Back to the drawing board? A review of applications of the transtheoretical model to substance use.

The transtheoretical model (TTM) is still enormously popular with practitioners, clinicians and many researchers in the addictions field. However, in a recent years a number of commentators have criticized aspects of the model and the research based on it. This paper extends a recent critique of the TTM as applied to smoking cessation to include applications of the model to cessation or reduction of alcohol or drug use. The first section discusses measures of the central construct of stages of change and notes a number of serious problems. Staging algorithms are based on arbitrary time periods and some are logically flawed. In the case of multi-dimensional questionnaires (the URICA, the SOCRATES and the RCQ), the pattern of correlations among the subscales shows that they are not measuring discrete stages of change. The one study to date that has compared the two different methods found low concordance, which is probably due to incompatible stage definitions. In the second section of the paper, the evidence base for the TTM is reviewed. The review is organized by the four research designs that have been used to test predictions from stage models: cross-sectional comparisons of people in different stages; examination of stage sequences; longitudinal prediction of stage transitions; and experimental studies of matched and mismatched interventions. It concludes that current evidence for the model as applied to substance use is meagre and inconsistent. Researchers are urged to develop better stage models.