Association of Peripheral Pro-inflammatory Cytokines with Depressed Suicidal Patients: A Hospital-based, Cross-sectional Study

Background: Acute-phase reactants, such as C-reactive protein (CRP), along with pro-inflammatory cytokines like interleukin-6 (IL-6) and interleukin-1β (IL-1β), exhibit elevated levels in the peripheral bloodstream during acute mood episodes. In both major depressive disorder and bipolar disorder, instances of suicidal behavior, encompassing suicidal idealization and self-harm attempts, are linked to intensified depressive exacerbation. This study investigates the correlation between pro-inflammatory markers in patients experiencing major depressive episodes (MDE) with or without inclinations toward suicidal tendencies. Methods: The study comprised a sample of 75 outpatients categorized into three equally sized groups. These groups consisted of patients experiencing major depressive episodes with accompanying suicidal behavior, individuals undergoing MDE without any indications of suicidal tendencies, and a control group of mentally healthy individuals. Pertinent demographic information was gathered, and levels of pro-inflammatory markers, namely CRP, IL-6, and IL-1β, were quantified in the serum. The data were analyzed using the Statistical Package for the Social Sciences version 22. Results: Through bi variate analysis, it was observed that all three markers exhibited a noteworthy correlation with the subgroup experiencing MDE alongside suicidality (Pearson correlation coefficient ≤ 0.01). However, this correlation was not evident within the MDE subgroup lacking suicidal tendencies. Utilizing a one-sample t-test, it was established that both MDE groups displayed a substantial association (with a two-tailed significance level of ≤ 0.01) with the inflammatory biomarkers. Notably, the mean difference in biomarker levels was considerably more pronounced in the subgroup characterized by suicidality. Conclusion: Suicidal behavior, encompassing both ideation and attempts, exhibits an independent association with a pro-inflammatory state, irrespective of the severity of the linked depression. This relationship warrants further investigation to identify reliable biomarkers to enhance prediction and facilitate more effective management of suicidal behavior.