Functional imaging, serotonin and the suicidal brain.

The involvement of the serotonergic system in the pathophysiology of suicidal behaviour has been established through indirect and direct research on serotonin and its metabolites and on serotonin transporters and receptors. Indirect research results include a reduced 5-HIAA in cerebrospinal fluid in violent suicide attempters and a blunted increase in prolactin after a fenfluramine challenge. Direct post-mortem research demonstrated an increase in 5-HT2A receptors. Direct in vivo functional imaging with PET or SPECT demonstrated a reduction in 5-HT2A binding index in suicide attempts in anxious and depressed suicide attempters and an increase in 5-HT2A binding in impulsive suicide attempters. These results are in keeping with 5-HT2A binding studies in depressed patients and impulsive animal research. Interestingly, both an increase and a decrease in 5-HT2A binding index seem to normalize with SSRI treatment.