Zelman 1992.

Methods	Country: USA Recruitment: community volunteers
Participants	116 smokers (excludes 10 early treatment dropouts evenly distributed across conditions) 54% female, average age 29 to 35, average cpd 25 to 27
Interventions	1. Rapid smoking + support counselling 2. Rapid smoking + skills training 3. Nicotine gum 2 mg, average 10 pieces/day, duration not stated + skills training 4. Nicotine gum + support counselling Level of support: high (6 x 60‐ to 75‐min group sessions over 2 weeks, starting on quit day)
Outcomes	Sustained abstinence at 12 months (not more than 2 consecutive days of smoking) Validation: Independent observer report
Notes	No placebo. Group support variants collapsed; 3 and 4 compared to 1 and 2 Study was funded by National Institutes of Health
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "subjects were randomly assigned"
Allocation concealment (selection bias)	Unclear risk	Not stated
Blinding (performance bias and detection bias) All outcomes	High risk	Placebos not used
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Early dropout rates reported, but not included in the analyses. 4 12‐month dropouts included as smokers

AE = adverse event; ALA = American Lung Association; C = control; CBT = cognitive behavioural therapy; CO = carbon monoxide in exhaled air; cpd = cigarettes per day; COPD = chronic obstructive pulmonary disease; EOT = end of treatment; FTND = Fagerström Test for Nicotine Dependence; FTQ = Fagerström Tolerance Questionnaire; I = intervention; ITT = intention to treat; MA = meta‐analysis; RTQ = reduce‐to‐quit; OTC = over‐the‐counter; PP = point prevalence; SC = smoking cessation; TQD = target quit date