title: Prevalence and co-use of marijuana among young adult cigarette smokers: An anonymous online national survey.
abstract: BACKGROUND
  There is elevated prevalence of marijuana use among young adults who use tobacco, but little is known about the extent of co-use generated from surveys conducted online. The purpose of the present study was to examine past-month marijuana use and the co-use of marijuana and tobacco in a convenience sample of young adult smokers with national US coverage.
  
  
  METHODS
  Young adults age 18 to 25 who had smoked at least one cigarette in the past 30 days were recruited online between 4/1/09 and 12/31/10 to participate in an online survey on tobacco use. We examined past 30 day marijuana use, frequency of marijuana use, and proportion of days co-using tobacco and marijuana by demographic characteristics and daily smoking status.
  
  
  RESULTS
  Of 3512 eligible and valid survey responses, 1808 (51.5%) smokers completed the survey. More than half (53%, n = 960) of the sample reported past-month marijuana use and reported a median use of 18 out of the past 30 days (interquartile range [IR] = 4, 30). Co-use of tobacco and marijuana occurred on nearly half (median = 45.5%; IR = 13.1, 90.3) of the days on which either substance was used and was more frequent among Caucasians, respondents living in the Northeast or in rural areas, in nonstudents versus students, and in daily versus nondaily smokers. Residence in a state with legalized medical marijuana was unrelated to co-use or even the prevalence of marijuana use in this sample. Age and household income also were unrelated to co-use of tobacco and marijuana.
  
  
  CONCLUSIONS
  These results indicate a higher prevalence of marijuana use and co-use of tobacco in young adult smokers than is reported in nationally representative surveys. Cessation treatments for young adult smokers should consider broadening intervention targets to include marijuana.
authors.affiliation: Department of Psychiatry, University of California at San Francisco, 401 Parnassus Avenue,, Box TRC 0984, San Francisco, CA 94143, USA. danielle.ramo@ucsf.edu
authors.forename: Danielle E
authors.initials: DE
authors.lastname: Ramo
authors.forename: Judith J
authors.initials: JJ
authors.lastname: Prochaska
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D005260:Female; D006306:Health Surveys; D006801:Humans; D020407:Internet; D008297:Male; D008385:Marijuana Smoking / Q000453:epidemiology; D015995:Prevalence; D012737:Sex Factors; D012907:Smoking / Q000453:epidemiology*; D012959:Socioeconomic Factors; D055815:Young Adult