Abnormalities of serotonin metabolism and nonpsychotic psychiatric disorders.

Abnormalities of brain serotonin (5-hydroxytryptamine; 5-HT) metabolism have been proposed as the neurobiological basis of a vulnerability to depression and of a long-standing tendency toward impulsivity and aggression. Results from studies that have employed a variety of 5-HT measures, including the assessment of cerebrospinal fluid 5-hydroxyindoleacetic acid concentrations, 5-HT uptake site densities, and 5-HT2 receptor densities in brain tissue and on platelets, and prolactin increases following fenfluramine administration, provide support for these two hypotheses. The goal of future research should be to better define the pathophysiological role of 5-HT dysfunction for both mood instability and impulsivity, in the service of developing improved treatments for these psychopathological conditions.