Garvey 2000.

Study characteristics
Methods	Study design: parallel RCT Country: USA Recruitment: community volunteers
Participants	608 smokers, aged > 20, smoking > 5 cigarettes per day 49% men, average cigarettes per day: 23
Interventions	1) 4 mg nicotine gum (recommended 9 to 15 pieces), weaning from 2 months 2) 2 mg nicotine gum, use as described for group 1 3) Placebo gum All received brief counselling (5 to 10 minutes) at each study visit (1, 7, 14, 30 days, 2, 3, 6, 9, 12 months)
Outcomes	Sustained abstinence at 12 months (relapse defined as 7+ consecutive days or episodes of smoking) Validation: CO ≤ 8 ppm Adverse events: not measured
Notes	This study was supported by grants DA06183 and DA10073 from the National Institute on Drug Abuse, and by the Department of Veterans Affairs. Conflicts of interest: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Stratified by dependence level (high/low) and then allocated [Quote]: "using a randomized, double‐blind procedure"
Allocation concealment (selection bias)	Unclear risk	No further detail
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Described as double‐blind, but no further information
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Relapsers were included as failures. Dropout rates not reported