of self-compassion and mental health. A Structural Equation Model assessed the mediating effect of self-compassion on the relationships between ADHD and well-being (psychological, emotional, and social), and ADHD and ill-being (depression, anxiety, and stress).

RESULTS

Findings suggest that low self-compassion contributes to poorer mental health in adults with ADHD compared to adults without ADHD.

CONCLUSIONS

Thus, self-compassion may be a potential target to improve mental health in this population.

PUBLIC HEALTH SIGNIFICANCE

This study shows that self-compassion is an important factor in the mental health of adults with ADHD and provides preliminary evidence for the use of self-compassion interventions to improve mental health outcomes in adults with ADHD.

ADHD in adults with major depressive or bipolar disorder: does it affect clinical features, comorbidity, quality of life, and global functioning?

BACKGROUND

This study compared clinical characteristics, concurrent disorders, level of function, and quality of life in adults with bipolar (BD) or major depressive disorder (MDD) in those with/without adult attention defici1t hyperactivity disorder (AADHD).

METHODS

The participants were recruited among adult inpatients and outpatients with MDD or BD in their current partial remission in a psychiatric hospital. They were evaluated using the interview for adults with ADHD (DIVA-5), Conners' Adult ADHD Rating Scales-Self-Report-Screening Version (CAARS-SR-SV), Structured Clinical Interview for DSM-V (SCID-5), Beck Depression Inventory-II and Young Mania Rating Scale, Global Assessment of Functioning (GAF) and World Health Organization Quality of Life Scale-Brief (WHOQoL-BREF).

RESULTS

In those with MDD (n = 105) and BD (n = 103), AADHD was detected as 13.3% and 16.5%, respectively. The inattentive presentation was the most prevalent type among patients with AADHD. Compared to the patients without AADHD, the results regarding the prevalence of comorbidities, suicidal attempts, severity of affective episodes, the early emergence of the affective disorders, and level of quality of life and global functioning were poorer in the group with AADHD (p < 0.05).

LIMITATIONS

The participants were individuals with major depressive or bipolar type I disorder with a mostly manic episode, chosen among the referrals to a tertiary psychiatric hospital with high comorbidity and more severe psychopathology. This may limit the generalizability of the findings.

CONCLUSION

ADHD was common in adults with MDD and BD, along with high psychiatric comorbidity and negative consequences. Clinicians are suggested to screen adults with mood disorders for the symptoms of ADHD for a more precise and comprehensive diagnosis and to provide a more appropriate therapeutic intervention.

Genetics of Attention-Deficit Hyperactivity Disorder

Attention-Deficit Hyperactivity Disorder (ADHD) has long been recognized as being a highly heritable condition and our understanding of the genetic contributions to ADHD has grown over the past few decades. This chapter will discuss the studies that have examined its heritability and the efforts to identify specific genetic risk-variants at the molecular genetic level. We outline the various techniques that have been used to characterize genetic contributions to ADHD, describing what we have learnt so far, what there is still to learn and the methodologies that can be used to further our knowledge. In doing so we will discuss research into rare and common genetic variants, polygenic risk scores, and gene-environment interplay, while also describing what genetic studies have revealed about the biological processes involved in ADHD and what they have taught us about the overlap between ADHD and other psychiatric and somatic disorders. Finally, we will discuss the strengths and limitations of the current methodologies and clinical implications of genetic research to date.

A scoping review and comparison of approaches for measuring genetic heterogeneity in psychiatric disorders

An improved understanding of genetic etiological heterogeneity in a psychiatric condition may help us (a) isolate a neurophysiological 'final common pathway' by identifying its upstream genetic origins and (b) facilitate characterization of the condition's phenotypic variation. This review aims to identify existing genetic heterogeneity measurements in the psychiatric literature and provides a conceptual review of their mechanisms, limitations, and assumptions. The Scopus database was searched for studies that quantified genetic heterogeneity or correlation of psychiatric phenotypes with human genetic data. Ninety studies were included. Eighty-seven reports quantified genetic correlation, five applied genomic structural equation modelling, three evaluated departure from the Hardy-Weinberg equilibrium at one or more loci, and two applied a novel approach known as MiXeR. We found no study that rigorously measured genetic etiological heterogeneity across a large number of markers. Developing such approaches may help better characterize the biological diversity of psychopathology.

