title: Alcohol and cannabis use among college students: Substitutes or complements?
abstract: OBJECTIVE
  Economists debate whether changes in availability of alcohol or cannabis are positively or negatively related to changes in use of the other substance. Implicit in these arguments are two competing, individual-level hypotheses-that people use alcohol and cannabis either as complements or substitutes for one another. This is the first study to test these hypotheses using micro-longitudinal data on individuals' alcohol and cannabis use on a given evening.
  
  
  METHODS
  United States college students who use alcohol and cannabis (n=876) were selected from a larger sample who participated in a 30-day online daily diary study. At baseline, students reported their proclivity to use alcohol/drugs to cope with stress. Each day students reported their level of alcohol use from the prior evening as well as whether they had used cannabis.
  
  
  RESULTS
  Evening levels of alcohol use and mean levels of alcohol use positively predicted the likelihood of evening cannabis use, results indicative of complementary use. This relation, however, was moderated by coping style, such that students who were more likely to use alcohol/drugs to cope were less likely to use cannabis as their evening or mean alcohol use levels increased, results indicative of substitution.
  
  
  CONCLUSIONS
  Substance-using college students showed evidence for complementary alcohol and cannabis use at both the within- and between-person levels. Students with a proclivity toward using alcohol/drugs to cope, however, showed evidence of substitution. These findings suggest that studies based on economic theories of substance use should take into account individual differences in substance use motives.
authors.affiliation: Department of Psychiatry, 263 Farmington Avenue, Farmington, CT 06030-1410, USA. Electronic address: rossohara.psych@gmail.com.
authors.forename: Ross E
authors.initials: RE
authors.lastname: O'Hara
authors.affiliation: Department of Psychology, Fairleigh Dickinson University, Metropolitan Campus, 1000 River Road, Teaneck, NJ 07666-1914, USA. Electronic address: armeli@fdu.edu.
authors.forename: Stephen
authors.initials: S
authors.lastname: Armeli
authors.affiliation: Department of Community Medicine & Health Care, 263 Farmington Avenue, Farmington, CT 06030-1410, USA. Electronic address: tennen@nso1.uchc.edu.
authors.forename: Howard
authors.initials: H
authors.lastname: Tennen
mesh_terms: D000223:Adaptation, Psychological; D000293:Adolescent; D000428:Alcohol Drinking / Q000453:epidemiology* / Q000523:psychology; D000067292:Alcohol Drinking in College / Q000523:psychology*; D005260:Female; D006801:Humans; D007206:Individuality; D008137:Longitudinal Studies; D008297:Male; D008385:Marijuana Smoking / Q000453:epidemiology* / Q000523:psychology; D009042:Motivation; D013334:Students / Q000523:psychology / Q000706:statistics & numerical data*; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology; D014495:Universities; D055815:Young Adult
keywords: Alcohol; Cannabis; College student; Complement; Coping; Substitution