Purpose
Sexual minority adolescents face well-documented disparities in terms of peer victimization and mental health. Less is known about how these disparities emerge and change throughout childhood. Providing prospective evidence on sexual minorities’ peer victimization and mental health from early childhood through adolescence, the current study addresses this gap.

Methods
Analyses used data from the Fragile Families and Child Wellbeing Study, a population-based cohort study of children born in twenty American cities between 1998 and 2000. Teens reported sexual minority status during interviews conducted (primarily by phone) between 2014 and 2017. Multivariate regression analyses examined disparities in peer victimization and mental health at ages 5, 9, and 15.

Results
Compared to their peers, sexual minorities experienced similar rates of peer victimization at age 5 but substantially higher rates at ages 9 and 15. Sexual minority children's elevated bullying rates at age 9 were confirmed using independent reports from both parents and the children themselves. Disparities in depressive/anxious symptoms were not documented until age 15, at which time large disparities were reported across three diagnostic scales and two measures of professional diagnosis/treatment. Both current and prior peer victimization were robust predictors of adolescent mental health, explaining about 20% of the disparities between sexual minority teens and their peers.

Conclusions
Sexual minority children's social vulnerabilities appear to emerge between ages 5 and 9, followed by the emergence of mental health disparities between 9 and 15. Results underscore the importance of intervening early to prevent the emergence of bullying behaviors.