Abstract
BACKGROUND: Although several risk factors for suicidal ideation (SI) have been identified in the research literature, there is a pressing need for studies evaluating markers of risk differentiating ideators from people who have attempted. According to the interpersonal theory of suicide, habituation to painful or provocative experiences increases one's acquired capability for suicide, a necessary component for the transition from SI to attempts. This theory further posits that the acquired capability for suicide should be unrelated to risk for SI. This study tested this theory by examining injection drug use, relative to less painful means of drug use, in relation to SI, suicide plans, and suicide attempts. METHODS: Data were drawn from the National Survey on Drug Use and Health (NSDUH), a nationally representative survey conducted annually. Participants included 10,203 adults with a history of injectable drug use and major depression. RESULTS: Injection drug use was positively associated with suicide attempts (Odds Ratio [OR] = 1.66, 95% confidence interval [CI] = 1.18-2.34), but not SI or suicide plans in the full sample. Injection drug use was also associated with suicide attempts (OR = 1.64, 95% CI = 1.14-2.35), but not plans, among ideators. Lastly, injection drug use was associated with the suicide attempts among suicide planners (OR = 1.76, 95% CI = 1.01-3.06). All analyses included sex, age, race/ethnicity, family income, substance use disorder symptom severity for injectable drugs, and depressive symptom severity as covariates. CONCLUSIONS: Consistent with the interpersonal theory of suicide, injection drug use was associated with specific risk for suicide attempts but not SI or suicide plans.