Transtheoretical Model

The transtheoretical model in health psychology is intended to explain or predict a person's success or failure in achieving a proposed behavior change, such as developing different habits. It attempts to answer why the change "stuck" or alternatively why the change was not made.

The transtheoretical model is also known by the acronym "TTM" and by the term "stages of change model". A popular book and articles in the newsmedia    have discussed the model. It is "arguably the dominant model of health behaviour change, having received unprecedented research attention, yet it has simultaneously attracted exceptional criticism".

History and core constructs of the model
James O. Prochaska of the University of Rhode Island and colleagues developed the transtheoretical model beginning in 1977. It is based on an analysis of different theories of psychotherapy, hence the name "transtheoretical." The original model consisted of four variables: "preconditions for therapy," "processes of change," "content to be changed," and "therapeutic relationship".

Prochaska and colleagues later refined the model on the basis of research that they published in peer-reviewed journals and books. By 1997, the model consisted of five "core constructs": "stages of change," "processes of change," "decisional balance," "self-efficacy," and "temptation".

Stages of change
In the transtheoretical model as of 1997, change is a "process involving progress through a series of six stages" :
 * Precontemplation - "people are not intending to take action in the foreseeable future, usually measured as the next 6 months"
 * Contemplation - "people are intending to change in the next 6 months"
 * Preparation - "people are intending to take action in the immediate future, usually measured as the next month"
 * Action - "people have made specific overt modifications in their life styles within the past 6 months"
 * Maintenance - "people are working to prevent relapse," a stage which is estimated to last "from 6 months to about 5 years"
 * Termination - "individuals have zero temptation and 100% self-efficacy... they are sure they will not return to their old unhealthy habit as a way of coping"

In addition, the researchers conceptualized "relapse" which is not a stage in itself but rather the "return from action or maintenance to an earlier stage".

Processes of change
The 10 processes of change are "covert and overt activities that people use to progress through the stages". These processes are most emphasized at different transitions between stages of change :
 * For movement from precontemplation to contemplation, the processes of "consciousness raising," "dramatic relief," and "environmental reevaluation" are emphasized.
 * Between contemplation and preparation, "self-reevaluation" is emphasized.
 * Between preparation and action, "self-liberation" is emphasized.
 * Between action and maintenance, "contingency management", "helping relationship," "counterconditioning," and "stimulus control" are emphasized.

Prochaska and colleagues state that their research related to the transtheoretical model suggests that interventions to change behavior must be "stage-matched," that is, "matched to each individual’s stage of change".

Decisional balance
This core construct "reflects the individual’s relative weighing of the pros and cons of changing".

Self-efficacy
This core construct is "the situation-specific confidence people have that they can cope with high risk situations without relapsing to their unhealthy or high risk habit".

Temptation
This core construct "reflects the intensity of urges to engage in a specific habit when in the midst of difficult situations".

Controversy
Among the criticisms of the model are the following:
 * Little experimental evidence exists to suggest that application of the model is actually associated with changes in health-related behaviors.
 * In a systematic review published in 2003 of 23 randomized controlled trials, the authors determined that "stage based interventions are no more effective than non-stage based interventions or no intervention in changing smoking behaviour".
 * A second systematic review from 2003 asserted that "no strong conclusions" can be drawn about the effectiveness of interventions based on the transtheoretical model for the prevention of pregnancy and sexually transmitted disease.
 * A 2005 systematic review of 37 randomized controlled trials claimed that "there was limited evidence for the effectiveness of stage-based interventions as a basis for behavior change".
 * According to a randomized controlled trial published in 2006, a stage-matched intervention for smoking cessation in pregnancy was more effective than a non-stage-matched intervention, but this finding could have resulted from the "greater intensity" of the stage-matched intervention.
 * A randomized controlled trial published in 2009 found "no evidence" that a smoking cessation intervention based on the transtheoretical model was more effective than a control intervention that was not tailored for stage of change.
 * A 2009 review stated that "existing data are insufficient for drawing conclusions on the benefits of the transtheoretical model" as related to dietary interventions for people with diabetes.
 * "Arbitrary dividing lines" are drawn between the stages.
 * The model makes predictions that are "incorrect or worse than competing theories".
 * The model "assumes that individuals typically make coherent and stable plans," when in fact they do not.
 * The algorithms and questionnaires that researchers have used to assign people to stages of change have not been standardized, compared empirically, or validated.
 * The designs of many studies supporting the model have been cross-sectional, but longitudinal study data would provide stronger causal inferences.
 * In a 2002 review, the model's stages were characterized as "not mutually exclusive"; furthermore, there was "scant evidence of sequential movement through discrete stages".

Responses to such criticisms include:
 * Many studies that show the model to be ineffective have tailored interventions only to stage of change; if the studies had tailored interventions based on all core constructs of the model, they might have shown positive findings . In particular, the "processes of change" have been characterized as "under-researched" . A 2007 meta-analysis of tailored print health behavior change interventions found that the "number and type of theoretical concepts tailored on," including stage of change and processes of change, were associated with behavior change . In 2008 Hutchison and colleagues published a systematic review of 34 articles examining 24 interventions based on the transtheoretical model for behavior change in physical activity; only 7 of the 24 interventions addressed all four dimensions "stages of change," "processes of change," "decisional balance," and "self-efficacy".
 * Studies that find the model ineffective are poorly designed; for example, they have small sample sizes, poor recruitment rates, or high high loss to follow-up.
 * The conversion of continuous data into discrete categories is necessary for the model, similar to how decisions are made about the treatment of high cholesterol levels depending on the discrete category the cholesterol level is placed into.