Do cognitive functions in obsessive-compulsive disorder change after treatment? A systematic review and a double case report

Background: Neuropsychological and neuroimaging studies have documented that patients with obsessive-compulsive disorder (OCD) have cognitive difficulties dependent upon fronto-striatal circuits in the brain. It is, however, unclear whether the cognitive difficulties change after treatment. Answering this question could help establish whether cognitive difficulties in OCD are state dependent or more trait-like. Aim: To determine whether cognitive functions in OCD change after treatment, based on a systematic literature review, supplemented by a double case report of monozygotic twins with OCD. Methods: For the literature review, systematic searches were conducted in PubMed, Embase and PsycINFO from the earliest dates available to September 2010. For the double case report, monozygotic twins underwent blood samples and magnetic resonance imaging before treatment with cognitive behavioral therapy (CBT), antidepressants and small doses of antipsychotic medication. Before and after CBT they were assessed with measures of content and severity of OCD symptoms, and with a comprehensive battery of neuropsychological tests to assess cognitive functions. Results: Results from the studies under review (n = 14) were so inconsistent that it could not be concluded whether cognitive functions in OCD change after treatment. The twins improved some of their cognitive functions after treatment. Conclusions: A better understanding of whether cognitive dysfunctions in OCD are state dependent or trait-like could bring important implications in understanding the pathology and future treatment of OCD.