BackgroundA high proportion of young people in prison have a history of abuse and neglect, and/or of neurodevelopmental or psychiatric conditions. Despite this, the only two conditions specifically associated with abuse and neglect, Reactive Attachment Disorder (RAD) and Disinhibited Social Engagement Disorder (DSED), have never been included as part of a comprehensive prevalence study. MethodsA cross sectional study, in 110 male inmates aged 16 to 23, examined the prevalence of, and associations between, adverse childhood experiences (ACEs), neurodevelopmental and mental health conditions, including RAD and DSED. OutcomesVirtually all of the young men (96 %) had one or more lifetime neurodevelopmental or mental health conditions, 85.5 % had a current condition, yet less than 3 % reported having received a mental health assessment in prison. High rates of RAD and/or DSED symptoms were found (53.6 %) and 74.5 % had experienced some form of abuse or neglect. InterpretationThere is a high prevalence of ACEs, RAD/DSED, neurodevelopmental and other mental health conditions within this population. Comprehensive clinical assessments are required to ensure appropriate support and staff training is needed to ensure that the full implications of the high prevalence of neurodevelopmental and mental health conditions are understood as part of trauma informed care.