Studies of CSF 5-HIAA in depression and suicidal behaviour.

The present series of studies of CSF monoamine metabolites support the hypothesis of a role for serotonin in depressive illness, insofar that depressed patients have slightly lower CSF 5-HIAA concentrations than normal controls. Apparently a normal association between CSF 5-HIAA and platelet MAO activity is disrupted in depression. The importance of serotonin does not, however, appear to be confined to depressive illness. There is a strong association between a low CSF 5-HIAA and a tendency to suicidal behaviour, also outside the setting of depression. The nature of this relationship is unclear, but it is suggested that certain personality features may form a mediating link. A connection between a low serotonin turnover and a weakened control of aggressive or hostile impulses is one possibility.