Alcohol and Marijuana use in Undergraduate Males: Between- and Within-Person Associations with Interpersonal Conflict.

Background: Among college students, interpersonal conflict with others is a common, yet stressful negative interpersonal experience. Research suggests that drinking episodes may contribute to the occurrence of conflict. Marijuana use, independently or in conjunction with alcohol, may also influence the likelihood of subsequent conflict.

Objectives: We considered the temporal effects of independent and simultaneous alcohol and marijuana use episodes on the occurrence of interpersonal conflict. Use of multilevel modeling allowed us to distinguish the within-person effects of substance use from between-person differences in frequency of use.

Methods: Within a sample of 427 college freshman males over 56 days of daily reports, we examined the independent and interactive effects of episodes of alcohol and marijuana on the odds of conflict within the next 1-, 2-, 3-, and 4 hours.

Results: Multilevel modeling analyses showed that drinking episodes increased the likelihood of conflict occurring within the next 1, 2, 3, and 4 hours. Marijuana had weaker positive effects, significant only within the 2 hour window. There were no alcohol by marijuana interaction effects in any analysis.

Conclusions/Importance: Both marijuana and alcohol independently increased the likelihood of interpersonal conflict; however, the marijuana effect appeared less robust. As marijuana use becomes more normative and accessible for college students, it is important to understand the extent to which marijuana use results in negative consequences and the contexts under which these effects unfold.