Trajectories of Persistent Exposure to Self-Harm-Encouraging Websites and Subsequent Mental Health Outcomes in US Youth: Longitudinal Cohort Study.

BACKGROUND: Self-harm, including suicidal thoughts, self-injurious behavior, and disordered eating, is a major public health concern among adolescents and young adults. Youth increasingly encounter self-harm-related content online, including websites that explicitly encourage harmful behaviors. Although exposure to such content has been linked to poorer mental health, most research is cross-sectional and has not examined longitudinal exposure trajectories. Whether persistent exposure represents a distinct digital risk pattern remains unclear. OBJECTIVE: This study examined longitudinal trajectories and correlates of exposure to self-harm-encouraging websites over 1 year and tested whether persistent exposure was associated with subsequent suicidal ideation, self-injury, and disordered eating. METHODS: We analyzed data from 2197 US youth aged 13 to 22 years who completed waves 2 and 4 of Project Lift Up, a national longitudinal cohort study. Website exposure was categorized into 4 trajectories: none, desist (wave 2 only), new (wave 4 only), and persistent (both waves). Categories reflected reported exposure at the 2 assessment waves rather than the frequency or continuity of website use between assessments. Logistic regression models estimated associations between exposure trajectory and wave 4 suicidal ideation, self-injury, and disordered eating, restricting analyses to participants without the respective outcome at wave 2. Models were adjusted for demographics and wave 2 depression or anxiety symptoms and other mental health indicators. RESULTS: Overall, 26.5% (583/2197) reported exposure to self-harm-encouraging websites at wave 2, and 18.5% (407/2197) reported persistent exposure. Privacy concerns, embarrassment, curiosity, and lack of offline support were associated with greater odds of persistence (adjusted odds ratios [aORs] 1.84-3.23), whereas accidental exposure was associated with lower odds of persistence (aOR 0.28, 95% CI 0.19-0.41). Compared with no exposure, persistent exposure was associated with higher odds of suicidal ideation (aOR 1.88, 95% CI 1.24-2.86; P=.003), self-injury (aOR 3.14, 95% CI 2.05-4.80; P<.001), and disordered eating (aOR 2.46, 95% CI 1.54-3.93; P<.001). Adjusted predicted probabilities showed a graded pattern, with persistent exposure associated with the highest predicted probabilities (suicidal ideation: 33.4% vs 21.3%; self-injury: 25.7% vs 10.2%; disordered eating: 11.7% vs 5.3%). New exposure was associated with increased odds of self-injury (aOR 2.32, 95% CI 1.30-4.15; P=.004) but was not significantly associated with suicidal ideation or disordered eating. The desist trajectory was not significantly associated with outcomes. CONCLUSIONS: Persistent exposure to self-harm-encouraging websites may represent a distinct digital risk pattern associated with higher subsequent odds of suicidal ideation, self-injury, and disordered eating. Assessing patterns of repeated website exposure and youths' motivations for seeking this content-not merely whether exposure occurred-may improve the identification of youth at heightened risk and inform digital prevention and clinical intervention strategies.