title: Assessing the overlap between tobacco and marijuana: Trends in patterns of co-use of tobacco and marijuana in adults from 2003-2012.
abstract: BACKGROUND
  As marijuana legalization and acceptability increase in the U.S., it is important to understand the potential impact on tobacco use. Accordingly, we assessed prevalence, correlates, and ten-year trends in co-use of marijuana and tobacco among U.S. adults.
  
  
  METHODS
  Data came from 378,459 adults participating in the 2003-2012 National Survey on Drug Use and Health, an annual, cross-sectional, household survey. Data from 2011-2012 were used to compute the most recent prevalence of past 30-day marijuana and tobacco use (co-use). Data from 2003-2012 were used to compute demographic correlates of co-use, overall trends in co-use, and trends by age, race, and sex. We also assessed trends in tobacco use among marijuana users and marijuana use among tobacco users.
  
  
  RESULTS
  From 2011 to 2012, 5.2% of participants were past month co-marijuana and tobacco users, 24.0% were tobacco-only users, and 2.3% were marijuana-only users. From 2003 to 2012, prevalence of co-use increased overall (p<.0001), and among males and females (p<.001, p<.05), those ages 26-34 (p<.001) and 50+years (p<.0001), and Whites (p<.01), Blacks (p<.05), and Hispanics (p<.01); there were no changes among adults 18-25 years. Tobacco use among marijuana users decreased between 2003 and 2012 (from 74.3% to 69.6%, p<.0001), while marijuana use increased among tobacco users (from 14.2% to 17.8, p<.0001).
  
  
  CONCLUSIONS
  Co-use of tobacco and marijuana increased from 2003-2012, with marijuana use increasing among past-month tobacco users and tobacco use declining among past-month marijuana users. Improved surveillance of co-use is needed as marijuana legalization policies expand and become more integrated in communities.
authors.affiliation: Department of Behavioral Sciences and Health Education, Emory University, 1518 Clifton Road NE, Atlanta, GA 30322, United States. Electronic address: gillian.schauer@emory.edu.
authors.forename: Gillian L
authors.initials: GL
authors.lastname: Schauer
authors.affiliation: Department of Behavioral Sciences and Health Education, Emory University, 1518 Clifton Road NE, Atlanta, GA 30322, United States.
authors.forename: Carla J
authors.initials: CJ
authors.lastname: Berg
authors.affiliation: Department of Behavioral Sciences and Health Education, Emory University, 1518 Clifton Road NE, Atlanta, GA 30322, United States.
authors.forename: Michelle C
authors.initials: MC
authors.lastname: Kegler
authors.affiliation: Alcohol & Drug Abuse Institute, University of Washington, 1107 NE 45th Street, Seattle, WA 98105, United States.
authors.forename: Dennis M
authors.initials: DM
authors.lastname: Donovan
authors.affiliation: Department of Behavioral Sciences and Health Education, Emory University, 1518 Clifton Road NE, Atlanta, GA 30322, United States.
authors.forename: Michael
authors.initials: M
authors.lastname: Windle
mesh_terms: D000293:Adolescent; D000328:Adult; D001741:Black or African American / Q000706:statistics & numerical data; D017677:Age Distribution; D000428:Alcohol Drinking / Q000453:epidemiology* / Q000208:ethnology; D015897:Comorbidity / Q000639:trends; D003430:Cross-Sectional Studies; D004522:Educational Status; D004651:Employment; D005260:Female; D006304:Health Status; D006630:Hispanic or Latino / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D008385:Marijuana Smoking / Q000453:epidemiology* / Q000208:ethnology; D008875:Middle Aged; D017678:Sex Distribution; D012907:Smoking / Q000453:epidemiology* / Q000208:ethnology; D014481:United States / Q000453:epidemiology; D044465:White People / Q000706:statistics & numerical data; D055815:Young Adult
keywords: Cannabis; Epidemiology; Marijuana; Smoking; Surveillance; Tobacco