Cognitive Behavioural Therapy with Exposure and Response Prevention in the treatment of Obsessive-Compulsive Disorder: A systematic review and meta-analysis of randomised controlled trials

Background: Cognitive behavioural therapy (CBT), incorporating exposure and response prevention (ERP) is widely recognised as the psychological treatment of choice for obsessive-compulsive disorder (OCD). Uncertainty remains however about the magnitude of the effect of CBT with ERP and the impact of moderating factors in patients with OCD. Method: This systematic review and meta-analysis assessed randomised-controlled trials of CBT with ERP in patients of all ages with OCD. The study was preregistered in PROSPERO (CRD42019122311). The primary outcome was end-of-trial OCD symptom scores. The moderating effects of patient-related and study-related factors including type of control intervention and risk of bias were examined. Additional exploratory analyses assessed the effects of treatment fidelity and impact of researcher allegiance. Results: Thirty-six studies were included, involving 2020 patients (537 children/adolescents and 1483 adults) with 1005 assigned to CBT with ERP and 1015 to control conditions. When compared against all control conditions, a large pooled effect size (ES) emerged in favour of CBT with ERP (g = 0.74: 95% CI = 0.51 to 0.97 k = 36), which appeared to diminish with increasing age. While CBT with ERP was more effective than psychological placebo (g = 1.13 95% CI 0.71 to 1.55, k = 10), it was no more effective than other active forms of psychological therapy (g = −0.05: 95% CI -0.27 to 0.16, k = 8). Similarly, whereas CBT with ERP was significantly superior when compared to all forms of pharmacological treatment (g = 0.36: 95% CI 0.7 to 0.64, k = 7), the effect became marginal when compared with adequate dosages of pharmacotherapy for OCD (g = 0.32: 95% CI -0.00 to 0.64, k = 6).A minority of studies (k = 8) were deemed to be at low risk of bias. Moreover, three quarters of studies (k = 28) demonstrated suspected researcher allegiance and these studies reported a large ES (g = 0.95: 95% CI 0.69 to 1.2), while those without suspected researcher allegiance (k = 8) indicated that CBT with ERP was not efficacious (g = 0.02: 95% CI -0.29 to 0.33). Conclusions: A large effect size was found for CBT with ERP in reducing the symptoms of OCD, but depends upon the choice of comparator control. This meta-analysis also highlights concerns about the methodological rigor and reporting of published studies of CBT with ERP in OCD. In particular, efficacy was strongly linked to researcher allegiance and this requires further future investigation.