No clear effects of acute tryptophan depletion on processing affective prosody in male adults with ADHD.

ABSTRACT

OBJECTIVE: Adults with attention deficit hyperactivity disorder (ADHD) have difficulties processing affective prosody, and research evidence demonstrates the importance of brain serotonin (5-HT) in the neurobiology of ADHD. This study aimed to investigate whether diminished brain 5-HT synthesis, as achieved by acute tryptophan depletion (ATD), can impair the processing of affective prosody in adults with ADHD. METHOD: Twenty male patients with ADHD and twenty male healthy controls received ATD and a tryptophan-balanced control condition on separate days in a double-blind within-subject repeated measures crossover design. In both conditions, the Tübingen Affect Battery was administered in which subjects had to name the affective prosody of sentences with neutral, congruent, or incongruent semantic content. RESULTS: Participants in the group of patients with ADHD perceived affective prosody less accurately than controls. Participants with ADHD showed compromised processing of sentences, committing more errors than healthy controls when identifying affect in instances of incongruent semantic content (P = 0.031). ATD did not contribute to this effect (all P > 0.5). CONCLUSION: The difficulties male adults with ADHD have in accurately processing affective prosody may result from impairments in their ability to inhibit unwanted stimuli and impulses. No clear evidence implicates 5-HT as a cause of these impairments.