Serotonergic functioning and trait-impulsivity in attention-deficit/hyperactivity-disordered boys (ADHD): influence of rapid tryptophan depletion.

Objective: The present study investigated the effects of rapid tryptophan depletion (RTD) and the ensuing reduction of central nervous levels of serotonin (5-HT) on reactive aggression with respect to personality factors comprising aspects of trait-impulsivity and -aggression in boys with attention-deficit/hyperactivity-disorder (ADHD).

Methods: Twenty-two male adolescent patients with ADHD received the RTD test on one day, and, on another day a tryptophan balanced placebo in a double-blind within-subject crossover design. Impulsive personality factors and trait-impulsivity were assessed in advance of the study. Aggression was provoked using a competitive reaction time game 270 min after RTD/placebo intake.

Results: RTD had a significant effect on increased aggressive behaviour with which low-grade impulsive patients responded. High-grade impulsive patients were not affected by RTD or even responded with increased aggressive behaviour while receiving placebo treatment.

Conclusions: The present study supports the hypothesis that 5-HT functioning in ADHD patients influences reactive aggression depending on aspects of trait-impulsivity. Future studies are necessary in order to detect the specific influence of ADHD as regards the relevance to 5-HT-induced changed aggressive responding.