COMT and attention deficit-hyperactivity disorder: We based our hypothesis on former reports concerning the influence of COMT on antisocial behavior in ADHD patients (Thapar et al., 2005a; Caspi et al., 2008) and possible mediating effects (Langley et al., 2010; van Goozen et al., 2016) and thus chose to only investigate COMT effects in this context.