Marijuana use trajectories during the post-college transition: Health outcomes in young adulthood (2012)

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