title: Exploring the "active ingredients" of an online smoking intervention: a randomized factorial trial.
abstract: BACKGROUND
  Research needs to systematically identify which components increase online intervention effectiveness (i.e., active ingredients). This study explores the effects of 4 potentially important design features in an Internet-based, population-level smoking intervention.
  
  
  METHODS
  Smokers (n = 1,865) were recruited from a large health care organization, regardless of readiness to quit. Using a full factorial design, participants were randomized to 1 of the 2 levels of each experimental factor (message tone [prescriptive vs. motivational], navigation autonomy [dictated vs. not], e-mail reminders [yes vs. no], and receipt of personally tailored testimonials [yes vs. no]) and provided access to the online intervention. Primary outcomes were self-reported 7-day point-prevalent smoking abstinence and confirmed utilization of adjunct treatment (pharmacotherapy or phone counseling) available through the health plan at 1 year. Outcomes were also assessed at 2 and 6 months and were examined among all enrolled participants (intent-to-treat [ITT]) and all who viewed the intervention (modified ITT).
  
  
  RESULTS
  At 1 year, 13.7% were abstinent and 26.0% utilized adjunct treatment. None of the contrasting factor levels differentially influenced abstinence or treatment utilization at 12 months. In the modified ITT sample, smokers receiving testimonials were less likely to use adjunct treatment at 6 months (odds ratio = 0.54, 95% confidence interval = 0.30-0.98, p = .04).
  
  
  CONCLUSIONS
  None of the design features enhanced treatment outcome. The negative effect observed for testimonials is provocative, but it should be viewed with caution. This study offers a model for future research testing the "active ingredients" of online interventions.
authors.affiliation: Group Health Research Institute, Seattle, WA; mcclure.j@ghc.org.
authors.forename: Jennifer B
authors.initials: JB
authors.lastname: McClure
authors.affiliation: Group Health Research Institute, Seattle, WA;
authors.forename: Do
authors.initials: D
authors.lastname: Peterson
authors.affiliation: Center for Health Communications Research, University of Michigan, Ann Arbor, MI;
authors.forename: Holly
authors.initials: H
authors.lastname: Derry
authors.affiliation: Group Health Research Institute, Seattle, WA;
authors.forename: Karin
authors.initials: K
authors.lastname: Riggs
authors.affiliation: Group Health Research Institute, Seattle, WA;
authors.forename: Jackie
authors.initials: J
authors.lastname: Saint-Johnson
authors.affiliation: Department of Statistics, University of Michigan, Ann Arbor, MI.
authors.forename: Vijay
authors.initials: V
authors.lastname: Nair
authors.affiliation: Center for Health Communications Research, University of Michigan, Ann Arbor, MI;
authors.forename: Lawrence
authors.initials: L
authors.lastname: An
authors.affiliation: Group Health Research Institute, Seattle, WA;
authors.forename: Susan M
authors.initials: SM
authors.lastname: Shortreed
mesh_terms: D000328:Adult; D003376:Counseling; D034742:Electronic Mail; D005260:Female; D006801:Humans; D020407:Internet; D008297:Male; D008875:Middle Aged; D009042:Motivation; D012107:Research Design; D012907:Smoking / Q000628:therapy; D016540:Smoking Cessation / Q000379:methods*; D014029:Tobacco Use Disorder / Q000628:therapy; D016896:Treatment Outcome
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