Hayes 2018

Methods	Setting: mailed intervention, USA Recruitment: via state telephone quitlines
Participants	577 smokers (> 24 hour abstinence), 286 intervention and 291 control 27% male, average age 37, average cigs/day: 10 to 20
Interventions	Relapse prevention: 'Smoke‐free Kids' mailed parenting program Control: no treatment
Outcomes	30‐day point prevalence at 3 years Validation: self‐report only
Notes	Funding: "National Cancer Institute, National Institutes of Health, Grant No. R01CA148634." Declaration of interests: "The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article."
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Unclear how randomisation performed
Allocation concealment (selection bias)	Unclear risk	Allocation unclear
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Blinding unclear
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Self‐reported outcome only, but no face‐to‐face contact, hence differential misreport judged unlikely
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "Attrition status was not associated significantly with study group at either follow‐up point."