Impact of benzodiazepines and polysubstance status on repeat non-fatal drug overdoses

Research has shown that benzodiazepines and mental health disorders can increase the likelihood of repeat overdose, but researchers have not explored this association in Tennessee (TN). We examined benzodiazepines, polysubstance overdose status with/without benzodiazepines, and mental health comorbidities with repeat overdose using statewide data in TN. This study analyzed TN hospital discharge data on nonfatal overdoses for patients ages 18-64 from 2012 to 2016 for 21,066 patients with an initial inpatient visit and 36,244 patients with an initial outpatient visit. The study assessed each patient at one year after initial overdose to determine likelihood of repeat overdose. We used a Cox proportional hazards model to compute hazard ratios (HRs) and 95% confidence intervals (CIs) to determine the factors associated with repeat nonfatal overdose. Repeat overdose rates, by one year after index overdose, were 12.9% of the sample for inpatients and 13.9% of the sample for outpatients. The visit factors (overdose characteristics and comorbidities determined from the initial visit) that the study found to be independently associated with repeat overdoses among inpatients were polysubstance status (HR: 0.88, 95% CI 0.78-0.99), benzodiazepine/polysubstance interaction (HR: 1.29, 95% CI 1.02-1.64), and presence of any mental health disorder (HR: 1.28, 95% CI: 1.18-1.39). For outpatients, the benzodiazepine/polysubstance interaction (HR: 1.21, 95% CI 1.01-1.44) was significant without adjusting for demographic factors. We found evidence that benzodiazepine/polysubstance status and mental health disorders were associated with repeat overdose for inpatients, and that benzodiazepine/polysubstance status was associated with repeat overdose for outpatients. Findings support the need to include polysubstance status and mental health in overdose prevention efforts.