The effect of source expertise on the persuasiveness and sharing of health information on social media: A systematic review.

People increasingly rely on social media for health information, despite substantial variability in information quality. We conducted a systematic review and meta-analysis examining whether people are sensitive to source expertise when evaluating and sharing online health claims, and if this depends on whether the source is an individual expert (e.g., a physician) or an expert group (e.g., a health organisation). Three searches across four databases identified 25 individual studies published across 22 papers. From these studies, we found that people were only marginally more persuaded by health experts than nonexperts, and that this effect was not moderated by expert type (individual vs. group). However, we found tentative evidence that experts are more persuasive when accompanied by congruent credibility cues, but that expertise can backfire when these cues are incongruent. Evidence regarding people's sensitivity to source expertise when sharing was mixed, reflecting heterogeneity in study designs. This review highlights several limitations in the current literature, indicating the need for further research that accounts for how both experts and nonexperts are perceived in online health contexts. We discuss implications and propose several avenues for future research and potential interventions.