<qa>  How many weeks are participants randomly assigned to receive either bupropion or placebo?Participants are randomly assigned to receive either bupropion or placebo for 12 weeks. Participants are assessed at baseline and at Weeks 2, 3, 4, 5, 6, 8, 10, and 12. Self administered questionnaires and interviews are used to assess participants. Follow-up assessments are made 1, 3, and 6 months after study completion. 