Effects of two psychotherapies for obsessive-compulsive disorder on brain activity during emotional processing

BACKGROUND: To clarify the working mechanisms of psychotherapy for obsessive-compulsive disorder (OCD), we studied the neural effects of two psychotherapies: cognitive behavioral therapy with exposure and response prevention (CBT-ERP) and inference-based cognitive behavioral therapy (I-CBT). METHODS: Fifty-five individuals with OCD completed an emotional processing task during fMRI before and after 20 weekly psychotherapy sessions, using general fear and OCD-related visual stimuli. We used Bayesian region-of-interest analyses to assess changes in brain activation in prefrontal, limbic, sensory, subcortical, and visual areas, and their association with symptom reduction. RESULTS: After treatment, both the CBT-ERP (N = 28) and I-CBT group (N = 27) showed strong credible evidence for increased activation of the lateral occipital cortex (LOC) and decreased activation of, amongst others, the dorsolateral prefrontal cortex in both the fear and OCD contrast. Symptom reduction was associated with activity decreases after CBT-ERP, mainly in the OCD contrast. Symptom reduction was associated with increased activity in the I-CBT group, particularly in the medial prefrontal cortex. Across all ROIs, higher baseline fear-related activity was associated with symptom reduction in CBT-ERP, while lower baseline activity was associated with symptom reduction in I-CBT in the precentral gyrus and dorsolateral prefrontal cortex. Lower baseline LOC activation during OCD-related stimuli was linked to symptom reduction after both psychotherapies. CONCLUSIONS: CBT-ERP and I-CBT showed overlapping changes in brain activity after treatment, although these changes related to symptom reduction in opposite directions, suggesting the two treatments achieve their effects through distinct mechanisms. Visual brain activity during emotional processing may predict treatment response across psychotherapies.