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.

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.

Latrophilin-3 disruption: Effects on brain and behavior

Latrophilin-3 (LPHN3), a G-protein-coupled receptor belonging to the adhesion subfamily, is a regulator of synaptic function and maintenance in brain regions that mediate locomotor activity, attention, and memory for location and path. Variants of LPHN3 are associated with increased risk for attention deficit hyperactivity disorder (ADHD) in some patients. Here we review the role of LPHN3 in the central nervous system (CNS). We describe synaptic localization of LPHN3, its trans-synaptic binding partners, links to neurodevelopmental disorders, animal models of Lphn3 disruption in different species, and evidence that LPHN3 is involved in cognition as well as activity and attention. The evidence shows that LPHN3 plays a more significant role in neuroplasticity than previously appreciated.

Genetically Informed Regression Analysis: Application to Aggression Prediction by Inattention and Hyperactivity in Children and Adults

We present a procedure to simultaneously fit a genetic covariance structure model and a regression model to multivariate data from mono- and dizygotic twin pairs to test for the prediction of a dependent trait by multiple correlated predictors. We applied the model to aggressive behavior as an outcome trait and investigated the prediction of aggression from inattention (InA) and hyperactivity (HA) in two age groups. Predictions were examined in twins with an average age of 10 years (11,345 pairs), and in adult twins with an average age of 30 years (7433 pairs). All phenotypes were assessed by the same, but age-appropriate, instruments in children and adults. Because of the different genetic architecture of aggression, InA and HA, a model was fitted to these data that specified additive and non-additive genetic factors (A and D) plus common and unique environmental (C and E) influences. Given appropriate identifying constraints, this ADCE model is identified in trivariate data. We obtained different results for the prediction of aggression in children, where HA was the more important predictor, and in adults, where InA was the more important predictor. In children, about 36% of the total aggression variance was explained by the genetic and environmental components of HA and InA. Most of this was explained by the genetic components of HA and InA, i.e., 29.7%, with 22.6% due to the genetic component of HA. In adults, about 21% of the aggression variance was explained. Most was this was again explained by the genetic components of InA and HA (16.2%), with 8.6% due to the genetic component of InA.

Disruption of Pharmacotherapy During the Transition from Adolescence to Early Adulthood in Patients with Attention-Deficit/Hyperactivity Disorder: A Claims Database Analysis Across the USA

BACKGROUND AND OBJECTIVE

Attention-deficit/hyperactivity disorder (ADHD) treatment rates in adults are low, possibly owing to discontinuation of pediatric care due to various circumstances (including inadequate health insurance coverage, poor disease insight, and patient/family resistance, as well as those who manage their ADHD independent of pharmacologic intervention) during the transition from adolescence to adulthood. To improve the understanding of treatment patterns during this transition, this study characterized pharmacotherapy use in patients with ADHD aged 16-21 years.

METHODS

A retrospective claims analysis of the IBM^® MarketScan^® Commercial Databases, which represent all census regions of the USA, included patients aged 16-21 years with two or more ADHD diagnoses between 1/1/2008 and 12/31/2017 (one or more diagnoses during the year of age 17) who were continuously enrolled from ages 16-21 years and prescribed ADHD medication for ≥ 6 months at age 17 years. Pharmacotherapy use was assessed longitudinally. Comparisons between ages were conducted using Wilcoxon signed-rank tests and McNemar tests. Treatment discontinuation was estimated using Kaplan-Meier analyses.

