Genetic mechanisms in childhood psychiatric disorders

Prenatal Exposure to Organophosphorus Pesticides and Preschool ADHD in the Norwegian Mother, Father and Child Cohort Study

Prenatal organophosphorus pesticide (OPP) exposure has been associated with child attention-deficit/hyperactivity disorder (ADHD) in agricultural communities and those that are exposed to residentially applied insecticides. To examine this association in populations that are exposed primarily through diet, we estimate the associations between prenatal OPP exposure and preschool ADHD in the Norwegian Mother, Father and Child Cohort Study (MoBa), and describe modification by paraoxonase 1 (PON1) gene variants. We used participants from the MoBa Preschool ADHD Sub-study (n = 259 cases) and a random sample of MoBa sub-cohort participants (n = 547) with birth years from 2004 to 2008. Prenatal urinary dialkylphosphate (DAP) metabolites (total diethylphosphate [∑DEP] and total dimethylphosphate [∑DMP]) were measured by an ultra-performance liquid chromatography-time-of-flight system and summed by molar concentration. Maternal DNA was genotyped for coding variants of PON1 (Q192R and L55M). We used a multivariable logistic regression to calculate the odds ratios (OR) and 95% confidence intervals, adjusted for maternal education, parity, income dependency, age, marital status, ADHD-like symptoms, pesticide use, produce consumption, and season. We found no associations between DAP metabolite concentrations and preschool ADHD. The adjusted ORs for exposure quartiles 2-4 relative to 1 were slightly inverse. No monotonic trends were observed, and the estimates lacked precision, likely due to the small sample size and variation in the population. We found no evidence of modification by PON1 SNP variation or child sex. Maternal urinary DAP concentrations were not associated with preschool ADHD.

The prevalence of psychopathology in siblings of children with mental health problems: a 20-year systematic review

While the importance of looking at the entire family system in the context of child and adolescent mental health is well recognised, siblings of children with mental health problems (MHPs) are often overlooked. The existing literature on the mental health of these siblings needs to be reviewed. A systematic search located publications from 1990 to 2011 in four electronic databases. Thirty-nine relevant studies reported data on the prevalence of psychopathology in siblings of target children with MHPs. Siblings of target children had higher rates of at least one type of psychopathology than comparison children. Risk of psychopathology varied across the type of MHP in the target child. Other covariates included sibling age and gender and parental psychopathology. Significant variations and limitations in methodology were found in the existing literature. Methodological guidelines for future studies are outlined. Implications for clinicians, parents, and for future research are discussed.

Attention-deficit/hyperactivity disorder genomics: update for clinicians

Attention deficit, hyperactivity disorder (ADHD) is familial and highly heritable. Several candidate genes involved in neurotransmission have been identified, however these confer minimal risk, suggesting that for the most part, ADHD is not caused by single common genetic variants. Advances in genotyping enabling investigation at the level of the genome have led to the discovery of rare structural variants suggesting that ADHD is a genomic disorder, with potentially thousands of variants, and common neuronal pathways disrupted by numerous rare variants resulting in similar ADHD phenotypes. Heritability studies in humans also indicate the importance of epigenetic factors, and animal studies are deciphering some of the processes that confer risk during gestation and throughout the post-natal period. These and future discoveries will lead to improved diagnosis, individualized treatment, cures, and prevention. These advances also highlight ethical and legal issues requiring management and interpretation of genetic data and ensuring privacy and protection from misuse.

Annual research review: impact of advances in genetics in understanding developmental psychopathology

It was hoped that diagnostic guidelines for, and treatment of, child psychiatric disorders in DSM-5 would be informed by the wealth of clinical genetic research related to neurodevelopmental disorders. In spite of remarkable advances in genetic technology, this has not been the case. Candidate gene, genome-wide association, and rare copy number variant (CNV) studies have been carried out for attention-deficit/hyperactivity disorder (ADHD), Autism, Tourette's Syndrome, and schizophrenia, with intriguing results, but environmental factors, incomplete penetrance, pleiotropy, and genetic heterogeneity, underlying any given phenotype have limited clinical translation. One promising approach may be the use of developmental brain imaging measures as more relevant phenotypes. This is particularly important, as subtle abnormalities in timing and expression of gene pathways underlying brain development may well link these disorders and be the ultimate target of treatments.

Parental ADHD status and its association with proband ADHD subtype and severity

OBJECTIVE

To better understand the familial transmission of attention deficit hyperactivity disorder (ADHD), a highly heritable disorder, the effects of paternal and maternal ADHD status on probands' ADHD symptoms and subtypes were investigated.

