Most of the previous systematic reviews are methodologically problematic or limited in their analysis. The aim was to systematically review all RCTs of SSRIs versus placebo in OCD in adults using continuous and dichotomous efficacy data and adverse effects data.

All published RCTs were identified using Cochrane Collaboration's Depression, Anxiety and Neurosis Groups' Controlled Register, which includes all RCTs from other databases and other sources. Study selection and data extraction was carried out by two co-reviewers. The RCTs were quality assessed. Analysis included investigating publication bias, summary measures, sensitivity analysis, heterogeneity exploration and subgroup analysis.

Random effects model was used in view of clinical and some statistical heterogeneity. Overall pooled WMD for YBOCS (Yale Brown Obsessive Compulsive Scale) for all the studies of SSRIs was -3.21 (95% CI -3.84 to -2.57, number of RCTs 17, number of patients 3097). Pooled WMD for YBOCS of individual drugs were similar and not statistically different. Overall pooled RR for response across all the studies of all the 5 SSRIs was 1.84 (95% CI 1.56 to 2.17, number of RCTs 13, number of patients 2697). (Thus NNTs for patients with baseline risk of response rate of 10% would be 12 and of 20% would be 6). Pooled RR of individual drugs were similar and not statistically different.

SSRIs are effective in reducing symptoms in OCD in comparison to placebo. Potential benefits of SSRIs should be weighed against their adverse effects before prescribing these drugs.