Functional Connectivity in Obsessive-Compulsive Disorder Before and After Psychotherapy

Obsessive-compulsive disorder (OCD) has been increasingly linked to alterations in functional connectivity (FC) across large-scale brain networks, particularly the default mode (DMN), salience (SN), and central executive network (CEN), known as the triple-networks. However, little is known about how connectivity patterns evolve following treatment. We examined both static and dynamic resting-state FC in 25 adults with OCD and 21 matched healthy controls (HCs) at baseline, one week, and three months following intensive exposure and response prevention (ERP) using the Bergen 4-Day Treatment (B4DT). Independent component analysis (ICA) and sliding-window approaches were used to evaluate network connectivity within and between the triple networks. At baseline, adults with OCD showed stronger static connectivity within the DMN and SN and spent more time in a dynamic connectivity state characterized by strong connectivity within the DMN and decoupling between the DMN and SN compared to controls. Following the 4-day intensive treatment, these abnormal patterns normalized and remained stable at the three-month follow-up. A higher number of transitions between states was associated with reductions in the severity of OCD, anxiety, and depressive symptoms. Additional correlation analyses indicated that higher baseline SN-CEN connectivity was associated with greater symptom severity, while post-treatment reductions in CEN and CEN-SN static connectivity were linked to improvements in depressive symptoms. These findings suggest that effective treatment promotes a normalization of both static and dynamic connectivity within and between the triple networks. Thus, dynamic metrics, alongside static measures, may serve as clinically meaningful biomarkers of therapeutic response.