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 following the PRISMA guidelines. Relevant papers published up to January 5, 2021 were identified searching the electronic databases Web of Knowledge^SM 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 period 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.