COMT and attention deficit-hyperactivity disorder: COMT Val158Met did not directly predict aggression (mean score for Val allele carriers 1.2 (SD 1.4) versus 1.1 (SD 1.3); p = .83) or conduct disorder (mean conduct score for Val allele carriers 3.5 (SD 3.1) versus 3.3 (SD 2.8); p = .73; 48.6 % with CD diagnosis in Val allele carriers, p = .73) in this sample in contrast to the original total larger genotyped ADHD sample from which the participants were drawn.