A test of the Interpersonal Theory of Suicide in a large community-based cohort

Background: Joiner's Interpersonal Theory of Suicide (Van Orden et al., 2010; Joiner, 2005) predicts that suicide ideation is strongest in those experiencing both high perceived burdensomeness and thwarted belongingness, and that the combination of suicide ideation and acquired capability for suicide is critical in the development of suicide plans and attempts. However, few datasets exist which allow the examination of these predictions. The present study aimed to test predictions from the model in a population-based cohort. Methods: a survey was completed by 6133 participants from the PATH Through Life Project. Scales measuring perceived burdensomeness, thwarted belongingness, hopelessness, capability to self-injure, ideation, plans and attempts were developed using existing items. Regression models were used to predict the outcomes of ideation and of plans/attempts. Results: consistent with the Interpersonal Theory, interactions were found between perceived burdensomeness and thwarted belongingness predicting ideation, and interactions of capability and ideation for plans/attempts. However, some predictions of the theory were not fulfilled. Nevertheless, the Interpersonal Theory explained more variance than epidemiological models using mental disorders as predictors. Age differences were evident, with models of older cohorts accounting for less variance. Gender models suggested thwarted belongingness was a stronger predictor of ideation in males than females. Limitations: while the fit of the factors assessing the Interpersonal Theory was adequate, the findings will need to be confirmed using previously developed scales of these constructs. Conclusions: predictive models of suicide need to take into account multiple risk factors, gender differences and changes in associations over the life span.