Abstract

Background and objectives Behavior-genetic analyses have shown that measurements of inattention and hyperactivity–impulsivity are genetically-influenced. In view of limited studies on ADHD (Attention deficit hyperactivity disorder) in Spanish samples, this study aims to explore the genetic architecture of ADHD symptoms; inattention and hyperactivity–impulsivity in a Spanish twin schoolchildren sample.

Methods Participants were 258 pairs of adolescent Spanish twins. Symptoms of ADHD, inattention and hyperactivity–impulsivity were assessed by means of a sub-scale of the Strengths and Difficulties Questionnaire. Univariate twin models, according to sex, were run to assess the heritability of ADHD symptoms.

Results Heritability of hyperactivity was 55% in girls, 57% in boys. Inattention showed a heritability of 26% in girls, and no genetic factors influence was found in boys. Environmental factors are prominent influences among these traits.