Serotonergic function accounts for a variety of conducts, including aggressive and impulsive behavior. Zepf et al (2008, Human Psychopharmacology) explored the effects of ATD and the subsequent reduction of brain 5-HT synthesis on behavioral inhibition in passive avoidance learning assessed in a computerized go/no-go task in 22 male patients four hours after ingestion of ATD/BAL. Highly hostile aggressive patients showed increased inhibition errors under ATD whereas low hostile aggressive patients showed lower rates of inhibition errors, making for a better performance under ATD. These results suggest that in ADHD levels of trait-aggressive characteristics influence the susceptibility to changed behavioral inhibition after an acute 5-HT dysfunction.