Cummings 1988.

Methods	Setting; stop smoking hotline, USA Recruitment: callers who accepted offer of a stop smoking booklet and who agreed to follow up
Participants	1895 smokers, 65% female, average age 42, average cpd 28, 89% had made at least 1 prior quit attempt
Interventions	First 4 groups received booklets of similar length (± 50 pages) and format, differing in precise instructions ∙ High structure (day‐by‐day plan) recommending 'cold turkey' quitting ∙ High structure recommending gradual reduction ∙ Low structure (menu of exercises) with gradual reduction ∙ Low structure, 'cold turkey' Control booklet: 15 pages stressing health effects of smoking
Outcomes	Abstinence from 1 month to 6 months; self‐report by telephone interview with blinded assessors No biochemical validation; confirmation by a significant other
Notes	1 to 4 vs 5 in main analysis
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomised; method not described
Allocation concealment (selection bias)	Unclear risk	No details given
Blinding (performance bias and detection bias) All outcomes	Low risk	Confirmation by significant other; booklets of similar length, so differential misreport unlikely
Incomplete outcome data (attrition bias) All outcomes	Low risk	Analyses based on participants reached at 1 month and 6 months' follow‐up; 89% of those randomised Dropout rates similar in all groups