 The subjects in both groups will be double-blindly randomized to receive either bupropion or placebo. The assignment to each group will be done randomly in order to ensure location concealment. For subjects receiving bupropion, the dose will be 150 mgd for the first three days, increasing for 150 mg twice daily, continued for a period of eight weeks. In case of intolerable side effects, the dosage will be decreased to 150 mg daily. 