Neurotrophin levels in postmortem brains of suicide victims and the effects of antemortem diagnosis and psychotropic drugs.

Suicide is a major public health problem but the neurobiological factors of risk are poorly understood. Recent studies have mentioned changes in the serotoninergic system and in neuronal plasticity, as well. The present investigation was undertaken to examine whether there is an abnormality in brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) proteins in suicide victims. The effect of diagnosis and drug treatments on the neurotrophins was also assessed. Thirty suicide victims (11 F/19 M) and twenty-four (10 F/14 M) drug-free non-suicide subjects, devoid of psychiatric or neurological disease, were examined. Antemortem diagnoses and toxicological analyses had been performed. The ventral prefrontal cortex (PFC), the hippocampus, and the entorhinal cortex were selected. BDNF and NT-3 levels were assayed either with the Western blot or with the ELISA method. Results indicated a significant decrease in BDNF and NT-3 levels in the hippocampus and PFC (only BDNF) but not in the entorhinal cortex, of suicide victims who were drug-free compared with non-suicide controls. The decrease was observed in all suicide victims, regardless of diagnosis. In drug-treated suicide victims, neurotrophin levels were not significantly different from non-suicide controls. This study supports a role of BDNF and NT-3 neurotrophin, in the pathophysiology of suicidal behavior. Anatomically, this role may implicate the hippocampus and the PFC but not the entorhinal cortex. The absence of change in BDNF and NT-3 levels of drug-treated suicide victims suggests that both neurotrophins are mediators of psychotropic drugs. A better understanding of the neurobiology of suicide could help detect populations at risk.