Participants in this double-blind, placebo-controlled study will be randomly assigned to receive either the NTP (21 mg/day) and placebo or the NTP and bupropion SR (300 mg/day). Participants will begin taking one pill each day of bupropion SR (150 mg/day) or placebo at the start of the second week of the study. After three days, the dose of bupropion SR or placebo will increase to 2 pills each day. Participants will continue this dosing regimen until the end of Week 10. Throughout the 10-week study, participants will receive weekly group therapy.