Psychological Medicine

Review Article

Internet-based cognitive behaviour therapy for symptoms of depression and anxiety: a meta-analysis

a1 Department of Psychology and Health, Tilburg University, The Netherlands
a2 Diagnostic Centre Eindhoven, The Netherlands
a3 Department of Clinical Psychology, Vrije Universiteit Amsterdam, The Netherlands
a4 Trimbos-instituut, Netherlands Institute of Mental Health and Addiction, The Netherlands

Article author query
spek v   [PubMed][Google Scholar] 
cuijpers p   [PubMed][Google Scholar] 
nyklicek i   [PubMed][Google Scholar] 
riper h   [PubMed][Google Scholar] 
keyzer j   [PubMed][Google Scholar] 
pop v   [PubMed][Google Scholar] 


Background. We studied to what extent internet-based cognitive behaviour therapy (CBT) programs for symptoms of depression and anxiety are effective.

Method. 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.

(Published Online November 20 2006)

c1 Tilburg University, PO Box 90153, 5000 LE Tilburg, The Netherlands. (Email: