Background: The seven papers in this special section chart where we are in the quest for quantitative trait loci (QTLs) in key areas of child psychology and psychiatry such as reading and hyperactivity. But we are not there yet. Methods: This commentary considers some new developments that are likely to accelerate the journey towards the…

Objective: To examine the etiologies of covariation of childhood sleep problems and other behavioral/emotional problems in young children. Method: The parents of more than 6,000 twin pairs provided information on their twins' anxiety, conduct, and hyperactivity at ages 3, 4, and 7 by completing the Strengths and Difficulties Questionnaire.…

Background: Childhood behavior problems predict subsequent educational achievement; however, little research has examined the etiology of these links using a longitudinal twin design. Moreover, it is unknown whether genetic and environmental innovations provide incremental prediction for educational achievement from childhood to adolescence.…

Background: Attention-deficit/hyperactivity disorder (ADHD) symptoms and mathematics ability are associated, but little is known about the genetic and environmental influences underlying this association. Methods: Data came from more than 6,000 twelve-year-old twin pairs from the UK population-representative Twins Early Development Study. Parents…

Background: The identification of specific nonshared environments responsible for the variance in behaviour problems is a key challenge. Methods: Nonshared environmental influences on teacher-reported behaviour problems were explored independently of genetics using the monozygotic (MZ) twin differences design. Six aspects of classroom environment…