Patterns of Expectancies Held Among Simultaneous Alcohol and Marijuana (SAM) Users
Authors: Berry Katherine , Falco Caitlin ,   The Stimulant Norms and Prevalence Study Team, Looby Alison 
Published: March 2022

Simultaneous alcohol and marijuana (SAM) use (i.e., using the two substances during the same period of time so that their effects overlap) is common among young adults. SAM use tends to be associated with greater negative consequences compared to the use of only one drug. Thus, understanding factors that may influence SAM use is necessary to inform interventions and limit harm. Substance use expectancies (i.e., beliefs regarding the anticipated positive and negative outcomes of engaging in a substance) are a strong predictor of alcohol and marijuana consumption and consequences, and may similarly explain SAM use. Positive expectancies (i.e., wanted outcomes, such as sociability) tend to predict the frequency of both alcohol and marijuana use, while negative expectancies (i.e., unwanted outcomes, such as cognitive and behavioral impairment) have been found to predict abstinence and a lower likelihood of use. Yet, alcohol and marijuana expectancies have not been sufficiently examined as related to SAM use. To address this gap in the literature, the present study examined 1012 college students (70.9% female, 51.8% white, Mage = 19.63) from seven US universities who reported past-month alcohol and marijuana use (77.2% of the sample reported SAM use). Participants completed expectancy measures for alcohol (7 factors) and marijuana (6 factors), and past-month SAM frequency. Collapsing individual expectancy factors into positive and negative expectancies by drug, a hierarchical multiple regression revealed that positive expectancies (F(2,1005) = 6.11, p = .002), but not negative expectancies (F(2,1003) = 0.04, p = .96), were significant predictors of SAM frequency above and beyond quantity and frequency of alcohol and marijuana use. Specifically, higher frequency of SAM use was associated with weaker positive alcohol (β = -0.08, p = .038) and stronger positive marijuana expectancies (β = 0.11, p = .003). A second hierarchical multiple regression examined which specific alcohol and marijuana expectancy factors accounted for these effects. After accounting for use variables, SAM frequency was associated with weaker social alcohol expectancies (β = -0.14, p = .007) and stronger sexual and social facilitation marijuana expectancies (β = 0.11, p = .009). Again, no negative expectancy factors were significant predictors of SAM frequency, nor did they incrementally contribute to model improvement. Contrary to the general expectancy literature, positive expectancies do not uniformly appear related to increased SAM use, as positive alcohol expectancies were inversely related to use. Positive marijuana expectancies, specifically social expectancies, on the other hand, were positively associated with SAM use. It is possible that individuals with strong social marijuana expectancies may add marijuana to their alcohol when they want to enhance socialization, perhaps, even more so when they believe that alcohol alone is not sufficient for obtaining optimal social functioning. Future research should further examine these relationships to understand whether these patterns of expectancies are causally related to SAM use or occur consequently. Moreover, given the positive associations between SAM use and positive marijuana expectancies, it may be efficacious to target positive marijuana expectancies when implementing intervention efforts that are designed to reduce SAM use.