A meta-analysis of cytokines in suicidal behavior

Background: We conducted the first meta-analysis of studies comparing the plasma and CSF concentrations of cytokines in suicidal patients vs. non-suicidal patients or healthy controls. Methods: We searched Medline, Web of Science, and PsycINFO from 1965 to November 2014 for relevant studies. Manual searches of references and unpublished data were also included. Suicidal patients included severe suicide ideators and suicide attempters. Results: Eleven articles were available for the meta-analysis, for a total sample size of 494 suicidal patients, 497 non-suicidal patients and 398 healthy controls. Levels of 6 independent plasma cytokines (IL2, IL6, TNFalpha, IFNgamma, IL4, TGFbeta) were meta-analyzed for plasma studies comparing suicidal vs. both controls. IL8 level was meta-analyzed for cerebrospinal fluid studies comparing suicidal patients with healthy controls. We reported with medium effect size, that suicidal patients had: (1) lower IL2 plasma levels than both non-suicidal patients and healthy controls (medium effect size); (2) lower IL4 and higher TGFbeta plasma levels than healthy controls. Conclusion: Our results promote the hypothesis of altered inflammatory markers in suicidal patients, for both pro-inflammatory (IL2) and anti-inflammatory (IL4 and TGFbeta) cytokines.