48 Supplementary Material Reviewer comments: Click here to view.(6.9K, pdf) Acknowledgments The authors thank Susie Bernier for the translation and Isabelle

Gaumond for the final revision of the manuscript. Footnotes Contributors: concerning CH, M-CC and MC initiated the project and designed the study. AB (implementation analysis), EMC (health literacy), M-FD (statistical analysis), MF (multimorbidity), TF (case management), CL (poverty), JM (healthcare database), PP (participatory research), PR (mental healthcare) and CR (case study) provided specific expertise. All authors contributed to the redaction and approved the final version of the manuscript. Funding: This work is supported by the Canadian Institutes of Health Research (CIHR) grant number 318771. Competing interests: None. Ethics approval: The research protocol was approved by the Ethics Research Boards of the four HSSCs involved (Chicoutimi, Jonquière, Alma and La Baie). Provenance and peer review: Not commissioned; internally peer reviewed.
Attention deficit/hyperactivity disorder (ADHD) is the most common neurodevelopmental disorder and affects 3–5% of children and young people.1 The core symptoms of ADHD include poor attention,

hyperactivity and impulsivity. National Institute for Health and Care Excellence (NICE)1 guidelines provide a blueprint for the diagnosis and management of ADHD in England and Wales and indicate the need for young people with ADHD to have access to the best evidence-based care in order to fulfil their potential and prevent poor outcome. However, in practice, delivery and quality of care is ad hoc, with little consistency in assessment,

diagnosis or management.2 ADHD frequently coexists with other neurodevelopmental and psychiatric disorders and is a risk factor for major educational, social and occupational impairment, placing a huge burden on the National Health Service (NHS), social care and criminal justice systems. There has been a rapid growth in diagnosis over the past 30 years with the number of children recognised and treated for ADHD in the UK increasing almost 10-fold from the early 1980s1 and spending Entinostat on medication for ADHD increasing sevenfold between 1998 and 2005.3 The cost of initial specialist assessment for ADHD is estimated at £23 million annually in England and Wales4 and drug costs for ADHD in England during 2012 was expected to exceed £78 million3 while indirect costs to families include parental mental ill health, time off work and loss of earnings are even higher.5 Increasing recognition of ADHD as a lifespan condition is placing a new demand on the NHS to provide diagnostic and treatment services for children, adolescents and adults, exposing serious limitations in existing methods of assessment and management. There is no single test, or biomarker used to diagnose the disorder.