title: Licit and Illicit Substance Use by Adolescent E-Cigarette Users Compared with Conventional Cigarette Smokers, Dual Users, and Nonusers.
abstract: OBJECTIVE
  Compare the lifetime prevalence of eight forms of substance use (alcohol, drunkenness, oral tobacco, snuff, sleeping pills/tranquilizers, sniffed glue, marijuana, and amphetamine) among adolescent e-cigarette (EC) users, conventional cigarette (CC) smokers, dual users, and nonusers.
  
  
  METHODS
  We analyzed population-level school-survey data collected from 10th-grade students (aged 15-16 years) in February 2015 in Iceland (N = 3,477; response rate, 84.4%).
  
  
  RESULTS
  Smoking rates were similar for both sexes. Around 17% had used ECs and almost 8% had used ECs and not combustible tobacco, 5%-6% had smoked CCs but not ECs, around 9% were dual users. EC-only users were significantly more likely than nonusers to have used the eight substances investigated in the study but were less likely to have used these substances than CC smokers and dual users.
  
  
  CONCLUSIONS
  The four groups assessed in this study appear to form a sequential risk gradient to the use of other substances.
authors.affiliation: Department of Social and Behavioral Sciences, School of Public Health, West Virginia University, Morgantown, West Virginia; Icelandic Center for Social Research and Analysis, Reykjavik University, Reykjavik, Iceland. Electronic address: alkristjansson@hsc.wvu.edu.
authors.forename: Alfgeir L
authors.initials: AL
authors.lastname: Kristjansson
authors.affiliation: Department of Social and Behavioral Sciences, School of Public Health, West Virginia University, Morgantown, West Virginia.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Mann
authors.affiliation: Icelandic Center for Social Research and Analysis, Reykjavik University, Reykjavik, Iceland; Department of Psychology, Reykjavik University, Reykjavik, Iceland; Department of Health and Behavior Studies, Teachers College, Columbia University, New York, New York.
authors.forename: Inga Dora
authors.initials: ID
authors.lastname: Sigfusdottir
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior; D000428:Alcohol Drinking / Q000453:epidemiology*; D066300:Electronic Nicotine Delivery Systems / Q000706:statistics & numerical data*; D006801:Humans; D007055:Iceland / Q000453:epidemiology; D013287:Illicit Drugs; D015995:Prevalence; D019966:Substance-Related Disorders / Q000453:epidemiology*; D064424:Tobacco Use / Q000453:epidemiology*; D014481:United States / Q000453:epidemiology
chemical_list: D013287:Illicit Drugs
keywords: Electronic cigarettes; Iceland; Primary prevention; Smokeless tobacco; Vapors