Eight studies (n=939) were included in the review: five randomised controlled trials (RCTs), and three pre-test/post-test non equivalent group design with a control group. One RCT was reported to be double-blind, and three RCTs were reported to be single blind.
Smoking cessation: One RCT reported higher cessation rates among participants receiving incentives to quit smoking and remain abstinent compared with the control group. However, five studies found no significant differences between smoking cessation treatment groups and control groups at the end of treatment. None of the five studies reporting on follow-up found any significant sustained treatment effects (continued abstinence) among participants.
Smoking reductions: Mixed results were reported for smoking reductions. Three RCTs reported significant reductions from baseline for the average number of cigarettes smoked per day and reductions in carbon dioxide levels for smoking cessation treatment groups compared to control groups. However, one RCT reported a significant increase from baseline in carbon dioxide levels and urine cotinine levels in the smoking cessation treatment group, while two studies found no significant differences in carbon dioxide levels.
Drug use outcomes: Smoking cessation treatment was not associated with increased drug use. Significant reductions were reported in the urge to use substances (one study). Significant decreases in rates of opiate and cocaine use were reported among participants who achieved smoking abstinence (one study) during smoking cessation treatment. However, three studies found no significant changes in substance use during the smoking cessation treatment period.
Gender differences: Only two studies reported on gender differences and reported inconsistent results for treatment outcomes.