Platelet and Plasma Serotonin Levels and Platelet Monoamine Oxidase Activity in Patients with Major Depression: Effects of Sertraline Treatment

Objectives: The purpose of this study was to investigate platelet and plasma serotonin levels and platelet monoamine oxidase activity in patients with major depression and the influence of sertraline treatment on these biochemical measures. Methods: Twenty-one patients with major depression and 21 healthy controls matched for age, sex, and smoking status were recruited. Platelet and plasma serotonin levels and platelet monoamine oxidase activity were assessed after a one-week drug-free interval (baseline) and six weeks after the initiation of sertraline treatment. Results: At baseline, the plasma serotonin levels were lower and platelet serotonin and monoamine oxidase levels were higher in the patient group compared to the controls. After six weeks of sertraline treatment, platelet serotonin and monoamine oxidase levels had decreased and plasma serotonin levels had increased, all approaching the levels in the controls. Conclusions: Our results support some earlier findings indicating that major depressive patients have higher platelet serotonin levels and monoamine oxidase activity and lower plasma serotonin levels as compared with healthy subjects. Additionally, these abnormal parameters seem to normalize during sertraline treatment. However, in contrast to the results of some previous studies, our findings suggest that these biochemical parameters are not useful for predicting the clinical response rate or time (i.e. early and late responder) to a selective serotonin reuptake inhibitor, sertraline.