Association between substance‐induced psychosis and suicide attempt: A Danish nation‐wide register‐based study

Abstract

Background and aimsSubstance‐induced psychosis has previously been linked to an excess risk of suicide; however, the association between substance‐induced psychosis and suicide attempt has hitherto not been investigated. We investigated whether substance‐induced psychosis was associated with a higher risk of subsequent suicide attempt.DesignNation‐wide prospective register‐based cohort study.SettingDenmark.ParticipantsAll people living in Denmark aged 13 years or more during 1995 to 2017.MeasurementsSubstance‐induced psychosis and suicide attempts were identified through hospital records as ICD‐10 codes.FindingsA total of 8900 (78.8% males) individuals were diagnosed with a substance‐induced psychosis, and 740 of these had a suicide attempt during follow‐up. People with a substance‐induced psychosis had a higher risk of a subsequent suicide attempt [hazard ratio (HR) = 13.4, 95% confidence interval (CI) = 12.4–14.4] when compared with the general population. The highest hazard ratios were found for psychosis induced by opioids (HR = 26.4, 95% CI = 18.2–38.2); alcohol (HR = 17.7, 95% CI = 15.2–20.6); sedatives (HR = 17.2, 95% CI = 8.9–33.0); and cocaine (HR = 15.6, 95% CI = 10.7–22.8), while cannabis‐induced psychosis was linked to an HR of 8.9 (95% CI = 7.7–10.3). Approximately 15% of patients with substance‐induced psychosis had had a suicide attempt within 20 years of their substance‐induced psychosis diagnosis.ConclusionsIn Denmark, substance‐induced psychosis appears to be strongly associated with subsequent suicide attempt, underscoring the importance of attention and better follow‐up for this patient group.