Source credibility and patient participation intent in social media-based clinical trial recruitment: A cross-national study

Abstract Purpose: Social media is increasingly used for clinical trial recruitment, yet participant response to such recruitment remains inconsistent. This study examined the role of source credibility in shaping attitudes and behavioral intention to participate in clinical trials advertised through social media and assessed whether these relationships differ across regulatory environments. Materials and Methods: A cross-sectional survey was conducted among adults in the United States ( n = 298) and Germany ( n = 273). Source credibility, attitude, behavioral intention, perceived usefulness, and perceived ease of use were measured using previously validated scales adapted to the context of social media-based clinical trial recruitment. Structural equation modeling and multi-group analysis were performed. Results: Source credibility was the strongest predictor of attitude toward clinical trial advertising in both countries. In the United States, credibility also directly predicted behavioral intention and strengthened the relationship between attitude and participation intention. In Germany, credibility influenced attitude but showed no significant direct effect on behavioral intention. Perceived ease of use through perceived usefulness positively influenced attitudes in both countries. Conclusion: Source credibility plays a central role in shaping responses to social media-based clinical trial recruitment. Its influence varies across regulatory environments, suggesting that trust-building strategies should be tailored to local healthcare and regulatory contexts. The findings have implications for emerging markets, including India, where social media recruitment is expanding and where transparency, ethics committee oversight, and participant trust remain essential.