Optimal transition  is a multidimensional, multidisciplinary, lengthy process continuing on into adult care, marked by joint responsibilities in multidisciplinary working.
Young people undergoing transition are also negotiating a developmental transition from childhood to adulthood, which generates needs  beyond those which are illness-specific.
In recent years, transitional care has become an important focus for both policy and practice across health care systems, since problems which arise at interface are not specialty or disorder specific, but embody common challenges for paediatric and adult services.
An equally important influence on service culture and structure in the last decade has been the changing experience of developmental transition.  
In the next 10 years, mental health problems are expected to increase among children and youth, with current predictions estimating at least 50% increase in incidence rates.
Intervening at the level of the transition represents one of the most important ways that we can facilitate not only recovery but also mental health promotion and mental illness prevention. It also has the potential for enormous cost savings .