Disruption of care during transition from child and adolescent mental health (CAMHS) to adult mental health services (AMHS) may adversely affect the health and well-being of service users. Indeed, transition-related discontinuity of care is a major health and societal challenge today. Current evidences show that this transition is not always properly managed and that improving the transition process can have a positive impact on the health and wellbeing of young people. Nevertheless, data available are still inconsistent and only few studies investigated possible models aimed at improving and operationalize the transition. At present, no information concerning the transition in the Geneva Canton is available.

According to this lack of evidence, the current study aims at: 1) mapping the CAMHS/AMHS interface; 2) evaluating the longitudinal course and outcomes of adolescents approaching the transition boundary (TB) of their CAMHS; 3) determining the effectiveness of an experimental model of managed transition in improving outcomes, compared with usual care; 4) comparing these results with those of the EU funded MILESTONE study from several other European countries.

The investigators will recruit all patients aged ≥ 16 years and 6 months from the Geneva Canton in charge at CAMHS and they will follow them for up to 24 months. CAMHS will be instructed to provide all their service users at the time of transition either usual care or a novel service called "Managed Transition", which will include the use of a new decision support tool, the Transition Readiness and Appropriateness Measure (TRAM). A nested cohort Randomised Controlled Trial (ncRCT) design will be applied to divide patients into the two groups. The health and wellbeing of the young people will be assessed at baseline and then followed-up for 24 months to see whether they transition to AMHS or are discharged or referred to some other service. The investigators will then evaluate what impact the different transition experiences have on young people's health and wellbeing, and whether the process of Managed Transition has any benefits as compared to usual care.

Inclusion Criteria:

• 1) provides valid written informed consent, or assent, if below the legal age of consent;
• 2) age is within 18 months of reaching the transition boundary of their CAMHS - during the trial recruitment period;
• 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 standardized 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 18 months before the transition boundary of their CAMHS;
• 3) has intellectual impairment (IQ < 70) as ascertained by standardized assessment or diagnosed by clinician;
• 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.