title: Internet and computer based interventions for cannabis use: a meta-analysis.
abstract: BACKGROUND
  Worldwide, cannabis is the most prevalently used illegal drug and creates demand for prevention and treatment services that cannot be fulfilled using conventional approaches. Computer and Internet-based interventions may have the potential to meet this need. Therefore, we systematically reviewed the literature and conducted a meta-analysis on the effectiveness of this approach in reducing the frequency of cannabis use.
  
  
  METHODS
  We systematically searched online databases (Medline, PubMed, PsychINFO, Embase) for eligible studies and conducted a meta-analysis. Studies had to use a randomized design, be delivered either via the Internet or computer and report separate outcomes for cannabis use. The principal outcome measure was the frequency of cannabis use.
  
  
  RESULTS
  Data were extracted from 10 studies and the meta-analysis involved 10 comparisons with 4,125 participants. The overall effect size was small but significant, g=0.16 (95% confidence interval (CI) 0.09-0.22, P<0.001) at post-treatment. Subgroup analyses did not reveal significant subgroup differences for key factors including type of analysis (intention-to-treat, completers only), type of control (active, waitlist), age group (11-16, 17+ years), gender composition (female only, mixed), type of intervention (prevention, 'treatment'), guided versus unguided programs, mode of delivery (Internet, computer), individual versus family dyad and venue (home, research setting). Also, no significant moderation effects were found for number of sessions and time to follow-up. Finally, there was no evidence of publication bias.
  
  
  CONCLUSIONS
  Internet and computer interventions appear to be effective in reducing cannabis use in the short-term albeit based on data from few studies and across diverse samples.
authors.affiliation: Centre for Mental Health Research, Australian National University, Canberra, ACT, Australia; National Drug Research Institute, Curtin University, Perth, WA, Australia. Electronic address: Robert.Tait@curtin.edu.au.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Tait
authors.forename: Renske
authors.initials: R
authors.lastname: Spijkerman
authors.forename: Heleen
authors.initials: H
authors.lastname: Riper
mesh_terms: D000328:Adult; D054626:Consumer Health Information; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D020407:Internet; D008297:Male; D002189:Marijuana Abuse / Q000534:rehabilitation*; D008838:Microcomputers; D017594:Publication Bias; D012044:Regression Analysis
keywords: Cannabis; Computer; Internet; Intervention; Meta-analysis; Prevention; Substance use; Systematic review