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.
Subject(s)
Affect , Attention Deficit Disorder with Hyperactivity , Diet Therapy/methods , Serotonin/biosynthesis , Tryptophan , Adult , Affect/drug effects , Affect/physiology , Attention Deficit Disorder with Hyperactivity/diagnosis , Attention Deficit Disorder with Hyperactivity/metabolism , Attention Deficit Disorder with Hyperactivity/psychology , Attention Deficit Disorder with Hyperactivity/therapy , Central Nervous System/metabolism , Cross-Over Studies , Double-Blind Method , Humans , Male , Psychological Techniques , Psychotropic Drugs/metabolism , Psychotropic Drugs/pharmacology , Reaction Time/drug effects , Sex Factors , Synaptic Transmission/drug effects , Synaptic Transmission/physiology , Treatment Outcome , Tryptophan/metabolism , Tryptophan/pharmacologyABSTRACT
OBJECTIVE: To date, the impact of the neurotransmitter serotonin (5-HT) on different neuropsychological functions in adults with attention deficit hyperactivity disorder (ADHD) is underinvestigated. We aimed to examine the effects of acute tryptophan depletion (ATD) and the resulting reduction in central nervous 5-HT synthesis on target/non-target discrimination ability and sustained attention in adults with ADHD using an AX-Continuous Performance Test (AX-CPT). METHOD: Twenty male patients with ADHD (age: M = 30.25 SD = 9.37) and twenty male healthy controls (age: M = 27.90 SD = 6.01) received ATD on one day and a tryptophan-balanced control condition (BAL) on another day in a double-blind within-subject crossover design. A continuous performance test (AX-CPT) with three conditions (AX, AY, and BX) was administered on both days under depleted and sham-depleted conditions. RESULTS: In patients omissions increased after ATD when compared with BAL. Patient's reaction time decreased after ATD when compared with BAL, which was contrasted by opposite effects in controls. Patients showed fewer correct responses (AX condition) and showed a higher rate of errors (condition AXE ) independent of ATD or BAL intake. CONCLUSION: The present preliminary results are indicative of the contribution of serotonergic neurotransmission to attentional processes in adults with ADHD.