Background: Despite the well-replicated relationship between the home literacy environment and expressive vocabulary, few studies have examined the extent to which the home literacy environment is associated with the development of early vocabulary ability in the context of genetic influences. This study examined the influence of the home literacy…

In old and even middle age, there are associations between physical health and both intelligence and education. This may occur because intelligence and/or education exert effects on lifestyle choices that, in turn, affect later health. Substance use is one aspect of lifestyle choice in young adulthood that could play such a role. The effects of…

Antisocial behavior increases in adolescence, particularly among those who perform poorly in school. As adolescents move into adulthood, both educational attainment and the extent to which antisocial behavior continues have implications for adolescents' abilities to take on constructive social roles. The authors used a population-representative…

The etiology of individual differences in general verbal ability, verbal learning and letter and category fluency were examined in two independent samples of 9- and 18-year-old twin pairs and their siblings. In both age groups, we observed strong familial resemblance for general verbal ability and moderate familial resemblance for verbal learning,…

This paper reports on the contribution of prenatal stress to the pathogenesis of autism as a neurobiological developmental disorder in a dizygotic study. The aim was to explore whether the neurobiological impact of stress prior to week 28 of gestation might be related to the pathogenesis of autism. The following data-generating strategies were…

Purpose: Language acquisition is predictive of successful reading development, but the nature of this link is poorly understood. Method: A sample of 7,179 twin pairs was assessed on parent-report measures of syntax and vocabulary at ages 2, 3, and 4 years and on teacher assessments of reading achievement (RA) at ages 7, 9, and 10 years. These…

Background: Three groups of children are involved in bullying: victims, bullies and bully-victims who are both bullies and victims of bullying. Understanding the origins of these groups is important since they have elevated emotional and behavioural problems, especially the bully-victims. No research has examined the genetic and environmental…

In this paper we assess the presence of assortative mating, gene-environment interaction and the heritability of intelligence in childhood using a twin family design with twins, their siblings and parents from 112 families. We evaluate two competing hypotheses about the cause of assortative mating in intelligence: social homogamy and phenotypic…

Background: DSM-IV specifies three ADHD subtypes; the combined, the hyperactive-impulsive and the inattentive. Little is known about the developmental relationships underlying these subtypes. The objective of this study was to describe the development of parent-reported hyperactivity-impulsivity and inattention symptoms from childhood to…

Experts have yet to reach consensus about what a learning disability is, how to determine if a child has one, and what to do about it. Leading researcher and clinician Deborah Waber offers an alternative to the prevailing view of learning disability as a problem contained within the child. Instead, she shows how learning difficulties are best…

Individuals with dyslexia are at an increased risk for anxiety disorders (e.g. generalized anxiety disorder, stress disorders, panic disorder). The extent to which this association is mediated by genetic and/or environmental influences is unclear. The current study explored the relationship between these two phenotypes using a large…

Objective: Evidence suggests that there is substantial comorbidity between attention-deficit/hyperactivity disorder (ADHD) and major depressive disorder in childhood and adolescence. This study aims to investigate the degree to which etiological factors are shared between the symptoms of these significantly heritable disorders. Method: A twin…

A previous finding from our group indicated that teacher-rated antisocial behaviour (AB) among 7-year-olds is particularly heritable in the presence of callous-unemotional (CU) traits. Using a sample of 1865 same-sex twin pairs, we employed DeFries-Fulker extremes analysis to investigate whether teacher-rated AB with/without CU traits also shows…

Background: Comorbidity amongst anxiety disorders is very common in children as in adults and leads to considerable distress and impairment, yet is poorly understood. Multivariate genetic analyses can shed light on the origins of this comorbidity by revealing whether genetic or environmental risks for one disorder also influence another. We…

Understanding the development of religiousness is an important endeavor because religiousness has been shown to be related to positive outcomes. The current study examined mean-level, rank-order, and individual-level change in females' religiousness during emerging adulthood. Genetic and environmental influences on religiousness and its change and…