A test of self-medication hypothesis for drug use in homeless persons: the role of severe mental illness

The purpose of this study was to test the self-medication hypothesis of drug use in a sample of homeless persons. A serial mediation model was tested to examine the effects of recent victimization on trauma-related symptom severity, and the effects of trauma-related symptom severity on severity of severe mental illness (SMI) symptoms, and finally the effects of severity of SMI symptoms on illicit drug use. The final sample for the study included 164 participants who were assessed prospectively at both baseline and 6-month post-baseline. It was hypothesized that SMI would mediate the pathways for self-medication. Structural Equations Modelling analyses revealed that current trauma-related symptom severity mediated the relationship between recent victimization and severity of SMI symptoms. Furthermore, SMI symptom severity mediated the relationship between current trauma-related symptom severity, and illicit drug use providing indirect support for the self-medication hypothesis. The findings underscore the importance of assessing and providing for trauma-informed care to persons with SMI seeking services for co-occurring substance use disorders.