ABSTRACT
This chapter reviews the evidence supporting serotonergic dysfunction in depression, as well as treatment considerations. It deals with some of the serotonin-related pathways which are known, as well as some of the measures used to quantify serotonin function. The biochemistry of tryptophan, serotonin, and 5-hydroxyindoleacetic acid (5-HIAA) is more complex than this rather simplistic overview. The chapter also reviews the major findings of serotonin dysfunction in a subset of depressive illness. It considers that heterogeneity of serotonin dysfunction may exist even in this subset of major depressive illness. The chapter describes how blood platelet serotonin uptake has been used as a model for serotonergic neuronal reuptake. Abnormal serotonin function was first implicated in depressive illness as early as 1960 with the discovery of low cerebrospinal fluid 5-HIAA in depressed patients. The use of serotonin measures to specify the choice of antidepressant is a critical clinical issue which requires further investigation.
