Reduced platelet serotonin in depression.

Platelet serotonin levels were measured in several psychiatric disorders to determine whether they distinguish among major depressive disorder (one or more depressive episodes and no manic episodes), dysthymic disorder (depressive neurosis), and schizophrenic and paranoid disorders. Serotonin levels in 141 subjects were determined using high performance liquid chromatography with electrochemical detection. Serotonin (5HT) levels in control subjects were significantly lower in males than in females. A marked reduction in 5HT levels, as compared to controls, was found in male and female patients with major depressive disorder, but not in dysthymic disorder. A slight but significant reduction in serotonin levels was found in female schizophrenic patients. The reduction in serotonin levels found in major depressive disorder could not be attributed to chronic antidepressant treatment. Liquid chromatography with electrochemical detection used in the present study permits a large-scale investigation.