Tryptophan depletion as a clinical tool: Current status and future directions.

The neurotransmitter serotonin (5-hydroxytryptamine, 5-HT) plays important roles in many basic functions: mood, feeding, anxiety, sleep, emesis, sexual function, thermoregulation, and cardiovascular tone. Over the past 10 years, tryptophan depletion (TD) studies of 5-HT function have emerged as an important clinical tool for studying brain serotonergic systems, and their relevance to practising psychiatrists has grown steadily. In this review, we discuss the evolution of TD studies and their continuing utility in understanding the role of 5-HT in psychiatric disorders and the development of more effective treatments.