RESUMEN
The Transtheoretical Model (TTM) proposes that stage matching improves the effectiveness of behaviour change interventions, such as for smoking cessation. It also proposes that standard smoking cessation interventions are matched to the relatively few smokers in the preparation stage and will not assist the majority of smokers, who are in the precontemplation or contemplation stages. This study tested the hypothesis that stage-matched interventions increase movement through the stages relative to interventions not stage-matched. It also tested the hypothesis that the relative effectiveness of stage-matched interventions is greater for people in precontemplation or contemplation (stage-matched for TTM but not for control) than for people in preparation (where both intervention and control were stage-matched). A total of 2471 UK adult smokers were randomised to either control or TTM-based self-help intervention and followed up 12 months after beginning the programme. Content analysis of the intervention and control self-help interventions examined whether control interventions were action-oriented, meaning they emphasised the processes of change relevant for preparation and action. Participants in the TTM arm were slightly more likely to make a positive move in stage, but this was not significant. There was no evidence that the TTM-based intervention was more effective for participants in precontemplation or contemplation than for participants in preparation. There was no evidence that TTM-based interventions were effective in this trial. The control intervention advocated process use appropriate for all stages and was not action-orientated. Stage matching does not explain the modest effects of TTM-based interventions over control interventions observed in some trials. These effects may instead have occurred because TTM-based interventions were more intensive than control interventions.