The patients will begin treatment with duloxetine 30 mg/day at visit 2 and will be titrated to 60 mg/day at visit 3 (2 week since drug dispensed). The dosage will be maintained on 60 mg/day for 6 more weeks. During the period, the patients will receive periodic evaluations at visit 2 (0 week drug dispensed), 3 (2 week since drug dispensed), 4 (4 weeks since drug dispensed), and 5 (8 weeks since drug dispensed). The patients will receive fMRI examination at baseline and at the end of the 8-week treatment.