Self-harm: The study assessed self-harm tendencies by asking: “In the past year, have you hurt yourself on purpose in any way?” Participants could answer: “No” or “Yes”, and the dichotomous response was used for analysis. Suicidal thoughts and behaviours: The study assessed suicidal thoughts or behaviours by using a truncated version of the Paykel (1974) Suicide Scale. Participants were asked: “Have any of the following happened in the past year?” followed by four response options including: • Have you felt like life was not worth living? • Have you thought of taking your life, even if you would not really do it? • Have you reached the point where you seriously considered taking your life or perhaps made plans how you would go about doing it? • Have you made an attempt to take your life? Participants could answer: “No” or “Yes” to each response option. A binary variable (“Yes”/”No”) was created where a participant counted as “Yes” if responded in the affirmative to at least one of the four response options above. These questions were self-completed to ensure respondent privacy but they were referred to available support services near them if they responded yes to any of the above items. Analysis approach: Associations between technology-facilitated child sexual exploitation and abuse and well-being indicators were examined using survey-weighted regression models, accounting for the complex survey design and sampling weights. Models were adjusted for child age and gender. For binary well-being outcomes, including self-harm and suicidal thoughts or behaviours, prevalence ratios were estimated using survey-weighted Poisson regression models with a log link and robust variance estimation. Results are presented as risk ratios (RRs) with 95 per cent confidence intervals. For continuous outcomes, including anxiety scores, survey-weighted linear regression models were used. Results are presented as percentage changes in the standardized outcome score. Through Children’s Eyes Appendix 90