The Role of Drugs in Alcohol Poisoning and Blackout Events: A Latent Class Analysis of a Residential Treatment Sample

BACKGROUND: Alcohol can lead to fatal and nonfatal overdose (OD) through its neurobiological inhibitory effects when used alone or with other drugs. Little research has examined alcohol OD characteristics in the context of concomitant drug use. METHODS: This study utilized alcohol OD data (defined as alcohol poisoning, passing out, or blacking out) collected in a large residential addiction treatment facility (N = 660). Latent class analysis identified classes of alcohol OD events based on concomitant drug use at the time of OD. We evaluated correlates of alcohol OD classes, including depression, emergency medical services, and hospitalization, using latent class regression. RESULTS: Only 20% of alcohol ODs involved alcohol alone. Marijuana was the most commonly used drug during the most recent alcohol OD (43.2%), followed by sedatives (27.9%), cocaine or crack (25.9%), prescription opioids (26.1%), and heroin (20%). The final latent class model included 3 classes: no/low drug involvement (61%), moderate drug involvement (33%), and high drug involvement (6%). Relative to the no/low drug involvement class, participants admitted to the hospital were 6.4‐fold more likely to be in the high drug involvement class (95% CI: 2.4 to 16.6) and 2.9‐fold more likely to be in the moderate drug involvement class (95% CI: 1.2 to 7.2). Participants receiving emergency medical services were more likely to be in the high drug involvement class (aOR: 2.2, 95% CI: 2.2, 1.1 to 4.5) and less likely to be in the moderate drug involvement class (aOR 0.39, 95% CI: 0.2 to 0.96). CONCLUSIONS: Combining drug classes with alcohol prior to OD was common and associated with a higher likelihood of hospitalization. Overdose prevention efforts should address acute risks of alcohol ingestion with other drugs.