Overall, 68% of the varenicline group and 67% of the placebo group completed the study. More participants in the varenicline group than in the placebo group quit smoking. During the last 4 weeks of treatment (weeks 9 to 12), 40% of those treated with varenicline had quit smoking compared with 16% in the placebo group. At the end of the 40-week follow-up, 20% of participants in the varenicline group continued to abstain from smoking compared with 10% in the placebo group. No differences were found between the groups in mood, anxiety, or thoughts about suicide, and depression did not worsen in either group. More patients in the varenicline group experienced nausea (27% vs. 10%).