The Role of Gene Polymorphisms, and Analysis of Peripheral and Central Levels of Interleukins in Suicidal Behavior: A Systematic Review

In terms of the physiological characteristics of suicidal behavior (SB) disorder, an increase inflammation response has been reported in these individuals. Therefore, the pro-inflammatory and anti-inflammatory activities of interleukins are adequate markers to research in order to understand the pathogenesis of SB. For that reason, the aim of this systematic review was to evaluate the role of interleukins in individuals with suicidal behavior disorder. A systematic search was performed in PubMed, Scopus and EBSCO databases up to July 2019. We used the words "interleukin" AND "suicide", "interleukin" AND "suicidal", and "IL-". Articles where interleukins concentrations were measured in individuals with SB and/or genetic studies addressing interleukins genes variants as possible markers to SB were included. A total of 54 articles were included. Articles that measured interleukin levels comprised 1111 cases and 1588 controls; whereas the genetic studies comprised 3082 cases and 5148 controls. These studies evaluated the concentrations of IL-1β, IL-2, IL-3, IL-4, IL-5, IL-6, IL-8, IL-10, sIL-2R in serum, plasma. The pro-inflammatory interleukins concentrations were higher in cases than in controls; however, we observed heterogeneity in the measurements and sample sources. Whereas, 9 polymorphisms of IL-1α, IL-1β, IL-6, IL-1β-8 genes were analyzed in association with suicide behavior disorder, though no conclusive outcomes were attained. Our results suggest that individuals with suicide risk undergo continuous stress that could trigger the release and circulation of pro-inflammatory interleukins and therefore their concentration in plasma. However, more studies are necessary in order to reach conclusively outcomes.