Impaired working memory in children with attention deficit hyperactivity disorder and their siblings

Introduction: Impairment of working memory in children with attention deficit hyperactivity disorder (ADHD) has been well described. If similar impairment in working memory can be demonstrated among their siblings, this could suggest impaired working memory is a genetic component of ADHD. Methods: Fifty-seven subjects were recruited: (1) ADHD group (n=21); (2) siblings of ADHD children group (n=15); and (3) non-ADHD children with chronic medical condition as the control group (n=21). All subjects were aged between 6 and 15 years, and ADHD was diagnosed according to DSM-IV-TR. Those with other comorbidity or IQ<70 were excluded. Digit Recall was used for assessment of the phonological loop component, Maze Memory test for the visuospatial sketch pad component and Backward Digit Recall for the central executive component of working memory. Results: ADHD children and their siblings showed similar impairment and both differed from the control group on the Maze Memory test. ADHD children also showed impairment in the Digit Recall test; however, the sibling group did not differ from the control group on this test. The Backward Digit Recall score did not show any significant difference between the three groups. Discussion: Impairment of the visuospatial sketch pad component of working memory seems to cluster in ADHD children and their siblings. Thus, impairment of the visuospatial sketch pad component of working memory may point towards a genetic predisposition of ADHD.