This is a double-blind, placebo-controlled study, in which patients will receive treatment of Quetiapine XR for 8 weeks. All patients will receive Quetiapine XR at an initial dose of 50mg/day to be increased incrementally (dose of 50mg/day 2 and 150mg/day 3) to achieve a target dose of 300 mg/day by day 4. Tablets will be self-administered early each night. Patient's results will be compared to their own baseline measurements, in a double-blind fashion.