This study evaluates the longitudinal health and social outcomes of adolescent mental health service users who are at the transition boundary of their child and adolescent mental health service, and whether the implementation of a model of managed transition at the service boundary benefits them, as compared to usual care.

The MILESTONE study focuses on the period when young people attending a children and adolescents mental health service (CAMHS) need to move on, or "transition", to an adult mental health service (AMHS), if they still require care or treatment. We know from other research that this transition is not always properly managed and that improving the transition process can have a positive impact on the health and well-being of young people in this position. We want to evaluate what impact the different transition experiences have on young people's health and well-being, and whether the process of Managed Transition has any benefits as compared to usual care.

The MILESTONE study is run in eight European countries (UK, Ireland, Belgium, Holland, France, Germany, Italy and Croatia). CAMHS in the study regions are selected to provide the young people in their care that are reaching transition age either usual care or a novel service called "Managed Transition", which includes the use of a new decision support tool, the Transition Readiness and Appropriateness Measure (TRAM). This should help with decision making and enable better transitions by identifying cases for whom transition from CAMHS to AMHS is advisable and appropriate, or who can be safely discharged or referred to a community based service. CAMHS are randomly assigned to provide the intervention of Managed Transition or usual care. The health and well-being of the young people attending these services is assessed at the start of the study and then followed-up for 24 months to see whether they transition to AMHS or are discharged or referred to some other service.

Inclusion Criteria:

• Young person inclusion:

  1. Provides valid written informed consent, or assent, if below the legal age of consent
  2. If age is within one year of reaching the transition boundary of their CAMHS during the trial recruitment period, and, in exceptional cases, not more than 3 months older than the transition boundary, if a decision about transition has not yet been made
  3. Has a mental disorder defined by DSM-IV-TR, DSM-5 or ICD 10/11, or is under the regular care of CAMHS (if not yet diagnosed)
  4. Has an IQ ≥ 70 as ascertained by previous standardised assessment or diagnosed by clinician, or no indication of intellectual impairment

Exclusion Criteria:

• 1. Does not provide valid written informed consent, or assent, if below the legal age of consent 2. Is younger than a year before the transition boundary of their CAMHS 3. Has intellectual impairment (IQ <70) as ascertained by previous standardised assessment or diagnosed by clinician (if no data on intellectual functioning are available [because it has never been assessed] then care coordinators will be asked to make a clinical judgement on intellectual impairment before baseline assessment takes place) 4. If not able to (or expected not to be able to) complete the questionnaires due to severe physical disabilities or language problems, even with assistance from family members or research assistant 5. Service user in a secure forensic institution