Recent developments in the genetics of attention-deficit hyperactivity disorder

Genetic Relationships between Attention-Deficit/Hyperactivity Disorder, Autism Spectrum Disorder, and Intelligence

INTRODUCTION

Attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) commonly co-occur; both traits exert an influence on intelligence scores. Genetic relationships between these three traits are far from being clear.

METHODS

The summary results of genome-wide association studies of ADHD (20,183 cases and 35,191 controls), ASD (18,381 cases and 27,969 controls), and intelligence (269,867 participants) were used for the analyses. Local genetic correlation analysis and polygenic overlap analysis were used to explore the shared genetic components between ADHD, ASD, and intelligence. Mendelian randomization (MR) analysis was used to examine the causal associations between ADHD, ASD, and intelligence. A cross-trait meta-analysis was performed to identify pleiotropic genetic variants across the three traits.

RESULTS

Our results showed that intelligence has a positive and negative genetic correlation with ASD and ADHD, respectively, including three hub genomic regions showing correlated genetic effects across the three traits. Polygenic overlap analysis indicated that all the risk variants contributing to ADHD are overlapped with half of those for intelligence, and the majority of the shared variants have opposite effect directions between them. The majority of risk variants (80%) of ASD are overlapped with almost all the risk variants of intelligence (97%). Notably, some ASD/intelligence overlapping variants displayed opposing effects on these two conditions. MR analysis showed that the genetic liability to higher intelligence was associated with an increased risk for ASD (OR = 1.12) and a decreased risk for ADHD (OR = 0.78). Cross-trait meta-analyses identified 170 pleiotropic genomic loci across the three traits, including 12 novel loci. Functional analyses of the novel genes support their potential involvement in neurodevelopment.

CONCLUSION

Our results suggest that ADHD is associated with inheriting a reduced set of low-intelligence alleles, whereas ASD results from incongruous effects from a mixture of high-intelligence and low-intelligence contributing alleles summed up with additional, ASD-specific risk variants not associated with intelligence.

Shared genetics between autism spectrum disorder and attention-deficit/hyperactivity disorder and their association with extraversion

BACKGROUND

Deciphering the genetic relationships between autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) may uncover underlining shared pathophysiology as well as inform treatment.

METHODS

The summary results of genome-wide association studies on ADHD, ASD, and extraversion were utilized for the analyzes. Genetic correlations between ADHD, ASD, and extraversion were tested using linkage disequilibrium score regression. Causal relationships between ADHD, ASD, and extraversion were investigated using Mendelian randomization (MR) analysis. Novel pleiotropic genomic loci shared by ADHD and ASD were identified using a cross-trait meta-analysis.

RESULTS

Extraversion was positively correlated with ADHD (r_g = 0.205) and negatively correlated with ASD (r_g = -0.193). The MR analysis showed that ADHD confers a causal effect on ASD (OR: 1.35, 95% confidence interval (CI):1.20-1.52) and vice versa (1.46, 1.38-1.55). Extraversion exerts a causal effect on ADHD only (1.19, 1.05-1.33). The cross-trait meta-analysis identified three novel pleiotropic genomic loci for ADHD and ASD, involving two pleiotropic genes, LINC00461 and KIZ.

CONCLUSIONS

Our study provides new insights into the shared genetics of ADHD and ASD and their connections with extraversion.

Gut microbiota and probiotic therapy in ADHD: A review of current knowledge

Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder characterized by inattention, impulsivity and hyperactivity. The etiology of the disorder is multi-factorial, with a main focus on genetic factors. However, emerging research shows the involvement of changes and imbalances in the intestinal microbiota. Evidence for the influence of gut microbiota on brain development and neurogenesis is clear. We present a review of emerging research on the microbiota in the ADHD population. The aim of this study was to summarize the current state of knowledge on ADHD, to identify gaps in knowledge, as well as to indicate the directions of new research. Thanks to the researchers that would be possible to better understand the complexity of ADHD etiology, especially the role of the intestinal microbiota in the pathogenesis of the disorder. Pubmed, Scopus and Google Scholar databases were used while writing the review. Numerous studies show that probiotic supplementation can have a positive effect on the course of neurodevelopmental disorders, including ADHD. Unfortunately, clinical studies that were identified are mostly inconclusive, and more high-quality research is needed to produce robust evidence for therapy based on interventions targeting microbiota.

