title: Marijuana use trajectories and academic outcomes among college students.
abstract: BACKGROUND
  Marijuana is the most commonly used illicit drug by college students. Prior studies have established an association between marijuana use and poor academic performance in college, but research on the frequency of marijuana use over the entire college career is limited. The study objective was to examine the association of marijuana use trajectories on academic outcomes, including senior year enrollment, plans to graduate on time, and GPA.
  
  
  METHODS
  Data were collected from a cohort of 3146 students from 11 colleges in North Carolina and Virginia at six time points across the college career. Group-based trajectory models were used to characterize longitudinal marijuana use patterns during college. Associations between marijuana trajectory groups and academic outcomes were modeled using random-effects linear and logistic regressions.
  
  
  RESULTS
  Five marijuana trajectory groups were identified: non-users (69.0%), infrequent users (16.6%), decreasing users (4.7%), increasing users (5.8%), and frequent users (3.9%). Decreasing users and frequent users were more likely to drop out of college and plan to delay graduation when compared to non-users. All marijuana user groups reported lower GPAs, on average, than non-users.
  
  
  CONCLUSIONS
  These results identify marijuana use patterns that put students at risk for poor academic performance in college. Students who use marijuana frequently at the beginning of the college career are especially at risk for lower academic achievement than non-users, suggesting that early intervention is critical.
authors.affiliation: Department of Biostatistical Sciences, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, United States. Electronic address: CSuerken@wakehealth.edu.
authors.forename: Cynthia K
authors.initials: CK
authors.lastname: Suerken
authors.affiliation: Department of Biostatistical Sciences, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, United States; Department of Social Sciences and Health Policy, Wake Forest School of Medicine, Medical Center Blvd, Winston-Salem, NC 27157, United States.
authors.forename: Beth A
authors.initials: BA
authors.lastname: Reboussin
authors.affiliation: Department of Social Sciences and Health Policy, Wake Forest School of Medicine, Medical Center Blvd, Winston-Salem, NC 27157, United States.
authors.forename: Kathleen L
authors.initials: KL
authors.lastname: Egan
authors.affiliation: Department of Social Sciences and Health Policy, Wake Forest School of Medicine, Medical Center Blvd, Winston-Salem, NC 27157, United States.
authors.forename: Erin L
authors.initials: EL
authors.lastname: Sutfin
authors.affiliation: Department of Social Sciences and Health Policy, Wake Forest School of Medicine, Medical Center Blvd, Winston-Salem, NC 27157, United States.
authors.forename: Kimberly G
authors.initials: KG
authors.lastname: Wagoner
authors.affiliation: Department of Family and Community Medicine, Wake Forest School of Medicine, Medical Center Blvd, Winston-Salem, NC 27157, United States.
authors.forename: John
authors.initials: J
authors.lastname: Spangler
authors.affiliation: Department of Social Sciences and Health Policy, Wake Forest School of Medicine, Medical Center Blvd, Winston-Salem, NC 27157, United States.
authors.forename: Mark
authors.initials: M
authors.lastname: Wolfson
mesh_terms: D002188:Cannabis / Q000009:adverse effects*; D004522:Educational Status; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008385:Marijuana Smoking / Q000453:epidemiology* / Q000523:psychology; D009657:North Carolina / Q000453:epidemiology; D013334:Students / Q000523:psychology / Q000706:statistics & numerical data*; D014495:Universities; D014768:Virginia / Q000453:epidemiology
keywords: Academic performance; College students; Early intervention; Longitudinal study; Marijuana; Trajectory modeling