Etter 2004.

Methods	Setting: community, Switzerland Recruitment: mailing to population registers (not selected)
Participants	2934 smokers aged 15+, 74% pre‐contemplators, 40% tried to quit in previous year, 51% female, average age 36, average cpd 20
Interventions	∙ Tailored 8‐page letter plus SoC‐matched booklets; at 2 months, 4 months, 12 months ‐ repeat questionnaire to initiate further letter ∙ No intervention
Outcomes	Abstinence at 24 months (in maintenance stage; quit for > 6 months), 4 weeks; 7‐day abstinence also reported Validation: none
Notes	Tailored self‐help vs nothing; approximately half of group 1 received 1 letter only Effects at 6 months (Etter Arch Int Med 2001) not sustained at 24 months Relative difference smaller if shorter‐term abstinence used
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomisation: "list of random numbers"
Allocation concealment (selection bias)	Unclear risk	No details given
Blinding (performance bias and detection bias) All outcomes	High risk	"...members of the control group received a letter indicating that they had been attributed to that group..." No validation; intervention intensity higher than for control group
Incomplete outcome data (attrition bias) All outcomes	Low risk	Loss to follow‐up 14.0% in 1; 10.7% in 2 All non‐responders included in ITT analysis