P300 deficits in adults with attention deficit hyperactivity disorder: a meta-analysis.

BACKGROUND: The P300 (P3) event-related potential (ERP) component, a possible endophenotype for attention deficit hyperactivity disorder (ADHD), has been widely examined in children, but received little attention in adults. Our objective was to conduct a meta-analysis of P3 studies in adults with ADHD.
METHOD: We searched the Medline and PsycINFO databases for controlled studies examining both adult ADHD and matched healthy controls. Six relevant publications were identified for the meta-analysis, which had comparable data across studies with regard to the amplitude of ERP components related to target detection (P3, P3b). Pooled effect size (ES) for P3 amplitude as well as the association of the ES with age and gender were investigated using meta-regression.
RESULTS: Comparing the ADHD group versus controls, the pooled effect size for a decrease in P3 amplitude was in the medium range (Cohen's d=-0.55, p=0.0006). Additionally, meta-regression revealed that decrease in P3 amplitude significantly varied with the mean age of ADHD patients (p=0.0087), with a gradual increasing of the difference at higher ages. Results also showed a significant association between the ES and gender, indicating a more pronounced reduction of P3 amplitude in the ADHD group versus controls when females were predominantly represented in the sample.
CONCLUSIONS: To our knowledge, this is the first meta-analysis of P3 characteristics in adults with ADHD. It reveals a significantly decreased P3 amplitude during target detection. Our result that the reduction in P3 amplitude increases with age is interpreted in a neurodevelopmental context.