ABSTRACT
Attention Deficit Hyperactivity Disorder (ADHD) is a developmental disorder. In the Diagnostic and Statistical Manual of Mental Disorders, fourth edition by definition symptoms must appear before the age of 7 years. During the past 20 years there have been massive longitudinal genetic studies of the development of cognition, both in twins and in adopted children. A very different study design was used in the Virginia Twin Study of Adolescent Behavioral Development, to examine age changes from age 8 to age 16 years in the genetics of hyperactivity, conduct disturbance, and their covariance. The univariate results were complex, varying between behaviour, ages, and genders. However, the bivariate models for the relationship between the Hyperactivity and Conduct Disturbance traits showed that essentially all of the relationship between the two behaviours was genetic in the younger group. Many families do not seek help for young people with Inattentive symptoms.
