Notwithstanding the logistical and ethical issues that make this sensitive research difficult to accomplish, we agree that prospective investigations of children followed from early childhood offer the best prospect for identifying mechanisms underpinning the relationship between childhood adversity and later outcomes such as mental health, social functioning, and educational/occupational attainment.

In response to the query regarding how this important research might be achieved given the challenges Sim et al identified, we suggest that longitudinal, population record-linkage studies offer excellent capacity to examine these relationships in an unbiased, inclusive, and ethical manner. One such investigation is the New South Wales Child Development Study (http://nsw-cds.com.au) based at the University of New South Wales. This is a longitudinal investigation following the development of a cohort of 87 026 children who entered full-time schooling in 2009 (representing 99.9% of the population). Via local record-linkage infrastructure provided by the Centre for Health and Record Linkage (http://www.cherel.org.au), and operated under strict privacy provisions, anonymised multi-agency records on the children (including health, education, welfare, birth, and developmental records) have been combined by researchers with records on their parents (including health and criminal records).

As part of this study, diverse measures of childhood adversity are available from population-based government child-protection files. Records were available for 3926 children (4.5%) in the cohort by the age of 5 years. These records, in combination with linked information on mental health and well-being outcomes in childhood (and, in due course, in adolescence and adulthood), offer an excellent opportunity to determine the childhood, adolescent, and adult sequelae of early exposure to adversity. Publications from the initial phase of the investigation (spanning birth to 5 years in the population cohort) are currently in preparation.