Marijuana use trajectories during the post-college transition: health outcomes in young adulthood

Despite the relatively high prevalence of marijuana use among college students, little information exists regarding health outcomes associated with different use patterns or trajectories.

Seven annual personal interviews (years 1-7) were administered to 1253 individuals, beginning in their first year in college. Growth mixture modeling was used to identify trajectories of marijuana, alcohol, and tobacco use frequency during years 1-6. Logistic regression was used to evaluate the relationship between marijuana use trajectories and several year 7 health outcomes, holding constant year 1 health, demographics, and alcohol and tobacco use trajectories.

Six marijuana use trajectories were identified: non-use (71.5% (wt) of students), low-stable (10.0% (wt)), late-increase (4.7% (wt)), early-decline (4.3% (wt)), college-peak (5.4% (wt)), and chronic (4.2% (wt)). The six marijuana trajectory groups were not significantly different on year 1 health-related variables, but differed on all ten year 7 health outcomes tested, including functional impairment due to injury, illness, or emotional problems; general health rating; psychiatric symptoms; health-related quality of life; and service utilization for physical and mental health problems. Non-users fared significantly better than most of the marijuana-using trajectory groups on every outcome tested. Chronic and late-increase users had the worst health outcomes.

Marijuana use patterns change considerably during college and the post-college period. Marijuana-using students appear to be at risk for adverse health outcomes, especially if they increase or sustain a frequent pattern of use.