Diminished central nervous 5-HT neurotransmission and mood self-ratings in children and adolescents with ADHD: no clear effect of rapid tryptophan depletion.

Introduction: Research on 5-HT-functioning in adult patients and healthy subjects using rapid tryptophan depletion (RTD) has indicated weak but stable effects on mood ratings. Altered mood in children and adolescents with attention-deficit/hyperactivity disorder (ADHD) can confound the differential diagnosis between severe ADHD and mood disorders such as pediatric bipolar disorder. The present study investigated the effects of RTD induced lowered central nervous 5-HT-levels on mood self-ratings in children with ADHD.

Methods: Seventeen boys with ADHD participated in the study in a double-blind within-subject crossover-design. They were administered RTD within an amino acid drink lacking tryptophan, thus lowering central nervous 5-HT-synthesis. On another day they received a placebo. Self-rated mood was assessed on both days at baseline conditions and at three different post-drink time-points.

Results: RTD had no clear effect on mood within the whole sample. Low scorers on venturesomeness were more strongly affected by RTD in terms of feelings of inactivity and negative feelings compared to high venture patients.

Conclusions: Our data did not show a significant effect of RTD on mood self-ratings. However, the findings must be considered as preliminary and require further replication, in particular as they could be due to sampling bias.