The effects of tryptophan depletion on mood and psychiatric symptoms

Background: The number of studies using tryptophan depletion (TD) challenge has increased markedly in the past few years. Recently, a number or negati ve results have been published, implicating that the effect of TD on mood m ay be less consistent than previously thought. Methods: The literature on t he mood effects of TD in psychiatric patients and healthy volunteers was re viewed. Results: TD has a mood-lowering effect in subgroups of recovered de pressed patients, patients with seasonal affective disorder and vulnerable healthy subjects. The mood effect in former patients is of a different qual ity, however, than the effect in healthy subjects. Some recent negative stu dies in depression might be explained by insufficient lowering of plasma tr yptophan levels. Preliminary evidence exists for an effect of TD on bulimia nervosa, autism, aggression and substance dependence. Conclusions: The eff ects of TD on mood may be more consistent than suggested by a number of rec ent negative studies. Response to TD in recovered depressed patients is ass ociated with prior treatment. However, even in SSRI-treated patients the re lapse rates are not higher than 50-60%, which needs to be explained. The cl inical usefulness of the response to TD in recovered patients (prediction o f relapse after treatment discontinuation) and in symptomatic patients (pre diction of treatment refactoriness) deserves more research attention. Furth er suggestions for future research include the cognitive effects of TD in r ecovered depressed patients and the effect of dietary habits on response to TD. (C) 2001 Elsevier Science B;V. All rights reserved.