Diminished 5-HT functioning in CBCL pediatric bipolar disorder-profiled ADHD patients versus normal ADHD: susceptibility to rapid tryptophan depletion influences reaction time performance

Objective There is a current debate on characterizing children with pediatric bipolar disorder (PBD) through a profile within the child behaviour checklist (CBCL), and on the involvement of the 5‐HT system in the underlying neurobiological processes of PBD. The aim of the present paper was to investigate reaction time performance in patients with CBCL‐PBD and to discriminate ADHD from ADHD with CBCL‐PBD with respect to diminished 5‐HT functioning and reaction time. Methods Twenty‐two patients with ADHD received the rapid tryptophan depletion test (RTD) thus lowering the central‐nervous 5‐HT synthesis rate within a placebo‐controlled double‐blind within‐subject crossover design. Reaction time was assessed using a competitive reaction time game with low and high provocation after both depletion and placebo intake. The study sample was divided into high and low scorers according to their CBCL‐PBD scores. Results Comparing those six patients with the highest and clinically significant CBCL‐PBD scores versus those six patients with the lowest, patients with a high CBCL‐PBD score showed a slower reaction time under RTD compared to patients with low CBCL‐PBD scores after high provocation. CBCL‐‘aggression’ discriminated between the two groups. Conclusions The results suggest alterations in 5‐HT functioning in CBCL‐PBD‐spectrum patients, and ‘aggression’ as a potential moderator variable to ADHD. Copyright © 2008 John Wiley & Sons, Ltd.