Mediating effect of inflammation on the relationship between sleep disruption and suicidal ideation in major depressive disorder

Sleep disruption, particularly insomnia, is a notable characteristic of depression and is associated with an increased risk of suicide in patients diagnosed with major depressive disorder (MDD). Moreover, the pathophysiology of depression and suicide has been linked to inflammation, specifically proinflammatory cytokines. However, the complex interplay among these factors in individuals with MDD remains poorly understood. This study investigated the mediating role of inflammatory cytokines in the relationship between sleep disruption and suicidal ideation (SI), with a particular emphasis on gender differences. This study used a cross-sectional design in which 281 individuals diagnosed with MDD were recruited from psychiatric clinics. The main assessments included the evaluation of sleep disruption, inflammatory markers, and SI. The Beck Scale for Suicide Ideation (SSI) scores was employed to quantify SI, whereas HAMD-SLD, a component of the Hamilton Rating Scale (HAMD-17), was used to evaluate sleep disruption. Blood analysis was performed to measure inflammatory markers. For females diagnosed with MDD, significant associations between sleep disruption and the levels of IL-6 (B = 0.994, p = 0.013) and TNF-α (B = 1.986, p = 0.016) were found when IL-6 or TNF-α were considered as mediators in the regression model. In addition, IL-6 (B = 5.689, p < 0.001) and TNF-α (B = 9.916, p = 0.006) exhibited strong correlation with SSI scores. The primary results of this study indicate that IL-6 and TNF-α could function as potential mediators in the relationship between sleep disruption and SI among female patients diagnosed with MDD. Name of the registry: Zhejiang University Trial registration number: ChiCTR1800017626 Date of registration: 2018-08-07, 'Retrospectively registered' URL of trial registry record: https://www.chictr.org.cn/showproj.html?proj=27321