The legalization of marijuana across America may be increasing the prevalence of use in young adults. Some research has shown peer influence can be a determinant of drug use in young adults. The current study looks at random college roommates peer influence on marijuana use along with investigating the social nature of use.

Random roommates completed a web survey to gain information about demographics, pre-college and college health risk behaviors, and family background.  A total of 1,953 students were recruited. Other questions asked of the participants were about marijuana use before college and marijuana use in college. The participants were broken up into four groups; those who used before college but stopped using in college, those who used before college and in college, those who started using in college, and those who never used marijuana. To look at roommate influence the researchers examined the main effects of pre-college use and participants pre-college marijuana use and their college use. They then looked at the interaction effect of roommate’s pre-college use and participants pre-college use.

As was expected, participants who used marijuana prior to starting college were more likely to use once they were at college. Researchers found that peer influence depended significantly on predisposition. There was no effect for participants that had no pre-college use. They did find a significant peer effect for participants that had used marijuana before college. A roommate that was a pre-college marijuana user actually decreased the amount of college use. Having a roommate that never used marijuana or who used before college, but not in college proved to reduce marijuana use. These findings show that peer influence may differ based on past and present use of marijuana. It does also show that young adults who have stopped using marijuana may be helpful in intervention programs.

Take Away: With the legalization or marijuana rapidly changing, it is important to know how peer influence effects young adult marijuana use. The current study looks at random college roommates peer influence on marijuana use.  A total of 1,953 college students were recruited and asked about pre-college marijuana use along with college use. Peer influence was found to have no effect for those who had no pre-college use. Having a roommate that never used marijuana or who used before college, but not in college proved to reduce marijuana use. These findings show that peer influence may differ based on history and present use of marijuana. It does also show that young adults who have stopped using marijuana may be helpful in intervention programs.

Li, Y., & Guo, G. (2020). Heterogeneous peer effects on marijuana use: Evidence from a natural experiment. Social Science & Medicine, 252, 112907. doi: 10.1016/j.socscimed.2020.112907