This PhD thesis investigates the mental and sexual health consequences of early-life challenges, specifically adverse childhood experiences (ACEs) and childhood gender non-conformity (i.e. experiences of not being able to meet societal gender norms and expectations). The thesis comprises four studies, based on baseline data from the nationally representative Danish Project SEXUS study and nationwide Danish registry data. 

Study 1 examined mental health disparities across sexual identity groups in relation to ACEs. Both ACEs and mental health problems varied significantly by sexual identity, with non-heterosexuals facing a higher burden of both. Notably, even non-heterosexuals without ACEs showed elevated risks of mental health problems compared to heterosexuals.

Study 2 explored the association between childhood gender non-conformity and mental health problems in the general population and across sexual identity groups. Regardless of sexual identity, gender non-conforming individuals reported more mental health problems than gender conforming peers.

Study 3 analyzed links of ACEs with sexual risk-taking behaviors and non-consensual sexual experiences among Danes aged 15-29 years. Exposure to ACEs was linked to more sexual risk-taking and a higher likelihood of non-consensual sexual experiences.

Study 4 assessed the impact of ACE on HPV vaccination uptake and compared sexual risk indicators between HPV-vaccinated and unvaccinated women. ACEs reduced HPV vaccination uptake among both girls, young women and boys, but no differences in sexual risk indicators were observed between HPV-vaccinated and unvaccinated women.

Overall, ACEs and childhood gender non-conformity are significant public health concerns due to their high prevalence and long-term impact on sexual and mental health.