| Objective. The purpose of the present study was to analyze the cognitive deficits, and their potential genetic underpinnings, in attention deficit hyperactivity disorder (ADHD) and childhood onset schizophrenia (COS), in an effort to explicate potential etiological commonalities between these two disorders. Methods. This study compared children with ADHD, children with COS, and control participants, aged 6-15, on measures of inhibition, working memory, and selective attention. It also explored candidate gene associations potentially related to these cognitive deficits, specifically looking at the association between these deficits and genes that have been implicated as playing a role in ADHD and COS (DAT1, DRD4, COMT, and 5HTT). Results. DAT1 and 5HTT were significantly associated with sentence span performance and WISC III Vocabulary and Block Design. COMT was significantly associated with sentence span, selective attention reaction time and WISC III vocabulary and block design. Discussion. ADHD and COS are both associated with weaknesses in multiple neurocognitive domains. The two disorders may be distinguished by greater weaknesses in selective attention specific to COS and greater weakness in response inhibition, when general intelligence is factored out, specific to ADHD. Case control analyses failed to find an association between ADHD diagnosis and any of our candidate genes. TDT analysis found significant associations between ADHD and DAT1 and DRD4. Preliminary analyses suggest DAT1, 5HTT and COMT may play a role in intelligence and working memory. COMT was also associated with selective attention. |
