Higher Interleukin 13 differentiates patients with a positive history of suicide attempts in major depressive disorder

Abstract

Background: Every 40 seconds one person dies from suicide worldwide, half of which are related to depression. Neuroinflammation has been reported in neuropsychiatric conditions, including major depressive disorder (MDD). Preliminary findings suggested a link between inflammation and suicidal behavior. Nevertheless, to the best of our knowledge, no previous study explored how a wide range of cytokines may differentiate lifetime suicidal behaviors (i.e. positive history of suicide attempts) in patients affected by MDD. Methods: In 28 healthy controls (HC), 28 MDD patients with a positive history of attempting suicide (SA), and 28 MDD patients with a negative history (nSA), we determined concentrations of immune analytes using an ultra-sensitive Pro Human Cytokine Group 27-Plex Panel and Chemokine immunoassay panels (Bioplex). To deal with the 27 highly correlated cytokines we applied two different statistical approaches that reduce the dimensionality of data: Principal Component Analysis, exploring if suicidality may be related to a comprehensive derived inflammatory state, and elastic-net penalized regression that allows considering as predictor every single cytokine. Results: Five inflammatory components were identified: none predicted suicidal behavior. Elastic net results prompted IL-13 as a new candidate marker of suicide in patients with MDD. Limitation: The retrospective design of the study and the small sample size preclude the possible causal interpretation and generalizability of reported results. Conclusion: Exploring a wide range of cytokines may provide a new inflammatory signature of suicide useful for understanding pathophysiological underpinnings, developing new therapeutic targets, and allowing the identification of at-risk factors.