title: Internet-based cognitive behaviour therapy for symptoms of depression and anxiety: a meta-analysis.
abstract: BACKGROUND
  We studied to what extent internet-based cognitive behaviour therapy (CBT) programs for symptoms of depression and anxiety are effective.
  
  
  METHODS
  A meta-analysis of 12 randomized controlled trials.
  
  
  RESULTS
  The effects of internet-based CBT were compared to control conditions in 13 contrast groups with a total number of 2334 participants. A meta-analysis on treatment contrasts resulted in a moderate to large mean effect size [fixed effects analysis (FEA) d=0.40, mixed effects analysis (MEA) d=0.60] and significant heterogeneity. Therefore, two sets of post hoc subgroup analyses were carried out. Analyses on the type of symptoms revealed that interventions for symptoms of depression had a small mean effect size (FEA d=0.27, MEA d=0.32) and significant heterogeneity. Further analyses showed that one study could be regarded as an outlier. Analyses without this study showed a small mean effect size and moderate, non-significant heterogeneity. Interventions for anxiety had a large mean effect size (FEA and MEA d=0.96) and very low heterogeneity. When examining the second set of subgroups, based on therapist assistance, no significant heterogeneity was found. Interventions with therapist support (n=5) had a large mean effect size, while interventions without therapist support (n=6) had a small mean effect size (FEA d=0.24, MEA d=0.26).
  
  
  CONCLUSIONS
  In general, effect sizes of internet-based interventions for symptoms of anxiety were larger than effect sizes for depressive symptoms; however, this might be explained by differences in the amount of therapist support.
authors.affiliation: Department of Psychology and Health, Tilburg University, The Netherlands. v.r.m.spek@uvt.nl
authors.forename: Viola
authors.initials: V
authors.lastname: Spek
authors.forename: Pim
authors.initials: P
authors.lastname: Cuijpers
authors.forename: Ivan
authors.initials: I
authors.lastname: Nyklícek
authors.forename: Heleen
authors.initials: H
authors.lastname: Riper
authors.forename: Jules
authors.initials: J
authors.lastname: Keyzer
authors.forename: Victor
authors.initials: V
authors.lastname: Pop
mesh_terms: D001008:Anxiety Disorders / Q000175:diagnosis / Q000523:psychology / Q000628:therapy*; D015928:Cognitive Behavioral Therapy; D003866:Depressive Disorder / Q000175:diagnosis / Q000523:psychology / Q000628:therapy*; D006801:Humans; D020407:Internet; D010043:Outcome and Process Assessment, Health Care; D011369:Professional-Patient Relations; D016032:Randomized Controlled Trials as Topic; D012944:Social Support; D013813:Therapy, Computer-Assisted