Overall study characteristics
| Control groups reported* (n 33) | Control | MI groups reported* (n 34) | MI | |
| Mean (SD) or % (n) | Mean (SD) or % (n) | |||
| Total number of participants | 4694 | 4791 | ||
| % Females in study sample | 29 | 68 (27) | 30 | 68 (27) |
| % White people in study sample | 18 | 61 (37) | 19 | 57 (38) |
| Baseline age | 29 | 34 (13) | 30 | 35 (13) |
| Baseline cigarettes per day | 28 | 15 (6) | 28 | 16 (6) |
| Baseline sample size | 33 | 142 (147) | 34 | 141 (139) |
| Study included pharmacotherapy | 33 | 45% (n 15) | 34 | 47% (n 16) |
| Biochemical verification of abstinence | 33 | 82% (n 27) | 34 | 82% (n 28) |
| MI combined with other interventions | 34 | 74% (n 25) | ||
| Fidelity check conducted | 34 | 50% (n 17) | ||
| Duration of staff training in MI (in hours) | 11 | 52 (72) | ||
| Duration of MI intervention (in minutes) | 32 | 101 (122) | ||
| Variable | Papers reporting | Mean (SD)/% (n) | ||
| Publication year | 30† | 2004 (2.6) | ||
| Study conducted in the USA | 31 | 71% (n 22) | ||
| Cluster RCT | 31 | 16% (n 5) |
↵* Smith and colleagues30 reported on MI and control intervention effects for both low and high risk smokers. Both Hyman and colleagues31 and Ahluwalia and colleagues29 reported intervention effects for two different MI conditions, and Ahluwalia and colleagues29 also had two control conditions.
↵† 31 papers included, but one study consisted of unpublished data (Hannover and colleagues).
MI, motivational interviewing intervention; n, number of arms/papers; RCT, randomised controlled trial.