Sykes 2001.

Methods	Setting: cessation clinic, UK Recruitment: community volunteers interested in quitting
Participants	260 smokers, high proportion low socioeconomic status; 64% female, average age not stated, average cpd 25
Interventions	∙ Quit for Life ‐ cognitive‐behavioural manual, audiotape; gradual reduction pre‐quit day; stresses psychological addiction ∙ Stopping Smoking Made Easier ‐ leaflet, SoC‐based; abrupt quit
Outcomes	Abstinence at 12 months (Sykes 2001 reports 6 months) Validation: CO < 9 ppm
Notes	Comparison between self‐help materials; does not contribute to MA 1‐year data from Marks 2002
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Cluster‐randomised by orientation group attended; method not described
Allocation concealment (selection bias)	Unclear risk	Although potential for selection bias, "the receptionist was unaware of which intervention each group of participants would receive"
Blinding (performance bias and detection bias) All outcomes	Low risk	Biochemical validation; similar intensity of interventions
Incomplete outcome data (attrition bias) All outcomes	Low risk	15% loss to follow‐up at 1 year; similar across groups