3d. What Do We Know About the Effectiveness of Behaviour Change Theories?  

In closing, this module introduces you to some of the more widely studied and applied theories purporting to explain the processes by which health-related behaviour change occurs. These theories have been applied extensively, especially in the United States, to guide the development of interventions aimed at encouraging individuals to adopt health-promoting behaviours (e.g., stop smoking, drink alcohol in moderation, make healthier food choices, be more physically active). But the body of evidence supporting the “effectiveness” of these theories as guidelines for the development of preventive interventions is relatively limited.

This pattern was confirmed in a meta-analysis conducted by Prestwich et al, one of your optional readings for this week.¹ The authors reviewed 190 documented interventions promoting physical activity and healthy eating. Type of theory and extent of application were assessed using a coding scheme developed by the authors, and meta-regression techniques were used to test the association between theory application and reported intervention effectiveness.

Just over half (56%) of the interventions reviewed were reportedly based on theory, but the vast majority (90%) of these did not describe linkages between theory and their behaviour change interventions. Moreover, the majority of analyses failed to reveal any association between theory use and intervention effectiveness. Interventions based on social cognitive theory or the transtheoretical (stages of change) model were no more effective than interventions that did not report a theory base.

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It’s important to note that this finding does not necessarily point to key shortcomings or limitations of behaviour change theories (although the collective body of behaviour change theories do suffer from key limitations that will be explored in greater detail in Module 4). Rather, it underscores the need to apply theories in a comprehensive way that clearly specifies linkages between theoretical components and intended outcomes.^{2, 3} Population-level interventions that fail to do this can expect to achieve equally dismal results.