RESULTS

The analysis included 10,292 patients. The overall percentage of patients receiving pharmacotherapy significantly decreased (p < 0.001, regardless of treatment type and presence of co-occurring psychiatric disorders) as patients aged, with a median time to treatment discontinuation of 2.94 years. Among patients using pharmacotherapy at the age of 17 years, more than 30% were no longer using pharmacotherapy at age 21 years. As patients aged, the percentage using long-acting amphetamines or methylphenidates decreased, and the percentage receiving no treatment increased. The percentage of patients with disrupted treatment from age 18 to 21 years ranged from 17.9 to 24.1%. After transitioning to disrupted treatment or no treatment, low percentages of patients returned to pharmacotherapy use (disrupted treatment: 15.7-21.5% per year; no treatment, 2.7-3.8% per year). Across all age groups, statistically significantly greater (p < 0.05) percentages of patients with co-occurring psychiatric disorders used lisdexamfetamine, dextroamphetamine-amphetamine mix short acting, and non-stimulants compared with patients without co-occurring psychiatric disorders. Patients with co-occurring psychiatric disorders remained on ADHD pharmacotherapy longer and switched or augmented their pharmacotherapy more frequently than patients without co-occurring psychiatric comorbidities.

CONCLUSIONS

Patients rarely reinitiated treatment after pharmacotherapy was disrupted or discontinued, emphasizing the need for increased focus on the management of ADHD as patients transition from adolescence to adulthood.

Overlap between attention-deficit hyperactivity disorder and neurodevelopmental, externalising and internalising disorders: separating unique from general psychopathology effects

BACKGROUND

Although attention-deficit hyperactivity disorder (ADHD) is classified as a neurodevelopmental disorder in the latest diagnostic manuals, it shows phenotypic and genetic associations of similar magnitudes across neurodevelopmental, externalising and internalising disorders.

AIMS

To investigate if ADHD is aetiologically more closely related to neurodevelopmental than externalising or internalising disorder clusters, after accounting for a general psychopathology factor.

METHOD

Full and maternal half-sibling pairs (N = 774 416), born between 1980 and 1995, were identified from the Swedish Medical Birth and Multi-Generation Registers, and ICD diagnoses were obtained from the Swedish National Patient Register. A higher-order confirmatory factor analytic model was fitted to examine associations between ADHD and a general psychopathology factor, as well as a neurodevelopmental, externalising and internalising subfactor. Quantitative genetic modelling was performed to estimate the extent to which genetic, shared and non-shared environmental effects influenced the associations with ADHD.

RESULTS

ADHD was significantly and strongly associated with all three factors (r = 0.67-0.75). However, after controlling for a general psychopathology factor, only the association between ADHD and the neurodevelopmental-specific factor remained moderately strong (r = 0.43, 95% CI = 0.42-0.45) and was almost entirely influenced by genetic effects. In contrast, the association between ADHD and the externalising-specific factor was smaller (r = 0.25, 95% CI = 0.24-0.27), and largely influenced by non-shared environmental effects. There remained no internalising-specific factor after accounting for a general factor.

CONCLUSIONS

Findings suggest that ADHD comorbidity is largely explained by genetically influenced general psychopathology, but the strong link between ADHD and other neurodevelopmental disorders is also substantially driven by unique genetic influences.

Advances in early identification of children and adolescents at risk for psychiatric illness

PURPOSE OF REVIEW

Childhood and adolescence are a crucial time window for the early identification of perspectival risk for adult psychopathology. This article reviews current advances in the field.

RECENT FINDINGS

Converging developmentally focused and predictive approaches are rapidly expanding in the field of early identification of children and adolescents at risk for psychiatric illness. Although the former emphasizes early phenotypic trajectories emerging in childhood and adolescence, the latter operate in terms of clinical risk staging. Decisive advances in the field include the metaanalytical evidence of the predictive value of clinical high-risk criteria in childhood-adolescence; the systematization of premorbid manifestations of psychotic vulnerability and bipolar prodromes; the corroboration of certain sets of anomalous subjective experiences as transdiagnostic index of familial genetic risk (i.e., basic symptoms) and early developmental expression of schizophrenia spectrum vulnerability (i.e., self-disorders).

SUMMARY

Childhood phenotypic manifestations of liability to mental disorders are often cooccurrent and undergo a plastic, heterotypic modification along the transition to adolescence. In general, they represent epiphenomenic flags of a broad vulnerability for the subsequent structuration of mental illness. This perspective coheres with the p-factor model of psychopathology and complements the clinical staging model which informs the early detection paradigm of severe mental disorders.