Abstract
<p>Importance: Concerns about the risks adolescents face online are rising, but existing research on online harms typically examines limited outcomes, rarely allows for platform-specific comparison, and lacks practical standardized measurement that would be suitable for public health monitoring.Objective: We introduce and implement a measurement approach estimating the prevalence of negative experiences among US adolescents online, offline, and by platform.Design, Setting, and Participants: Cross-sectional, nationally representative, probability-based survey of US adolescents aged 13-17 conducted February-December 2025 through the Understanding America Study panel. Self-reported use of 20 online platforms (e.g. Facebook, Instagram, Snapchat, TikTok, YouTube, Facetime, email etc) was assessed.Main Outcomes and Measures: Self-reported prevalence of major risks and harms experienced in past 4 weeks, including harassment, sexual solicitation, and exposure to violent or self-harm content, as well as sleep disruption (measured online, offline, and by platform). Survey-weighted logistic regression identified associated factors.Results: Weighted sample included 482 adolescents (mean age 15 years; 47.1% female; 65.1% White) from 47 US states. Across online and offline contexts, 44.3% witnessed harassment and 29.6% had experienced it directly in the past 4 weeks. Overall prevalence varied by gender and age: girls were more likely than boys to feel worse about themselves due to others' posts, messages, or communications (29.1% vs 15.5%), and older adolescents (ages 15-17) were more likely than younger adolescents (ages 13-14) to have witnessed discrimination against others (48.6% vs 38.5%). Online exposure exceeded offline exposure for numerous harms, including exposure to violent imagery (10.5% vs 1.6%), unwanted sexual images (13.5% vs 2.0%), and content encouraging self-harm (9.6% vs 5.1%). More than half (51.7%) reported sleep disruption due to technology use. Parental education, income, and parental controls were not significantly associated with online harm exposure (all P &gt; .05). Platform differences in exposure to some harms were substantial, e.g., 42.8% of TikTok users and 28.3% of Instagram users attributed disrupted sleep to those platforms, compared with 11.3% of text-messaging users and 0.6% of email users.Conclusions and Relevance: Negative online experiences are common among US adolescents and vary by platform, gender, and age. Establishing rigorous, multi-layered measurement approaches with platform-by-platform, social media versus other digital environments, and online versus offline comparisons is essential for transforming fragmented evidence into actionable data that can guide effective decisions by youth, parents, platforms andregulators.</p>