BIMODAL DISTRIBUTION OF SERUM TRYPTOPHAN LEVEL

Serum levels of total L‐tryptophan (L‐TP) were determined before and during treatment in patients suffering from endogenous depression, who were treated with L‐TP, 6 g daily, and unilateral electro‐convulsive therapy (ECT). The gaussian curve of initial L‐TP concentrations changed into a bimodal distribution during treatment. The patients with initially lower L‐TP levels also had lower L‐TP levels during the treatment, thus forming the low‐concentration group within the bimodal distribution. In the patients with higher initial concentrations, the L‐TP levels increased to a much greater degree, forming the high‐concentration group. Patients in this group needed a larger number of ECT's, probably owing to L‐TP's property of shortening the seizure duration. No other background data or clinical variables showed significant differences between the groups. It is suggested that the bimodality of L‐TP levels is genetically determined. Copyright © 1979, Wiley Blackwell. All rights reserved