title: Longitudinal influence of alcohol and marijuana use on academic performance in college students.
abstract: BACKGROUND
  Alcohol and marijuana are the two most abused substances in US colleges. However, research on the combined influence (cross sectional or longitudinal) of these substances on academic performance is currently scant.
  
  
  METHODS
  Data were derived from the longitudinal 2-year Brain and Alcohol Research in College Students (BARCS) study including 1142 freshman students who completed monthly marijuana use and alcohol consumption surveys. Subjects were classified into data-driven groups based on their alcohol and marijuana consumption. A linear mixed-model (LMM) was employed using this grouping factor to predict grade point average (GPA), adjusted for a variety of socio-demographic and clinical factors.
  
  
  RESULTS
  Three data-driven clusters emerged: 1) No/low users of both, 2) medium-high alcohol/no-low marijuana, and 3) medium-high users of both substances. Individual cluster derivations between consecutive semesters remained stable. No significant interaction between clusters and semester (time) was noted. Post-hoc analysis suggest that at the outset, compared to sober peers, students using moderate to high levels of alcohol and low marijuana demonstrate lower GPAs, but this difference becomes non-significant over time. In contrast, students consuming both substances at moderate-to-high levels score significantly lower at both the outset and across the 2-year investigation period. Our follow-up analysis also indicate that when students curtailed their substance use over time they had significantly higher academic GPA compared to those who remained stable in their substance use patterns over the two year period.
  
  
  CONCLUSIONS
  Overall, our study validates and extends the current literature by providing important implications of concurrent alcohol and marijuana use on academic achievement in college.
authors.affiliation: Olin Neuropsychiatry Research Center, Hartford HealthCare Corporation, Hartford, Connecticut, United States of America.
authors.forename: Shashwath A
authors.initials: SA
authors.lastname: Meda
authors.affiliation: Department of Biostatistics, Yale School of Public Health, New Haven, Connecticut, United States of America.|Department of Psychiatry, Yale University, New Haven, Connecticut, United States of America.
authors.forename: Ralitza V
authors.initials: RV
authors.lastname: Gueorguieva
authors.affiliation: Department of Psychiatry, Yale University, New Haven, Connecticut, United States of America.
authors.forename: Brian
authors.initials: B
authors.lastname: Pittman
authors.affiliation: Olin Neuropsychiatry Research Center, Hartford HealthCare Corporation, Hartford, Connecticut, United States of America.
authors.forename: Rivkah R
authors.initials: RR
authors.lastname: Rosen
authors.affiliation: Olin Neuropsychiatry Research Center, Hartford HealthCare Corporation, Hartford, Connecticut, United States of America.
authors.forename: Farah
authors.initials: F
authors.lastname: Aslanzadeh
authors.affiliation: Department of Psychology and Neurosciences, Trinity College, Hartford, Connecticut, United States of America.
authors.forename: Howard
authors.initials: H
authors.lastname: Tennen
authors.affiliation: Olin Neuropsychiatry Research Center, Hartford HealthCare Corporation, Hartford, Connecticut, United States of America.
authors.forename: Samantha
authors.initials: S
authors.lastname: Leen
authors.affiliation: Department of Psychiatry, Yale University, New Haven, Connecticut, United States of America.
authors.forename: Keith
authors.initials: K
authors.lastname: Hawkins
authors.affiliation: Department of Community Medicine, University of Connecticut School of Medicine, Farmington, Connecticut, United States of America.
authors.forename: Sarah
authors.initials: S
authors.lastname: Raskin
authors.affiliation: Department of Psychology, Central Connecticut State University, New Britain, Connecticut, United States of America.
authors.forename: Rebecca M
authors.initials: RM
authors.lastname: Wood
authors.affiliation: Department of Psychology, Central Connecticut State University, New Britain, Connecticut, United States of America.
authors.forename: Carol S
authors.initials: CS
authors.lastname: Austad
authors.affiliation: Olin Neuropsychiatry Research Center, Hartford HealthCare Corporation, Hartford, Connecticut, United States of America.|Department of Psychiatry, Yale University, New Haven, Connecticut, United States of America.
authors.forename: Alecia
authors.initials: A
authors.lastname: Dager
authors.affiliation: Department of Psychology, Central Connecticut State University, New Britain, Connecticut, United States of America.
authors.forename: Carolyn
authors.initials: C
authors.lastname: Fallahi
authors.affiliation: Olin Neuropsychiatry Research Center, Hartford HealthCare Corporation, Hartford, Connecticut, United States of America.|Department of Psychiatry, Yale University, New Haven, Connecticut, United States of America.|Department of Neurobiology, Yale University, New Haven, Connecticut, United States of America.
authors.forename: Godfrey D
authors.initials: GD
authors.lastname: Pearlson
mesh_terms: D000124:Achievement; D000293:Adolescent; D000428:Alcohol Drinking; D001007:Anxiety / Q000473:pathology; D016000:Cluster Analysis; D003863:Depression / Q000473:pathology; D005260:Female; D006801:Humans; D016014:Linear Models; D008137:Longitudinal Studies; D008297:Male; D008385:Marijuana Smoking; D012923:Social Class; D013334:Students / Q000706:statistics & numerical data*; D014495:Universities; D055815:Young Adult