Tryptophan depletion in SSRi-recovered depressed outpatients

Rationale: Recently, a number of studies have challenged the finding that a cute tryptophan depletion (TD) increases depressive symptoms in medicated, formerly depressed patients. The present study examined the effects of acut e nutritional TD on remitted depressed patients currently treated with sele ctive serotonin reuptake inhibitors. In an attempt to clarify conflicting e arlier findings, the effects of a number of clinical variables on outcome w ere also investigated. Methods: Ten patients underwent TD in a double-blind , controlled, balanced crossover fashion. The control session followed the procedure of Krahn et al. (1996 Neuropsychopharmacology 15:325-328). Sessio ns were 5-8 days apart. Results: TD was significantly related to increased scores on clinician-rated depression and anxiety scales, and on self-rated depression, anxiety, and somatic symptoms. The control challenge had no eff ect, despite the fact that the reductions in plasma tryptophan during the c entral session were unexpectedly high. Some evidence was found for a thresh old in the relationship between reduction of plasma tryptophan and mood res ponse. Conclusions: The mood effect of TD in medicated, formerly depressed patients was confirmed. A threshold may exist for mood effects following TD , implying that recent negative findings may have been caused by insufficie nt depletion. No other predicting or mediating factors were identified, alt hough the variable "history of response pattern, to medication" deserves fu rther study.