The role of inflammatory cytokines in suicidal behavior: A systematic review

There is growing evidence that inflammatory mediators play a critical role in the pathophysiology of both major depression and suicidal behavior. Immunological differences have been reported in both major affective disorders and suicidal behavior. Specifically, increased levels of pro-inflammatory cytokines have been shown to correlate with the severity of depression and various cytokines have been identified as potentially important in understanding the pathophysiology of major affective disorders/suicidality. We aimed to conduct a systematic review of the current literature to investigate the association between inflammatory cytokines and suicidal behavior. Only articles from peer-reviewed journals were selected for inclusion in the present review. Most studies documented the association between suicidality and IL2, IL-6, IL-8, TNF-alpha and VEGF levels that have been found altered in suicidal behavior. The presence of major depressive disorder (MDD) with suicidal ideation/attempts was associated with differences in inflammatory cytokine profile when compared to that without suicidal ideation/attempts. Most suicide attempters or subjects with suicidal ideation showed an imbalance of the immune system but this does not imply the existence of a causal link. Also, not all studies demonstrated a positive correlation between inflammatory cytokines and suicidal behavior. Further additional studies should elucidate the molecular mechanisms of the immune activation pathways underlying suicidality. (C) 2013 Elsevier B.V. and ECNP. All rights reserved.