Pederson 1975.

Methods	Country: Canada. Study sites: not stated Study period: not stated. Recruitment: community volunteers. Sample size calculation: not mentioned.
Participants	Number of participants: 48 smokers (16 in each group). Inclusion criteria: not stated. Exclusion criteria: not stated. Overall demographics: 50% male; mean age: 37.9; mean years smoked: 17.25 and mean baseline smoking rate: 25.37 CPD.
Interventions	a) Waiting list control (contacted by telephone at 1, 3 and 10 months) [Not used in analyses]. b) Counselling (discussions about quitting techniques). c) Hypnosis and counselling (same discussion sessions and one 1.5 hour session of group hypnosis of simple relaxation techniques and benefit of quitting). Both groups b) and c) received 6 weekly group counselling sessions followed by 6 monthly meetings Duration of intervention: approximately 7.5 months. Duration of follow‐up: 10 months.
Outcomes	Definition of smoking cessation: abstinence for at least 3 months at 10‐month follow up. Adverse events: no information provided on whether or not AE data were collected and whether any AEs occurred.
Notes	Funding: Ontario Thoracic Society. Author declaration of interest: not reported. Additional notes: this study and Pederson 1979, Pederson 1980 were undertaken by same authors and funded by the same party.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomized, method not stated
Allocation concealment (selection bias)	Unclear risk	No details given
Blinding of outcome assessment (detection bias) All outcomes	High risk	Blinding not possible, self‐report only
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	All subjects were included in the analysis, but it is unclear whether anyone was lost to follow up, or whether the authors made some imputation to the missing outcome data.
Selective reporting (reporting bias)	Low risk	All outcomes reported as planned in the methods section