title: Risk factors for exclusive e-cigarette use and dual e-cigarette use and tobacco use in adolescents.
abstract: OBJECTIVE
  To describe electronic cigarette (e-cigarette) use and cigarette use among adolescents and determine whether established risk factors for smoking discriminate user categories.
  
  
  METHODS
  School-based survey of 1941 high school students (mean age 14.6 years) in Hawaii; data collected in 2013. The survey assessed e-cigarette use and cigarette use, alcohol and marijuana use, and psychosocial risk and protective variables (eg, parental support, academic involvement, smoking expectancies, peer smoking, sensation seeking). Analysis of variance and multinomial regression examined variation in risk and protective variables across the following categories of ever-use: e-cigarette only, cigarette only, dual use (use of both products), and nonuser (never used either product).
  
  
  RESULTS
  Prevalence for the categories was 17% (e-cigarettes only), 12% (dual use), 3% (cigarettes only), and 68% (nonusers). Dual users and cigarette-only users were highest on risk status (elevated on risk factors and lower on protective factors) compared with other groups. E-cigarette only users were higher on risk status than nonusers but lower than dual users. E-cigarette only users and dual users more often perceived e-cigarettes as healthier than cigarettes compared with nonusers.
  
  
  CONCLUSIONS
  This study reports a US adolescent sample with one of the largest prevalence rates of e-cigarette only use in the existing literature. Dual use also had a substantial prevalence. The fact that e-cigarette only users were intermediate in risk status between nonusers and dual users raises the possibility that e-cigarettes are recruiting medium-risk adolescents, who otherwise would be less susceptible to tobacco product use.
authors.affiliation: University of Hawaii Cancer Center, Honolulu, Hawaii; Twills@cc.hawaii.edu.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Wills
authors.affiliation: University of Hawaii Cancer Center, Honolulu, Hawaii;
authors.forename: Rebecca
authors.initials: R
authors.lastname: Knight
authors.affiliation: University of Hawaii at Manoa, Honolulu, Hawaii; and.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Williams
authors.affiliation: University of Hawaii Cancer Center, Honolulu, Hawaii;
authors.forename: Ian
authors.initials: I
authors.lastname: Pagano
authors.affiliation: Norris Cotton Cancer Center, Lebanon, New Hampshire.
authors.forename: James D
authors.initials: JD
authors.lastname: Sargent
mesh_terms: D000293:Adolescent; D003430:Cross-Sectional Studies; D066300:Electronic Nicotine Delivery Systems / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D015995:Prevalence; D012307:Risk Factors; D012907:Smoking / Q000453:epidemiology*; D064424:Tobacco Use / Q000453:epidemiology*
keywords: adolescence; cigarettes; electronic cigarettes; prevalence; protective factors; risk factors