Carlo DiClemente

The Transtheoretical Model (TTM), developed by Carlo DiClemente and James O. Prochaska, describes behavior change as progressing through five stages: precontemplation, contemplation, preparation, action, and maintenance. The model was originally developed through research on how smokers quit, often without formal treatment.

The stages are precontemplation (no intention to change), contemplation (aware of the problem and considering change), preparation (intending to act soon), action (actively modifying behavior), and maintenance (sustaining the change and preventing relapse). DiClemente and Prochaska also described a recycling process through which people often revisit earlier stages.

DiClemente co-authored the widely cited trade book "Changing for Good" (1994) with James Prochaska and John Norcross, which presented the stages-of-change model to general audiences. His academic works include "Addiction and Change" (2006), which applies TTM to both the development of and recovery from addictive behaviors.

TTM has been applied to smoking cessation, weight management, exercise adoption, and substance abuse treatment. It is used to match interventions to an individual's current stage—for example, motivational interviewing techniques are often recommended for people in precontemplation or contemplation, while action-oriented strategies target those in the preparation or action stages.