Tryptophan depletion: a predictor of future depressive episodes in seasonal affective disorder?

Patients with seasonal affective disorder (SAD) do not necessarily experien ce depressive episodes every winter. We assessed whether the behavioural re sponse to tryptophan depletion in summer when patients are fully remitted a nd off therapy is capable of predicting a future depressive episode of SAD. In a prospective study design, we followed up 11 consenting SAD patients w ho had undergone tryptophan depletion during summer. We evaluated how many of these patients would develop a depressive episode in the subsequent fall /winter. Seven out of eight patients who relapsed during tryptophan depleti on in summer developed a depressive episode in the subsequent winter. Two o ut of the three patients who did not relapse during tryptophan depletion re mained well during the follow-up period. Our preliminary findings suggest t hat those SAD patients who develop depressive symptoms during tryptophan de pletion when they are fully remitted and off therapy remain at high risk to experience a depressive episode of SAD also in the subsequent winter. Int Clin Psychopharmacol 14:313-315 (C) 1999 Lippincott Williams & Wilkins.