Understanding ADHD: Toward an Innovative Therapeutic Intervention

Attention deficit hyperactivity disorder (ADHD) is a pervasive condition affecting persons across all age groups, although it is primarily diagnosed in children. This neurological condition affects behavior, learning, and social adjustment and requires specific symptomatic criteria to be fulfilled for diagnosis. ADHD may be treated with a combination of psychological or psychiatric therapeutic interventions, but it often goes unattended. People with ADHD face societal bias challenges that impact how they manage the disorder and how they view themselves. This paper summarizes the present state of understanding of this disorder, with particular attention to early diagnosis and innovative therapeutic intervention. Contemporary understanding of the mind-brain duality allows for innovative therapeutic interventions based on neurological stimulation. This paper introduces the concept of neurostimulation as a therapeutic intervention for ADHD and poses the question of the relationship between patient adherence to self-administered therapy and the aesthetic design features of the neurostimulation device. By fabricating devices that go beyond safety and efficacy to embrace the aesthetic preferences of the patient, it is proposed that there will be improvements in patient adherence to a device intended to address ADHD.

Appropriateness of array-CGH in the ADHD clinics: A comparative study

Attention deficit hyperactivity disorder (ADHD) is one of the most common neurodevelopmental disorder with a worldwide prevalence of about 5%. The disorder is characterized by inattentive, hyperactive and impulsive behavior and is often comorbid with other neuropsychiatric conditions. Array comparative genomic hybridization (array-CGH) testing has been proved to be useful to detect chromosomal aberrations in several neuropsychiatric conditions including autism spectrum disorders (ASD) and intellectual disability (ID). The usefulness of array-CGH in the ADHD clinics is still debated and no conclusive evidence has been reached to date. We performed array-CGH in 98 children and adolescents divided in two similarly sized groups according to the clinical diagnosis: (a) one group diagnosed with ADHD as primary diagnosis; (b) the other group in which ADHD was co-morbid with ASD and/or ID. We detected pathogenetic and likely pathogenetic copy number variants (CNVs) in 12% subjects in which ADHD was co-morbid with autism and/or intellectual disability and in 8.5% subjects diagnosed with ADHD as primary diagnosis. Detection of CNVs of unknown clinical significance was similar in the two groups being 27% and 32%, respectively. Benign and likely benign CNVs accounted for 61% and 59.5% in the first and second group, respectively. Differences in the diagnostic yield were not statistically significant between the two groups (P > .05). Our data strongly suggest that array-CGH (a) is a valuable diagnostic tool to detect clinically significant CNVs in individuals with ADHD even in the absence of comorbidity with ASD and/or ID and (b) should be implemented routinely in the ADHD clinics.

Impulsivity and Venturesomeness in an Adult ADHD Sample: Relation to Personality, Comorbidity, and Polygenic Risk

While impulsivity is a basic feature of attention-deficit/hyperactivity disorder (ADHD), no study explored the effect of different components of the Impulsiveness (Imp) and Venturesomeness (Vent) scale (IV7) on psychiatric comorbidities and an ADHD polygenic risk score (PRS). We used the IV7 self-report scale in an adult ADHD sample of 903 patients, 70% suffering from additional comorbid disorders, and in a subsample of 435 genotyped patients. Venturesomeness, unlike immediate Impulsivity, is not specific to ADHD. We consequently analyzed the influence of Imp and Vent also in the context of a PRS on psychiatric comorbidities of ADHD. Vent shows a distinctly different distribution of comorbidities, e.g., less anxiety and depression. PRS showed no effect on different ADHD comorbidities, but correlated with childhood hyperactivity. In a complementary analysis using principal component analysis with Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition ADHD criteria, revised NEO Personality Inventory, Imp, Vent, and PRS, we identified three ADHD subtypes. These are an impulsive-neurotic type, an adventurous-hyperactive type with a stronger genetic component, and an anxious-inattentive type. Our study thus suggests the importance of adventurousness and the differential consideration of impulsivity in ADHD. The genetic risk is distributed differently between these subtypes, which underlines the importance of clinically motivated subtyping. Impulsivity subtyping might give insights into the organization of comorbid disorders in ADHD and different genetic background.

Increased prevalence of parent ratings of ADHD symptoms among children with bilateral congenital cataracts

AIM

To investigate the behavioral and psychological disorders and the prevalence of parent ratings of attention deficit hyperactivity disorder (ADHD) symptoms among children with bilateral congenital cataracts (CCs).

