Tryptophan Depletion in Stable Lithium-Treated Patients With Bipolar Disorder in Remission-Reply

In reply Benkelfat and colleagues report the lack of behavioral effect of tryptophan depletion in stable bipolar patients in clinical remission (1 to 4 years) receiving lithium monotherapy. The authors contrast their results to our first report of tryptophan depletion in recently remitted (2 to 4 weeks) depressed patients. They point out significant differences between our studies: the differing lengths of remission, the lithium monotherapy, and the differences in diagnosis and gender, as well as the possibility that the duration of plasma tryptophan depletion may be too brief to affect mood stability in these patients. The authors conclude that the therapeutic effects of long-term lithiumtherapy may not depend primarily on 5-HT availability in the central nervous system. We generally agree with the explanations suggested by Benkelfat et al, and especially concur with the conclusion that short-term fluctuations in 5-HT availability may not disrupt affective state in euthymic, stable, lithiummaintained patients with