Hall 1984

Methods	Setting: clinic, USA Recruitment: media adverts and referral
Participants	135 smokers; 59% female, average age approximately 36, average cigs/day 29 Therapists: 2 psychologists, randomly assigned to groups
Interventions	2 × 2 factorial trial, aversive smoking conditions collapsed 1. Skills training, 14 × 75 minute sessions. 8 sessions over 3 weeks involved 6 seconds or 30 seconds of aversive smoking. 6 sessions over week 1 to 6 covered relaxation, commitment and cost benefits, and relapse prevention skills with role‐play of risk situations 2. Discussion control. Same aversive smoking. Other 6 sessions used self‐scoring tests and group discussion. Discussion of specific skills discouraged
Outcomes	Abstinence at 12 months (point prevalence) Validation: CO < 10 ppm, plasma thiocyanate < 85 ng/mg and confirmation from significant other
Notes	Matched for contact time Author tested for therapist and cohort main effects. None significant
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomisation method not described
Allocation concealment (selection bias)	Unclear risk	No details given
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	No details given
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Biochemical validation used
Incomplete outcome data (attrition bias) All outcomes	Low risk	8 dropouts from group 1 and 4 from group 2 before start of relapse prevention sessions reincluded in this analysis