Killen 2008.

Methods	Study design: Randomized controlled trial Setting: Community cessation clinic, USA Recruitment: Community volunteers
Participants	301 smokers (≥ 10 cpd or 3.5 packs/wk) (excludes 3 participants who received wrong treatment); 40% women, av. age ˜46, av. cpd ˜20
Interventions	Therapists: 'one of three staff interventionists trained and supervised by the study psychologist and psychiatrist who had previous training in behavioral therapy' All participants received 6 x 30‐min individual CBT sessions at baseline, TQD, 1, 2, 4, 6 wks, and combination pharmacotherapy (Bupropion (300 mg, 9 wks) and NRT (21 mg patch, 8 wks incl tapering)) 1. Extended therapy: 4 x 30‐min sessions at 8, 12, 16, 20 wks, and weekly check in calls to automated system; report of relapse or craving prompted proactive calls 2. Standard therapy: 5‐min general support calls at 8, 12, 16, 20 wks
Outcomes	Abstinence at 52 wks (7‐day abstinence at both 20 and 52 wks) (Continuous abstinence also reported but not used in MA as could underestimate any effect on recycling) Validation: CO < 10 ppm (11 self‐reported quitters no longer living in study area accepted as quitters without validation)
Notes	New for 2016 update. Tested extended duration therapy, contributes only to comparison of counselling intensity (Analysis 2.1)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomized using a permuted block method (block size = 4), stratified on gender
Allocation concealment (selection bias)	Low risk	Participants assigned to next available ID number in corresponding gender. Researchers and participants were blinded to extended treatment assignment to the end of the open‐label phase
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Biochemical validation of abstinence
Incomplete outcome data (attrition bias) All outcomes	Low risk	89% followed up in standard‐care group, 90% followed up intervention group