Recognizing that current frameworks for classification and treatment in psychiatry are inadequate, particularly for use in young people and early intervention services, transdiagnostic clinical staging models have gained prominence. These models aim to identify where individuals lie along a continuum of illness, to improve treatment selection and to better understand patterns of illness continuity, discontinuity and aetiopathogenesis. All of these factors are particularly relevant to help‐seeking and mental health needs experienced during the peak age range of onset, namely the adolescent and young adult developmental periods (i.e., ages 12‐25 years). To date, progressive stages in transdiagnostic models have typically been defined by traditional symptom sets that distinguish “sub‐threshold” from “threshold‐level” disorders, even though both require clinical assessment and potential interventions. Here, we argue that staging models must go beyond illness progression to capture additional dimensions of illness extension as evidenced by emergence of mental or physical comorbidity/complexity or a marked change in a linked biological construct. To develop further consensus in this nascent field, we articulate principles and assumptions underpinning transdiagnostic clinical staging in youth mental health, how these models can be operationalized, and the implications of these arguments for research and development of new service systems. We then propose an agenda for the coming decade, including knowledge gaps, the need for multi‐stakeholder input, and a collaborative international process for advancing both science and implementation.

In this article we have provided a perspective on the importance and value of youth mental health services for society and argued that advancing youth mental health services should be the number one priority of health services in Canada. Using the age period of 12-25 years for defining youth, we have provided justification for our position based on scientific evidence derived from clinical, epidemiological and neurodevelopmental studies. We have highlighted the early onset of most mental disorders and substance abuse as well as their persistence into later adulthood, the long delays experienced by most help seekers and the consequence of such delays for young people and for society in general. We have also provided a brief review of the current gross inadequacies in access and quality of care available in Canada. We have argued for the need for a different conceptual framework of youth mental disorders as well as for a transformation of the way services are provided in order not only to reduce the unmet needs but also to allow a more meaningful exploration of the nature of such problems presenting in youth and the best way to treat them. We have offered some ideas based on previous work completed in this field as well as current initiatives in Canada and elsewhere. Any transformation of youth mental health services in Canada must take into consideration the significant geographic, cultural and political diversity across the provinces, territories and indigenous peoples across this country.

Aim Youth mental health is of paramount significance to society globally. Given early onset of mental disorders and the inadequate access to appropriate services, a meaningful service transformation, based on globally recognized principles, is necessary. The aim of this paper is to describe a national Canadian project designed to achieve transformation of mental health services and to evaluate the impact of such transformation on individual and system related outcomes. Method We describe a model for transformation of services for youth with mental health and substance abuse problems across 14 geographically, linguistically and culturally diverse sites, including large and small urban, rural, First Nations and Inuit communities as well as homeless youth and a post‐secondary educational setting. The principles guiding service transformation and objectives are identical across all sites but the method to achieve them varies depending on prevailing resources, culture, geography and the population to be served and how each community can best utilize the extra resources for transformation. Results Each site is engaged in community mapping of services followed by training, active stakeholder engagement with youth and families, early case identification initiatives, providing rapid access (within 72 hours) to an assessment of the presenting problems, facilitating connection to an appropriate service within 30 days (if required) with no transition based on age within the 11 to 25 age group and a structured evaluation to track outcomes over the period of the study. Conclusions Service transformation that is likely to achieve substantial change involves very detailed and carefully orchestrated processes guided by a set of values, principles, clear objectives, training and evaluation. The evidence gathered from this project can form the basis for scaling up youth mental health services in Canada across a variety of environments.