A Random Forest Analysis of Risk Factors and Trends in Substance Use Treatment Among Those Who Use Cannabis and Alcohol Together Before and After the COVID-19 Pandemic

Background The harms of using combined cannabis and alcohol include injuries, social problems, and exacerbating existing conditions. No studies have compared substance use risk factors pre and post pandemic in a large national sample among those who use these substances together. The goal of our study was to determine the relationship between the pandemic and shifts in substance use among those who use cannabis and alcohol together.Methods This was a review of data collected by the National Survey of Drug Use and Health for the time frames (2015–2019 [pre-COVID], 2023 [post-COVID]). We analyzed data pertaining to whether respondents used cannabis during their last alcohol use. We analyzed demographic characteristics (e.g., age, gender, etc.), trends in treatment, and conducted random forest analyses followed by regression models for identifying significant predictors.Results Between 2015 and 2023 (including years 2020–2022), there were a total of 24,526 (5%) respondents who reported co-use and this increased during the study period (p < 0.001). Pre-COVID, 274 (2.1%) reported receipt of treatment and this increased to 141 (4.2%) (p < 0.0001). Pre-COVID, cannabis accessibility (aOR: 13.9, p < 0.0001) and amphetamine/methylphenidate products (aOR: 5.6, p < 0.001) were associated with co-use. Post COVID, cannabis accessibility (aOR: 10.6, p < 0.001) and psychotherapeutic misuse (aOR: 2.7, p < 0.001) were significant.Discussion Remnants of the COVID-19 pandemic, including the rise in mental health diagnoses, may have had a lasting influence on substance co-use. Efforts should be made to improve treatment rates in this population.