The Child Outcome Rating Scale: validating a four-item measure of psychosocial functioning in community and clinic samples of children aged 10-15.

Psychosocial functioning is considered an important and valued outcome in relation to young people's mental health as a construct distinct from psychiatric symptomology, especially in the light of an increasing focus on transdiagnostic approaches. Yet, the level of psychosocial functioning is rarely directly asked of young people themselves, despite the widespread recognition that the young person's perspective is valuable and is often at odds with those of other reporters, such as parents or professionals. One possible reason for this is that the field lacks a clear agreed tool to capture this information in a non-burdensome way. To begin to address this gap, this paper describes psychometric analysis of the Child Outcome Rating Scale (CORS), a brief and highly accessible self-report measure of young people's psychosocial functioning already used extensively by mental health professionals around the world but with only limited data on psychometric robustness. Using large community (n = 7822) and clinic (n = 2604) samples, we explore the factor structure, construct validity, internal consistency, differential item functioning, and sensitivity of the CORS. We found that the CORS stands up to psychometric scrutiny, having found satisfactory levels of reliability, validity, and sensitivity in this sample. We also found that the CORS is suitable for use with young people as old as 15 years old. That the CORS has been found to be psychometrically robust while being highly feasible (brief, simple, easy to administer) for use in busy clinical settings, combined with the fact that the CORS has already been widely adopted by clinicians and young people, suggests CORS may be an important tool for international use.