Genetic and environmental influences on attention-deficit/hyperactivity disorder symptoms in Chinese adolescents: a longitudinal twin study.

Attention-deficit/hyperactivity disorder (ADHD) is a highly heritable neurodevelopmental disorder. However, no study has examined genetic and environmental influences in the longitudinal developmental course of ADHD symptoms in a non-Western population. This study investigated changes of genetic and environmental influences and their contributions to the stability and change of ADHD symptoms of hyperactivity/impulsivity and inattention in Chinese adolescent twins. A prospective sample of 602 twin pairs (48% male) self-reported both DSM-IV ADHD symptom subscales three times at the approximate age of 12, 13, and 15 years. Longitudinal multivariate genetic analyses through structural equation modelling examined genetic and environmental contributions to the developmental course of ADHD symptoms. From early (time 1 and 2) to middle adolescence (time 3), both symptoms showed modest and non-significant genetic influences that became substantial and significant, whereas shared environmental influences were substantial and significant and became modest and non-significant. The same genetic factors influenced ADHD symptoms throughout adolescence, while shared and non-shared environmental influences largely came from new emerging factors. In early adolescence, genetic factor contributed to the stability of inattention, whereas shared environmental factor contributed to the stability of hyperactivity/impulsivity. Genetic influences of ADHD tended to be smaller, whereas shared environmental influences tended to be larger in Chinese than in Western populations. Genetic factors played a large role in the stability of ADHD throughout adolescence, while shared and non-shared environment primarily contributed to its change. Findings highlight the importance of shared family, neighbourhood, and community experiences on child psychopathology in a collectivistic culture such as the Chinese society.