How Effective Are Credible Sources in Changing Behavior? A Systematic Review with Meta-Analysis

This systematic review and meta-analysis investigated the unique effects of credible sources on performed behavior, rather than behavioral antecedents (i.e., attitudes), and contexts where it is most effective. Six databases were searched to June 2024, yielding 40 effect sizes ( N = 7,995, 58.42% females, mean age of 17.75 years old, with mostly White ethnicity 75.81%) from 34 papers. A random effects model indicated a small positive effect, d = 0.14 (95% CI [0.04, 0.23]). Moderator analyses showed significant positive effects when the credible source had a medical professional qualification, communicated with participants in-person, the intervention was verbal or combined verbal and written messages, when behavior occurred once, and immediately followed the intervention. Because of the small effect, the costs associated with generating credible sources should be balanced against their effectiveness.