Role of pre-existing adversity and child maltreatment on mental health outcomes for children involved in child protection: population-based data linkage study.

Objectives: To determine mental health outcomes for children with a history of child protection system involvement, accounting for pre-existing adversity, and to examine variation in risk across diagnostic groupings and child protection subgroups.

Design: A longitudinal, population-based record-linkage study.

Participants: All children in Western Australia (WA) with birth records between 1990 and 2009.