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 ≥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