Serafini G, Pompili M, Lindqvist D, Dwivedi Y, Girardi P. The role of neuropeptides in suicidal behavior: a systematic review. Biomed Res Int. 2013;2013:687575. 

Neuropeptides are small protein-like substances, which are produced and released by neurons through the regulated secretory route and act on neural substrates. They function like signaling molecules and are involved in regulating vast array of physiological functions.

There is a growing body of evidence which suggests that neuropeptides may be involved in the pathophysiology of suicidal behavior. A critical review of the literature was conducted to investigate the association between neuropeptides and suicidal behavior. Most studies show an association between suicidality and neuropeptides such as corticotropin-releasing factor (CRF), VGF, cholecystokinin, substance P, and neuropeptide Y (NPY), which have been demonstrated to act as key neuromodulators of emotional processing. Significant differences in these neuropeptides levels have been found in those people who have attempted or completed suicide compared with healthy controls or those dying from other causes.

The implications of the changes in these neuropeptides in suicidal people are discussed in this review paper.