CSF monoamine metabolites in patients and controls: support for a bimodal distribution in major affective disorders

The monoamine metabolites 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) in cerebrospinal fluid (CSF) were measured in 38 patients with major affective disorder and 48 age- and sex-matched controls by means of liquid chromatography. Statistical analysis using maximum likelihood normal mixture computations provided evidence for a subgroup of patients characterized by low CSF levels of both 5-HIAA and HVA. In controls, CSF 5-HIAA and HVA levels appeared to be normally distributed when fitted separately, whereas a subgroup of controls characterized by higher values of 5-HIAA and HVA could be discerned when metabolite data were fitted simultaneously. No relationship was found between monoamine levels and suicidal behaviour in patients. A statistically significant relationship was found between CSF 5-HIAA and HVA levels in patients and controls. These data provide supportive evidence for the existence of a subgroup of patients with an abnormal serotonin metabolism as reflected by 5-HIAA, and probably HVA, in CSF.