Rapid visual information processing as a cognitive endophenotype of attention deficit hyperactivity disorder

Deficits in sustained attention and reaction time are core features of attention deficit hyperactivity disorder (ADHD). However, little is known about attention performance in unaffected siblings. Hence, we examined sustained attention and reaction time in youths with ADHD, unaffected siblings and controls to test whether impaired performance in attention tasks can be a potential endophenotype of ADHD.

We recruited 438 probands with clinical diagnosis of ADHD according to DSM-IV criteria, 180 unaffected siblings, and 173 healthy controls without lifetime ADHD. They were assessed using psychiatric interviews, Conners' Continuous Performance Test, and the tasks involving attention performance of the Cambridge Neuropsychological Test Automated Battery (CANTAB): Rapid Visual Information Processing (RVP), Reaction Time (RTI) and Match to Sample Visual Search (MTS). Multi-level models were used for data analysis.

Compared with the controls, probands with ADHD and unaffected siblings had significantly higher total misses, lower probability of hits in the RVP task and probands with ADHD performed worse in the RTI and MTS tasks after controlling for sex, age, co-morbidity, parental educational levels and IQ. The duration of methylphenidate use and IQ but not psychiatric co-morbidity or current use of methylphenidate were associated with deficits in sustained attention in probands with ADHD.

Our findings suggest that attention performance assessed by the RVP task, but not the RTI or MTS tasks, of the CANTAB may be a useful cognitive endophenotype for ADHD genetic studies.