A longitudinal test of the predictions of the interpersonal-psychological theory of suicidal behaviour for passive and active suicidal ideation in a large community-based cohort

Background: The Interpersonal-Psychological Theory of Suicide (IPTS) aims to elucidate the key antecedents of suicide deaths. Limited research has tested the IPTS in a community setting, and very little longitudinal research has been conducted. The current study longitudinally tested the predictions of the IPTS for suicidal ideation in a large population-based sample. Methods: The PATH through Life study assesses three age cohorts (20's, 40's, 60's) every four years. Two interpersonal factors were estimated at the third wave of assessment: thwarted belongingness (TB) and perceived burdensomeness (PB). The roles of these factors in suicide ideation (active and passive) four years later were estimated using logistic regression models (n = 4545). Results: A one SD increase in TB was associated with increased odds of 37% for passive ideation and 24% for active ideation. For PB, odds were increased 2.5-fold for passive ideation and 2.4-fold for active ideation. A significant negative PB x TB interaction was found for passive but not active ideation. Effects were not consistent by age group or gender. Limitations: Proxy measures were used to assess the constructs. The extended timeframe and low prevalence of suicidal ideation limited power to find effects within subgroups. Conclusions: Although TB and PB were individually associated with suicidal thoughts, little evidence was found for the key predictions of the IPTS longitudinally. Further investigation of the dynamic interplay between interpersonal factors over time is needed.