Abnormalities in the serotoninergic system have been associated with suicidality, aggression, and impulsivity. Exactly what role serotonin plays in the initiation, modulation, maintenance, or regulation of such behaviours remains under study. However, recent data suggest that serotonin is involved along the pathway from genetic predisposition and environmental stimulus to expression of psychiatric disorders and suicidal behaviour.

On the other hand, it has been suggested that the seemingly “robust” association of low CSF-5HIAA concentration with suicidality and aggression is rather weak, and are likely to represent somewhat premature translations of findings from studies that have flaws in methodology.

Finally, we the review the controversial role of the selective serotonin reuptake inhibitors (SSRI) on suicidality, as they have been suggested: i) to decrease suicide rates in the population, and ii) to increase suicide rates in some individuals in early treatment.