Abstract
The transition from Child and Adolescent (CAMHS) to Adult Mental Health Services (AMHS) can be challenging. Drawing on the sample of the European MILESTONE project, we explored changes in clinical profiles and treatment outcomes in adolescents transitioning to AMHS over two years, focusing on different pharmacological treatment patterns. The sample (N = 690; mean age: 17.7 years; SD = 0.29) was categorised into three groups based on medication patterns: continuous (Group 1), intermittent (Group 2), and never medicated (Group 3). Participants underwent four evaluations over two years using tools measuring psychopathology and functioning, including the Health of the Nation Outcome Scale for Child and Adolescents (HoNOSCA) and ASEBA Battery. We employed repeated-measures models to analyse clinical rating changes and a two-way mixed ANOVA to assess interaction between time and groups. Group 3 had significantly lower mean HoNOSCA ratings than Groups 1 and 2 (p < 0.001), indicating better mental health. By the last time point (T4), the factors associated with a reduced risk of severe illness included an improvement in the risk of suicide attempts (p = 0.038), enhanced everyday functional skills (p = 0.008), higher quality of life (p = 0.001), and being male (p = 0.020). The ASEBA Battery showed Group 1 had more internalising symptoms, while Group 2 had more externalising symptoms than Group 3. During the transition from CAMHS to AMHS, continuous medication was associated with higher symptom severity than intermittent or no pharmacological treatment. This may reflect either a more severe initial symptomatology requiring sustained pharmacotherapy or a medication-related paradox, whereby symptoms persist or intensify owing to treatment resistance or side effects. TRIAL REGISTRATION: "MILESTONE study" registration: ISRCTN ISRCTN83240263 Registered 23 July 2015; ClinicalTrials.gov NCT03013595 Registered 6 January 2017.