Co-use of alcohol and cannabis, where both substances are used simultaneously with overlapping effects, is increasingly prevalent among college students, with 73% of those who use both substances engaging in co-use behaviors. This simultaneous use is associated with more severe negative consequences than single-substance use, including heavier drinking, impaired driving, and increased risk of substance use disorders. While social norms theory demonstrates that individuals often overestimate peer substance use and adjust their behavior accordingly, research on social norms related to co-use remains limited. Although two-types of social norms—descriptive norms and injunctive norms—have been extensively associated with increased alcohol and cannabis use individually, their role in co-use behaviors represents a critical gap in the existing literature. To address these limitations, the current study aims to (1) explore variations in descriptive and injunctive norms across alcohol, cannabis, and co-use behaviors, (2) determine the relationships between these social norms and the frequency of co-use practices, and (3) evaluate the associations between co-use-related social norms and their negative consequences.
The study employed 209 college students aged 18-25 from Rhode Island universities who had used alcohol, cannabis, and engaged in co-use within the past year. Data were collected on demographic characteristics, descriptive norms (perceived percentage of same-gender, same-age peers engaging in monthly substance use behaviors), injunctive norms (perceived peer approval on a 7-point scale), typical substance use patterns, co-use frequency in the past 30 days, and co-use consequences using a 28-item questionnaire. The data were analyzed through paired t-tests to compare mean differences between substance-specific norms, regression models to examine relationships between norms and co-use frequency, and linear regression to assess associations between co-use norms and consequences, controlling for relevant demographic variables.
The study findings revealed that significant differences in perceived social norms across substance use behaviors. Regarding descriptive norms, participants perceived alcohol use as most prevalent among peers (M = 32.40%), followed by cannabis use (M = 26.38%), and co-use as least prevalent (M = 21.23%), with all differences being statistically significant. Similarly, for injunctive norms, participants believed their peers held the most accepting attitudes toward alcohol use (M = 6.05), followed by cannabis use (M = 5.66), and least accepting attitudes toward co-use (M = 5.14). Regression analyses examining predictors of co-use frequency showed that older age and higher co-use descriptive norms increased co-use frequency, while higher cannabis-only descriptive norms decreased it. For injunctive norms, older age and greater cannabis-only approval increased co-use frequency, whereas greater alcohol-only and co-use approval decreased it. Additionally, when examining co-use consequences, older age was associated with fewer consequences, while higher co-use descriptive norms and greater co-use frequency were associated with more negative consequences.
Takeaway: Perceived social norms—particularly co-use-specific descriptive norms—play a significant role in shaping the frequency and consequences of simultaneous alcohol and cannabis use among college students, highlighting the need for targeted interventions that address normative perceptions of co-use.