Lando 1991.

Methods	Study design: Randomized controlled trial Country: USA Recruitment: Community volunteers Group size: 4 ‐ 16, typically 6 ‐ 11
Participants	353 smokers; 52% women, av. age 42, av. cpd 30 Therapists: Trained facilitators, mainly graduates, including some who had quit through clinic programme
Interventions	Both interventions included 16 x 45 ‐ 60‐min sessions over a 9 wk period. Nicotine fading schedule prior to quit date at 3 wks 1. Enriched cohesiveness intervention: included written commitments and exercises designed to facilitate positive group interaction 2. Standard group treatment
Outcomes	1‐yr sustained (relapse‐free) abstinence Validation: randomly selected subsample of those claiming abstinence tested for saliva TCN, but not clear whether reported data includes a correction for false reporting
Notes	No non‐group control. In comparison 2.3.2 evaluating group cohesion. Originally a factorial design comparing satiation and nicotine fading in addition to cohesiveness manipulation, but satiation arm abandoned. Only data for nicotine fading procedure arms reported in paper. P values reported in the paper were corrected for the design effects of clustering
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomly assigned by information group attended. 32 information meetings and 41 treatment groups
Allocation concealment (selection bias)	Unclear risk	No details given
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Partial validation, all participants received active intervention
Incomplete outcome data (attrition bias) All outcomes	Low risk	6.5% loss to follow‐up included in analyses