Objective: Building on literature that measured the association between social network strain (SNS) and suicidal ideation using conventional regression analyses, we examined the effect of SNS, due to adverse childhood experiences (ACEs), on suicidal ideation using instrumental variables (IV) to eliminate the potential biases that may have occurred in earlier studies due to residual confounding.
Methods: This retrospective cohort study linked longitudinal data from the National Survey of Midlife Development in the United States (MIDUS) Refresher Biomarker Project (2012-2016), the MIDUS Refresher Project (2011-2014), the MIDUS 2 Biomarker Project (2004-2009), and the MIDUS 2 Project (2004-2006). Participants completed a phone interview, self-administered survey, and biomarker data collection. Exposure indicators included self-reported suicidal ideation, ACEs, and SNS from family, spouse, and friends. IV analysis was used to evaluate the continuous local average treatment effect of SNS on suicidal ideation when SNS only varied due to variation in ACEs.
Results: Our sample included 1703 middle-aged adults (52.9% females), which were followed up for 12 years. An IV probit model controlling for sociodemographic characteristics found a one-standard-deviation reduction in SNS reduced suicidal ideation by 22.6% (p < 0.01). A comprehensively controlled IV probit model found that a one-standard-deviation reduction in SNS is associated with a 21.4% (p = 0.05) decrease in suicidal ideation.
Conclusions: The causal pathway from SNS (due to ACEs) to suicidal ideation among middle-aged adults was established using IV analysis in this large-scale longitudinal study. The magnitude of this effect is sufficient to warrant the development of programs to improve social network relationships among family, friends, and spouses/partners. Suicide prevention programs addressing SNS may significantly reduce suicidal ideation among middle-aged Americans who have experienced ACEs.