Peripheral BDNF levels in psychiatric patients with and without a history of suicide attempt: A systematic review and meta-analysis

Objective Psychiatric patients are at increased risk of attempting suicide. Several potential biomarkers of suicide risk have been proposed, with inconsistent findings. The present paper aimed to evaluate differences in peripheral BDNF levels between psychiatric patients with and without a history of suicide attempts. Methods We conducted a systematic review and meta-analysis. Relevant papers published up to January 5, 2021 were identified searching the electronic databases Web of KnowledgeSM (including Web of Science, MEDLINE®, KCI - Korean Journal Database, Russian Science Citation Index, and SciELO Citation Index) and PsycINFO. A random-effect meta-analysis was conducted using Stata 16. Results Thirteen studies met inclusion criteria. Overall, no significant differences in BDNF levels between the two groups were found (13 studies, n = 1340, Hedge's g = -0.21, 95% CI -0.44 to 0.02). Heterogeneity was substantial (I2 = 72.91%). Subgroup analyses revealed that BDNF levels were significantly reduced in plasma with medium effect size (5 studies, n = 363, Hedge's g = -0.44, 95% CI -0.86 to -0.02), but not in serum (8 studies, n = 977, Hedge's g = -0.09, 95% CI -0.33 to 0.15). No significant differences were found according to the type of diagnosis (major depressive disorder vs. other diagnoses) or the time of suicide attempt (lifetime vs. recent). Conclusion The utility of BDNF as a biomarker of suicide attempts in psychiatric patients appears limited to its plasma concentration. Although caution interpretation is needed, our findings may represent a starting point for the design of rigorous case-control studies exploring the association between neurotrophins and suicidal behaviors.