1. ¹Department of Psychiatry, Vanderbilt University School of Medicine, Nashville, TN, USA
2. ²Department of Psychiatry, Indiana University School of Medicine, Indianapolis, IN, USA
3. ³Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, TN, USA

Correspondence: Dr RM Salomon, Department of Psychiatry, Vanderbilt University School of Medicine, 1500 21st Avenue South, VAV 2200, Nashville, TN 37212, USA. Fax: +1 615 343 9038; E-mail: ron.salomon@vanderbilt.edu

Received 25 January 2002; Revised 31 July 2002; Accepted 18 October 2002; Published online 19 March 2003.

Abstract

This work studies association between relapse during acute tryptophan depletion (ATD) and CSF level of tryptophan (TRP) in remitted depressives treated with sertraline or bupropion. Eight medication-responding depressives ingested an ATD amino acid mixture during 48-h continuous CSF sampling before and after treatment. Mood rating scores were compared with nadir levels of TRP in CSF. CSF TRP nadirs averaged 8.7% of am baselines in remitted patients. Mood relapsed whenever the CSF nadir was below 40 nmol/l TRP in remitted patients, and never when above (Fisher's exact test, P=0.029). Relapsing medication responders also showed very low preantidepressant ATD-induced nadirs. ATD-induced relapses were associated with low CSF TRP levels. Individual susceptibility to depletion may be independent of antidepressant treatment, mood state, or treatment status. Resistance to relapse may invoke an undefined, protective CNS mechanism against extremely low CSF levels of TRP during ATD.