A systematic review and meta-analysis: Memantine augmentation in moderate to severe obsessive-compulsive disorder

•We found that 20 mg/day memantine augmentation to first-line pharmacological treatment for a period of at least 8 weeks is an effective intervention for moderate to severe OCD.•Stratification by refractoriness to first line treatment (serotonin reuptake inhibitors) demonstrated significant reduction of mean Y-BOCS score in both populations with no evidence of memantine augmentation favouring either of the groups.•Stratification by the target dose of memantine augmentation exhibited significant reduction of mean Y-BOCS score in both 20 and <20 mg/day populations, but a more favourable outcome was observed in the 20 mg/day group.•The subgroup of OCD patients with no comorbid disorders appeared to exhibit a more favourable response to memantine augmentation than those with comorbid symptoms.•Memantine was generally well tolerated and the reported adverse effects were mild and transient.