STUDY DESIGN

In 323 trios with ADHD, data from a structured interview and a self-report scale (score of >21) were used to determine ADHD probands' diagnostic status and parental ADHD status, respectively. Parental ADHD status on proband ADHD severity and subtypes was investigated.

RESULTS

ADHD criteria were endorsed by 23% of fathers and 27% of mothers, and by at least one parent in 41% of the cases. ADHD severity was higher for children whose parents had ADHD versus those whose parents were without it. Paternal ADHD was associated with an increased likelihood of ADHD combined subtype (odds ratio = 3.56) and a decreased likelihood of the inattentive subtype (odds ratio = 0.34) in male children.

CONCLUSIONS

Parental ADHD status appears to confer different risks for the severity of hyperactive-impulsive and inattentive symptoms depending on parental sex; however, parental ADHD self-report scale score has low to negligible correlation with proband's ADHD severity. Biparental ADHD does not appear to have an additive or synergistic effect on the proband's ADHD severity.

Parenting of 7-month-old infants at familial risk for attention deficit/hyperactivity disorder

Patterns of interaction between parents and 7-month-old boys at familial risk for attention deficit/hyperactivity disorder (ADHD) and a comparison group were studied during a warm-up and two play episodes. The sample included 78 (47 at-risk, 31 comparison) mother-child and 45 (27 at-risk, 18 comparison) father-child dyads. A coding system developed by G. Kochanska (1997, 1998) was used. Infants in the risk group did not differ from the comparison group in the rate of emission of infant-related events. However, they received less adequate responsivity from both their fathers and their mothers to these events, and specifically to negative emotions or distress, than did the comparison group. Maternal psychopathology did not account for these findings. Mothers were more adequately responsive than were fathers, especially for physiological needs. The association between nonoptimal interaction in infancy and the development of ADHD is discussed.

Autism and the development of face processing

Autism is a pervasive developmental condition, characterized by impairments in non-verbal communication, social relationships and stereotypical patterns of behavior. A large body of evidence suggests that several aspects of face processing are impaired in autism, including anomalies in gaze processing, memory for facial identity and recognition of facial expressions of emotion. In search of neural markers of anomalous face processing in autism, much interest has focused on a network of brain regions that are implicated in social cognition and face processing. In this review, we will focus on three such regions, namely the STS for its role in processing gaze and facial movements, the FFA in face detection and identification and the amygdala in processing facial expressions of emotion. Much evidence suggests that a better understanding of the normal development of these specialized regions is essential for discovering the neural bases of face processing anomalies in autism. Thus, we will also examine the available literature on the normal development of face processing. Key unknowns in this research area are the neuro-developmental processes, the role of experience and the interactions among components of the face processing system in shaping each of the specialized regions for processing faces during normal development and in autism.

Social interest and the development of cortical face specialization: what autism teaches us about face processing

Investigations of face processing in persons with an autism spectrum disorder (ASD) inform upon theories of the development of "normal" face processing, and the story that emerges challenges some models of the nature and origin of cortical face specialization. Individuals with an ASD possess deficits in face processing and a lack of a fusiform face area (FFA). Evidence from studies of ASD can be conceptualized best using an expertise framework of face processing rather than models that postulate a face module in the fusiform gyrus. Because persons with an ASD have reduced social interest, they may fail to develop cortical face specialization. Face specialization may develop in normal individuals because they are socially motivated to regard the face, and such motivation promotes expertise for faces. The amygdala is likely the key node in the system that marks objects as emotionally salient and could be crucial to the development of cortical face specialization.

Molecular and cytogenetic analyses on Brazilian youths with pervasive developmental disorders

The Pervasive Developmental Disorders (PDDs) constitute a group of behavioral and neurobiological impairment conditions whose main features are delayed communicative and cognitive development. Genetic factors are reportedly associated with PDDs and particular genetic abnormalities are frequently found in specific diagnostic subgroups such as the autism spectrum disorders. This study evaluated cytogenetic and molecular parameters in 30 youths with autism or other PDDs. The fragile X syndrome was the most common genetic abnormality detected, presented by 1 patient with autism and 1 patient with PPD not-otherwise specified (PPD-NOS). One girl with PDD-NOS was found to have tetrasomy for the 15q11-q13 region, and one patient with autism exhibited in 2/100 metaphases an inv(7)(p35q36), thus suggesting a mosaicism 46,XX/46,XX,inv(7)(p15q36) or representing a coincidental finding. The high frequency of chromosomopathies support the hypothesis that PDDs may develop as a consequence to chromosomal abnormalities and justify the cytogenetic and molecular assessment in all patients with PDDs for establishment of diagnosis.

