Impact of Exposure to Health Misinformation on Belief in Health Misinformation: A Meta-Analysis of RCTs

Health authorities have labeled health misinformation a major global health threat and academic scholars consider exposure to health misinformation a barrier to an individual's informed decision-making. However, quantitative evaluations of the persuasive impact of exposure to health misinformation produced mixed results. This study uses a meta-analytic approach to analyze the average impact of health misinformation across studies and explore potential moderators of effect size. The analysis includes randomized controlled trials that compare the impact of exposure to health misinformation on individuals' belief in misinformation with a neutral control group. The meta-analysis examined 31 effect sizes (<i>N</i> = 18,115) from 14 studies that showed that exposure to health misinformation, on average, increases individuals' belief in misinformation, <i>g</i> = 0.24, 95% Confidence Interval [0.10, 0.38]. Moderator analyses revealed that exposure to longer health misinformation was associated with stronger effects, <i>g</i> = 0.41, 95% CI [0.27, 0.55], than exposure to shorter statements, <i>g</i> = 0.06, 95% CI [-0.08, 0.20]. The effect size estimates can support fact-checkers in identifying potentially highly persuasive misinformation and can support researchers in conducting power-analyses and identifying reasonable smallest effect sizes of interest when studying the impact of health misinformation.