To investigate the effectiveness of a freely available computerised cognitive behavioural therapy programme (MoodGYM) for depression (primary outcome), anxiety and general psychological distress in adults.

We searched PsycINFO, CINAHL Plus, MEDLINE, EMBASE, Social Science Citation Index and references from identified papers. To assess MoodGYM’s effectiveness, we conducted random effects meta-analysis of identified randomised controlled trials.

Comparisons from 11 studies demonstrated MoodGYM’s effectiveness for depression symptoms at post-intervention, with a small effect size (g = 0.36, 95% confidence interval: 0.17–0.56; I² = 78%). Removing the lowest quality studies (k = 3) had minimal impact; however, adjusting for publication bias reduced the effect size to a non-significant level (g = 0.17, 95% confidence interval: –0.01 to 0.38). Comparisons from six studies demonstrated MoodGYM’s effectiveness for anxiety symptoms at post-intervention, with a medium effect size (g = 0.57, 95% confidence interval: 0.20–0.94; I² = 85%). Although comparisons from six studies did not yield significance for MoodGYM’s effectiveness for general psychological distress symptoms, the small effect size approached significance (g = 0.34, 95% confidence interval: –0.04 to 0.68; I² = 79%). Both the type of setting (clinical vs non-clinical) and MoodGYM-developer authorship in randomised controlled trials had no meaningful influence on results; however, the results were confounded by the type of control deployed, level of clinician guidance, international region of trial and adherence to MoodGYM.

The confounding influence of several variables, and presence of publication bias, means that the results of this meta-analysis should be interpreted with caution. Tentative support is provided for MoodGYM’s effectiveness for symptoms of depression and general psychological distress. The programme’s medium effect on anxiety symptoms demonstrates its utility for people with this difficulty. MoodGYM benefits from its free accessibility over the Internet, but adherence rates can be problematic and at the extreme can fall below 10%. We conclude that MoodGYM is best placed as a population-level intervention that is likely to benefit a sizeable minority of its users.