The genetics of childhood psychiatric disorders: a decade of progress

OBJECTIVE

To review the literature over the past decade on the genetics of childhood neuropsychiatric disorders.

METHOD

A computerized search was performed for articles published in the past decade, and selected papers were highlighted.

RESULTS

The past decade of research has illuminated the complex genetics of early-onset mental disorders. Advances in statistical methodologies and laboratory-based gene-hunting techniques are laying the foundation for a deeper understanding of both the biological and environmental factors that contribute to mental illness. Researchers are on the verge of identifying and characterizing genetic vulnerabilities involved in common childhood psychiatric syndromes.

CONCLUSIONS

Although the study of the genetics of childhood psychiatric disorders has advanced significantly over the past decade, considerable work remains. The identification of genes conferring vulnerability to psychiatric illnesses will have the potential to transform the field by providing insight into both biological and environmental determinants that contribute to serious developmental and psychiatric disorders in children and adolescents. These advances promise new understanding and new avenues for prevention and treatment. They will also present physicians and families with significant clinical and ethical challenges.

Epidemiology of neurodevelopmental disorders in children

The epidemiology of mental and behavioural disorders is considered in comparison with spina bifida, chromosomal anomalies and brain tumours. Descriptive epidemiology is important not only in assessing the frequency of neurodevelopmental disorders, thereby aiding planning of service provision, but also because variations by geographical area, over time, and by personal characteristics provide clues regarding etiology. The value of the latter application is exemplified by research on spina bifida and other neural tube defects (NTDs). The descriptive epidemiology of mental and behavioural disorders has been less investigated. The descriptive epidemiology of NTDs suggested that diet might be of etiological importance. Analytical epidemiologic investigation proceeded by testing dietary hypotheses in case-control and cohort studies. Subsequently, folate supplementation was shown to reduce recurrence risk in a randomized controlled trial. The analytical epidemiology of other neurodevelopmental disorders is less well understood. Study design issues are discussed in relation to mental and behavioural disorders.

Hormonal and behavioral homeostasis in boys at risk for substance abuse

This study modeled the influences of cortisol reactivity, androgens, age-corrected pubertal status, parental personality, family and peer dysfunction on behavioral self-regulation (BSR), in boys at high (HAR) and low average risk (LAR) for substance abuse. Differences between risk groups in cortisol and androgen concentrations, and cortisol reactivity were also examined. Subjects were 10- through 12-year-old sons of substance abusing fathers (HAR; n = 150) and normal controls (LAR; n = 147). A multidimensional construct of BSR was developed which utilized multiple measures and multiple informants. Boys reported on family dysfunction and deviant behavior among their peers. Parents reported on their propensity to physically abuse their sons, and their own number of DSM-III-R Antisocial Personality Disorder symptoms. Endocrine measures included plasma testosterone, dihydrotestosterone, and salivary cortisol. HAR boys, compared to LAR boys, had lower mean concentrations for testosterone, dihydrotestosterone, salivary cortisol prior to evoked related potential testing, and lower cortisol reactivity. The number of maternal Antisocial Personality Disorder symptoms, parental potential for physical abuse, degree of family dysfunction, and peer delinquency were significantly associated with BSR. Parental aggression antisocial personality symptoms and parental physical abuse potential are likely to influence sons' behavioral dysregulation and homeostatic stress reactivity. These key components of liability are posited to increase the likelihood of developing suprathreshold Psychoactive Substance Use Disorder (PSUD).

Family and peer correlates of behavioral self-regulation in boys at risk for substance abuse

Behavioral self-regulation (BSR), defined herein as the degree to which one can control one's own activity and reactivity to environmental stimuli, has been posited to be salient to the onset of adolescent substance abuse. The goal of this study was to clarify particular family and peer correlates of BSR in at-risk sons. Subjects were 10-through 12-year-old sons of substance-abusing fathers (high-average risk [HAR]; n = 176) and normal controls (low-average risk [LAR]; n = 199). A BSR latent trait was developed using multiple measures and multiple informants. Analyses included separate hierarchical linear regressions for HAR and LAR groups. In the hierarchical linear model for HAR sons, family dysfunction and deviant peer affiliation were significantly associated with BSR, whereas for LAR sons, only peer affiliation was significantly associated with BSR. The above family and peer correlates differed in proportions of variance explained for BSR in HAR and LAR sons. These findings extend previous studies by showing that, in a hierarchical linear model, BSR in HAR sons is associated with specific interpersonal, family, and peer factors. These findings suggest that empirical, theory-guided interventions to prevent worsening of BSR in HAR boys should address specific interpersonal, family, and peer factors.

