A Thapar1, R Harrington, K Ross, P McGuffin. 1. Department of Psychological Medicine, University of Wales College of Medicine, Cardiff, UK. Thapar@cardiff.ac.uk
Abstract
OBJECTIVE: A twin study design was used to examine the genetic validity of attention-deficit hyperactivity disorder (ADHD)-related phenotypes. METHOD: Questionnaires covering ADHD symptoms were sent to the families of 2,846 school-age twins. Parent-rated symptoms were obtained for 2,082 twin pairs and teacher-rated symptoms were available for 1,470 twin pairs. RESULTS: Broadly defined parent-rated, teacher-rated, and "pervasive" (both parent- and teacher-rated) ADHD categories were found to be highly heritable. Significant shared environmental effects were also detected for teacher-rated ADHD. A common genetic factor was found to have a modest influence on both parent- and teacher-rated symptom scores and categories, but additional genetic and environmental influences were also found forteacher-rated ADHD. Consistent with previous findings, ADHD symptom scores were again found to be highly heritable. Maternal contrast effects were found for the Rutter A scale items but could not be detected for the DuPaul ADHD rating scale. CONCLUSIONS: Broadly defined pervasive ADHD appears to be as heritable as ADHD behaviors defined by maternal reports alone. A common genetic factor influences maternally rated and teacher-rated ADHD but does not account for all of the genetic variance for teacher-rated ADHD. ADHD symptom scores are highly heritable, and maternal contrast effects appear to vary for different measures.
OBJECTIVE: A twin study design was used to examine the genetic validity of attention-deficit hyperactivity disorder (ADHD)-related phenotypes. METHOD: Questionnaires covering ADHD symptoms were sent to the families of 2,846 school-age twins. Parent-rated symptoms were obtained for 2,082 twin pairs and teacher-rated symptoms were available for 1,470 twin pairs. RESULTS: Broadly defined parent-rated, teacher-rated, and "pervasive" (both parent- and teacher-rated) ADHD categories were found to be highly heritable. Significant shared environmental effects were also detected for teacher-rated ADHD. A common genetic factor was found to have a modest influence on both parent- and teacher-rated symptom scores and categories, but additional genetic and environmental influences were also found forteacher-rated ADHD. Consistent with previous findings, ADHD symptom scores were again found to be highly heritable. Maternal contrast effects were found for the Rutter A scale items but could not be detected for the DuPaul ADHD rating scale. CONCLUSIONS: Broadly defined pervasive ADHD appears to be as heritable as ADHD behaviors defined by maternal reports alone. A common genetic factor influences maternally rated and teacher-rated ADHD but does not account for all of the genetic variance for teacher-rated ADHD. ADHD symptom scores are highly heritable, and maternal contrast effects appear to vary for different measures.
Authors: Esther A Croes; Rachid El Galta; Jeanine J Houwing-Duistermaat; Robert F Ferdinand; Sandra López León; Tessa A M Rademaker; Marieke C J Dekker; Ben A Oostra; Frank Verhulst; Cornelia M Van Duijn Journal: Eur J Epidemiol Date: 2005 Impact factor: 8.082
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