Pro-inflammatory cytokines level in depressed patients with suicidal behaviour: a systematic review and meta-analysis

The study assesses proinflammatory factors in major depressive disorder (MDD) patients with and without suicidal behaviors, and healthy controls, to identify potential biomarkers for suicidal behaviors and prevention strategies.

We conducted a systematic review, which we have registered in Prospero (#CRD42024547764), and searched through five databases until March 2024. We included observational studies in English that reported on depressed patients with and without suicidal behaviors, as well as healthy controls, and measured the levels of pro-inflammatory cytokines. The Newcastle- Ottawa Scale was used for quality evaluation of the studies and the main analysis was performed using Stata 17.

One systematic review resulted in 4,369 articles but only 24 were selected for the review. The meta-analysis showed depressed patients with suicidal behaviors had significantly higher interleukin (IL)-6 levels compared to the control group with a standardized mean difference (SMD) of 1.26 [0.07, 2.45]; I² = 98.81%. There was no significant difference noted between the depressed patients suffering from suicidal behaviors and those not suffering (SMD 0.42 [-0.58, 1.42]; I² = 98.50%). There is no significant difference between the groups in the levels of tumor necrosis factor-alpha (TNF-α) and IL-10. Further analysis of IL-4, IL-2, IL-1β, IF-γ, and TGF-β1 also indicated no significant group differences.

The review found no significant cytokine differences (including IFN-γ, IL-1β, IL-2, IL-4, IL-8, IL-10, TGF-β1, TNF-α) between depressed individuals with or without suicidal ideation and controls. Variations likely reflect methodological differences, highlighting the need for standardized, longitudinal research.