Brief report: a case of chromosome 22 alteration associated with autistic syndrome

The author described a male patient, age 13 years and 5 months, with behavioral profile meeting the criteria of the autistic syndrome by the DSM-III-R (APA, 1989) and DSM-IV (APA, 1995). After clinical and laboratory examinations, it was found that he had an abnormal karyotype, 46 XY, R(22). The need for clinical and laboratory case studies of autism is of great importance to develop data for defining an etiological basis for diagnosis.

Attention-deficit hyperactivity disorder dimensions: a twin study of inattention and impulsivity-hyperactivity

OBJECTIVE

This study used a model-fitting strategy to estimate genetic and environmental contributions to the core behavioral dimensions associated with attention-deficit hyperactivity disorder (ADHD) in 576 twin boys, aged 11 and 12 years.

METHOD

Teacher ratings and maternal structured interview reports composed of behavioral items including DSM-III and DSM-III-R criteria for ADHD were obtained for 194 pairs of monozygotic and 94 pairs of dizygotic twins. Factor analysis of these measures yielded two ADHD-related dimensions, inattention and impulsivity-hyperactivity. Scales representing these dimensions were used in the genetic analyses.

RESULTS

Univariate analyses supported a substantial contribution of genetic factors in the expression of inattention and impulsivity-hyperactivity and smaller contributions of shared and nonshared environmental factors. Results varied according to informant source, with mothers' reports suggestive of rater bias effects. Bivariate analyses indicated that the correlation between these two ADHD dimensions was also genetically mediated.

CONCLUSIONS

Genetic factors are etiologically important in the expression of the separate dimensions of ADHD and in the covariation between them. However, it is important to obtain reports from more than one informant because rater bias effects may be operative, particularly in maternal reports.

Attention deficit hyperactivity disorder in the presence of Tourette syndrome

Increasing attention to comorbidity in Tourette syndrome has led to a search for factors that would help in the development of treatment strategies for attention deficit hyperactivity disorder. Despite arguments and some research supporting various viewpoints, it is still unclear to what extent the frequency of co-occurrence is high in Tourette syndrome. It also is unclear whether attention deficit hyperactivity disorder and obsessive-compulsive disorder are part of a spectrum with related genetic or environmental factors. One of the main difficulties is obtaining a truly representative community sample and agreeing upon the categorical boundaries. The consequences of this argument are discussed. Effective treatment of attention deficit hyperactivity disorder in the presence of tics and Tourette syndrome has undergone considerable change from an absolute contraindication of stimulants to cautious use. For those whom stimulants fail or produce unacceptable side effects, nonstimulant medications are available in increasing variety. Much more methodologically adequate research needs to be undertaken with them.

Familial aggregation of psychiatric disorders in a community sample of adolescents

OBJECTIVE

To determine whether specific psychiatric disorders and suicide attempts ascertained in a community sample of adolescents show evidence of familial aggregation.

METHOD

Fifty-eight adolescent probands recruited from the community and their relatives were assessed as to the presence of specific DSM-III Axis I disorders and suicide attempt, using a combination of family study and family history methodology.

RESULTS

In first-degree relatives, there was evidence for specific familial aggregation of suicide attempt (odds ratio [OR] = 12.1 95% confidence interval [CI] = 1.3 to 111.0), substance abuse (OR = 2.7, 95% CI = 1.1 to 6.7), and any Axis I disorder (OR = 2.5, 95% CI = 1.3 to 4.6), even after demographic confounders and familial comorbidity were controlled. Similarly, among second-degree relatives, in analyses controlling for potentials confounders, the disorders-specific aggregation of suicide attempt (OR = 12.3, 95% CI = 1.2 to 130.0), substance abuse (OR = 2.8, 95% CI = 1.6 to 4.8), and any Axis I disorder (OR = 1.5, 95% CI = 1.0 to 2.2) persisted.

CONCLUSIONS

The familial aggregation of suicide attempts and psychiatric disorders, particularly of substance abuse and any Axis I disorder, occurs in community samples and is not primarily attributable to referral status.