Longitudinal Association between Stressful Life Events and Suicidal Ideation in Adults with Major Depression Disorder: The Mediating Effects of Insomnia Symptom

Background: Stressful life events (SLEs) and suicidal ideation (SI) are prevalent in persons with major depression disorder (MDD). Less is known about the underlying role of insomnia symptoms in the association between SLEs and SI. This study sought to investigate the longitudinal association among SLEs, insomnia symptoms and SI in persons with MDD. Methods: This three-wave prospective study used data collected between December 2020 and September 2022 from the Depression Cohort in China (DCC), which is a large, ongoing cohort study targeting at persons aged 18-64 years with MDD. The study population included 511 persons with MDD (mean [SD] age, 28.7 [6.7] years, 67.1% were females). A structured questionnaire and validated scales were utilized to assess the cumulative numbers and multiple types of SLEs, insomnia symptoms and SI. Generalized estimated equation (GEE) was utilized to explore prospective association among exposure of SLEs, insomnia symptoms and SI. Besides, the structural equation model (SEM) was performed to estimate the longitudinal mediating effect of insomnia symptoms in the relationship between SLEs and SI. Results: After adjusting for control variables, three or more SLEs (adjusted β estimate = 1.299, 95% CI=1.016-1.662) and childhood physical abuse (adjusted β estimate = 1.301, 95% CI=1.020-1.658) were related to an elevated risk of SI. Additionally, the association between SLEs and SI was significantly mediated by insomnia symptoms (standardized β estimate = 0.026, 95% CI = 0.003 - 0.053). Conclusions: Cumulative SLEs were determined to be longitudinally associated with SI in persons with MDD. We further observed that insomnia symptoms were highly associated with SLEs and SI. Clinicians assessing persons with MDD, especially with history of SLE and insomnia symptoms, should carefully evaluate for the presence of suicidality as part of a personalized assessment of their depressive illness.