Meta-analytic examination of the strong and weak principles across 48 health behaviors.

OBJECTIVE The strong and weak principles of change state that progress from the precontemplation to the action stage of change is associated with a one standard deviation increase in the pros and a one-half standard deviation decrease in the cons of change. In this study these relationships, originally developed by Prochaska [Prochaska, J.O., 1994. Strong and weak principles for progressing from precontemplation to action on the basis of 12 problem behaviors. Health Psychology, 13, 47-51] based on an examination of 12 studies of 12 different behaviors, were re-examined using many more datasets and much more rigorous statistical methods. METHODS The current study analyzes 120 datasets from studies conducted between 1984 and 2003 across and within 48 health behaviors, including nearly 50,000 participants from 10 countries. The datasets were primarily analyzed utilizing meta-analytic techniques. RESULTS Despite the range of behaviors and populations, the results were remarkably consistent with the original results (pros=1.00 standard deviation, cons=0.56 standard deviation). Few potential moderators showed any impact on effect size distributions. CONCLUSIONS This updated and enhanced examination of two important principles of behavior change is a significant contribution to the field of multiple health risk behaviors, as it clearly demonstrates the consistency of the theoretical principles across multiple behaviors, which has implications for developing multiple health risk behavior interventions.