Behavioral inhibition/activation system in obsessive-compulsive disorder: brain morphometric correlates and treatment outcomes.

The behavioral inhibition/activation system (BIS/BAS) has been implicated in a range of psychiatric disorders, yet its role in obsessive-compulsive disorder (OCD) remains unclear. Integrating self-report measures, neuroimaging, and clinical interventions, we explored how BIS/BAS contribute to OCD psychopathology. Patients with OCD showed elevated BIS and reduced BAS drive sensitivity, with BIS tracking symptom severity. BIS was indirectly associated with obsession and compulsion symptoms via right supramarginal gyrus sulcal depth and right-lateralized thalamic volume, respectively, with the BIS-thalamus association emerging as a key brain morphometric association pattern distinguishing patients with OCD from healthy controls. In addition, BIS decreased following selective serotonin reuptake inhibitor treatment, with reductions correlating with OCD symptom improvement, and BAS increased following cognitive behavioral therapy. In summary, our findings suggest distinct contributions of BIS and BAS to OCD psychopathology and identify them as clinically relevant dimensions for future investigation.