Tryptophan depletion and risk of depression relapse: a prospective study of tryptophan depletion as a potential predictor of depressive episodes.

BACKGROUND This study investigated the relationship between depressive symptom response during tryptophan depletion and future depressive episodes. METHODS Twelve subjects with prior major depressive episodes in remission and medication-free for > or =3 months (patients), and 12 matched healthy (control) subjects received two tryptophan depletion tests 1 week apart. During follow-up the Hamilton Depression Rating Scale was administered weekly for 1 month, monthly for 3 months, and once at 6 and 12 months. RESULTS With results from both tests, tryptophan depletion has a sensitivity of 78%, specificity of 80%, positive predictive value of 70%, and negative predictive value of 86% to identify future depressive episodes. Survival analysis shows that mood response to tryptophan depletion reliably predicts major depressive episodes during the follow-up year (r =.2725, p =.014). CONCLUSIONS Tryptophan depletion may be clinically useful in identifying individuals at risk for future major depressive episodes.