METHODS

This cross-sectional study investigated children with bilateral CC aged 3-8y (CC group) using Conners' Parent Rating Scale-48 (CPRS-48) from July to December 2016. The abnormal rates of psychological symptoms in CC children and normal vision (NV) children were compared using the Chi-square test. The scores of CC children were compared with those of NV children and the Chinese urban norm using the independent samples t-test and one-sample t-test, respectively.

RESULTS

A total of 262 valid questionnaires were collected. The ratio of CC children to NV children was 119:143. The overall rate of psychological symptoms in CC children was 2.28 times higher than that in NV children (46.22% vs 20.28%, Pearson's χ ²=20.062; P<0.001). CC children showed higher scores for conduct problems, learning problems, impulsiveness/hyperactivity, anxiety, and hyperactivity index than NV children and the Chinese urban norm, particularly between the ages of 3 and 5y. Furthermore, male children aged between 6 and 8y showed a higher impulsive/hyperactive score than females of the same age (t=6.083, P<0.001).

CONCLUSION

Children with bilateral CCs have a higher rate of ADHD symptoms than children with NV. This study provides clinical evidence that screening for psychological symptoms and particularly for ADHD symptoms in children with bilateral CC are recommended for an early diagnosis and timely treatment.

Impaired Interparental Relationships in Families of Children With Attention-Deficit/Hyperactivity Disorder (ADHD)

Abstract. Research on attention-deficit/hyperactivity disorder (ADHD) in children and adolescents has traditionally focused on the genetic and neurobiological aspects of the disorder, but the role of family relationships has been much less systematically examined. There is growing evidence that the quality of interparental relationships and a child’s ADHD symptoms are reciprocally related. Because the literature appears to be inconsistent, this meta-analysis aims to summarize previous research and assess whether there are robust differences in the quality of interparental relationships between parents of children with ADHD and parents of healthy children. This meta-analysis of 15 studies with 43 effect sizes revealed a small but significant difference ( d = .24), which indicates that parents of a child with ADHD report poorer relationship quality than parents of healthy children. This effect was moderated by the child’s age and did not depend on whether the child had a comorbid oppositional defiant disorder (ODD) or conduct disorder (CD). The causality of this relationship has yet to be determined.

The association of maternal diabetes with attention deficit and hyperactivity disorder in offspring: a meta-analysis

OBJECTIVE

Recent controversial evidence suggests that maternal diabetes may increase the risk of attention deficit and hyperactivity disorder (ADHD) in offspring. To examine this potential association, a systematic literature search and meta-analysis was performed.

METHODS

OR or risk ratio (RR) from each study was obtained and combined for evaluating the risk. Six cohort studies and three case-control studies were included in the present study.

RESULTS

The meta-analysis of the highly heterogeneous case-control studies did not find significant association between maternal diabetes and ADHD risk (OR: 1.20, 95% CI: 0.96-1.49). The combining of the cohort studies demonstrated that offspring of diabetic mothers were at higher risk of ADHD (RR: 1.40, 95% CI: 1.27-1.54); however, publication bias was identified. When exposure was specified as gestational diabetes mellitus (GDM), GDM exposure increased the risk of ADHD for children by 164% (95% CI: 1.25-5.56) in a Caucasian population. Neither heterogeneity nor publication bias was detected.

CONCLUSION

Maternal diabetes, especially GDM, is probably a risk factor for ADHD in the Caucasian population. More studies based on large sample size and different ethnicities are needed to confirm this association.

Association of Affected Neurocircuitry With Deficit of Response Inhibition and Delayed Gratification in Attention Deficit Hyperactivity Disorder: A Narrative Review

The neural networks that constitute corticostriatothalamocortical circuits between prefrontal cortex and subcortical structure provide a heuristic framework for bridging gaps between neurocircuitry and executive dysfunction in attention deficit hyperactivity disorder (ADHD). “Cool” and “Hot” executive functional theory and the models of dual pathway are supposed to be applied within the neuropsychology of ADHD. The theoretical model elaborated response inhibition and delayed gratification in ADHD. We aimed to review and summarize the literature about the circuits on ADHD and ADHD-related comorbidities, as well as the effects of neurocircuitry on the executive dysfunction in ADHD.