Cannabis use and suicidal ideation: Test of the utility of the interpersonal-psychological theory of suicide

Despite a documented relationship between cannabis use and suicidality, little is known about psychological vulnerability factors that may increase suicidality among this high-risk group. The Interpersonal-Psychological Theory of Suicide (IPTS; Joiner, 2005) proposes that people are vulnerable to wanting to die by suicide if they experience both perceived burdensomeness and thwarted belongingness. Daily cannabis users may be especially vulnerable to these factors. The current study used moderated mediation to test whether the relation between daily cannabis use status and suicidal ideation (SI) occurred indirectly via higher levels of both perceived burdensomeness and thwarted belongingness among 209 (76.1% female) current cannabis using undergraduates who used cannabis daily (n=39) or less frequently (n=160). The direct effect of cannabis use status on SI was no longer significant after controlling for thwarted belongingness, perceived burdensomeness, and the thwarted belongingness X perceived burdensomeness interaction. Cannabis use status was predictive of greater SI indirectly through perceived burdensomeness only at higher levels of thwarted belongingness. Findings support the utility of the IPTS in regard to SI among daily cannabis users, indicating that difficulties in interpersonal functioning may serve as potential pathways through which daily cannabis use may lead to greater suicide risk.