Designing Social Media Health Warnings for Teenagers and Young Adults: A Randomized Clinical Trial.

Importance: Social media use is nearly ubiquitous among US teenagers and young adults and has been associated with increased risk for negative health outcomes such as depression and anxiety. Policymakers in several states have proposed or adopted policies requiring warnings on social media platforms. Objective: To test whether teenagers and young adults perceive that social media warnings discourage them from wanting to use social media and increase their awareness of the harms of social media. Design, Setting, and Participants: This within-participants randomized clinical trial was conducted online in December 2025 among US teenagers and young adults aged 13 to 29 years. Interventions: Participants viewed 15 messages shown in random order: 13 health warnings about different harms (eg, negative body image, and depression and anxiety), a screen time break warning similar to messages voluntarily displayed on some social media platforms, and a neutral control message. Messages were displayed on a mock social media page. Main Outcomes and Measures: Participants rated each message on a 1 to 5 scale for perceived message effectiveness for discouraging social media use (primary outcome) and awareness of the harms of social media (secondary outcome). Linear mixed models were used to estimate differences in outcomes between message topics, expressed as average differential effects (ADEs). Results: A total of 1012 participants (mean [SD] age, 19.3 [4.5] years; 509 women and girls [50%], 491 men and boys [49%], and 12 individuals who identified as nonbinary or another gender [1%]) completed the study. Participants perceived all health warnings as well as the screen time break warning as more effective than the control message (range of ADEs, 0.32 [95% CI, 0.24 to 0.41] to 0.62 [95% CI, 0.53 to 0.71]). Participants perceived all health warnings as more effective than the screen time break warning (range of ADEs, 0.16 [95% CI, 0.08 to 0.24] to 0.30 [95% CI, 0.22 to 0.37]), except for the health warning about addiction (ADE, 0.07 [95% CI, -0.004 to 0.14]). Similarly, participants perceived all warnings as increasing their awareness of the harms of social media more than the control message (range of ADEs, 0.19 [95% CI, 0.10 to 0.28] to 0.63 [95% CI, 0.54 to 0.72]) and all health warnings as increasing their awareness more than the screen time break warning (range of ADEs, 0.21 [95% CI, 0.13 to 0.28] to 0.44 [95% CI, 0.36 to 0.52]). Conclusions and Relevance: These findings of this randomized clinical trial suggest that requiring warnings on social media platforms could increase awareness of the harms of social media and discourage teenagers and young adults from wanting to use social media. Trial Registration: ClinicalTrials.gov Identifier: NCT07199660.