A 28-year-old woman presents with a 3-year history of intrusive thoughts about contamination and a fear that she will harm her family members. She spends 2–3 hours daily washing her hands and cleaning her home, which provides temporary relief but the anxiety returns within hours. She recognizes these thoughts as irrational and is distressed by them. Her Yale-Brown Obsessive Compulsive Scale (Y-BOCS) score is 32. She has never received any treatment. What is the most appropriate next step in management?