As researchers, clinicians and health systems strive to understand and improve mental health and well-being in youth, the parameters by which mental illness itself is defined have increasingly become the topic of inquiry. In the March 2015 issue of SPPE, Roberts et al. (Soc Psychiatry Psychiatr Epidemiol 50(3):397-406, 2015) integrate DSM diagnostic criteria with impairment in adolescents, showing that the latter is more frequent in full-syndrome disorders but still relevant for sub-threshold conditions, which have higher overall prevalence. These findings shift the focus away from specific diagnostic criteria and thresholds, and towards the backdrop of distress and impairment in young people. They also have implications for staging models and clinical services for youth mental health, particularly for prevention and early intervention efforts.