Community mental health treatment and subsequent outcomes in children and young people: what works, for whom, and why?

The sequelae of children and young people's (hereafter: CYP) mental disorders are broad and long-lasting.1,2 Despite pledges to increase mental health funding in the UK,3 CYP experience difficulties accessing services and long wait times.4 Since the start of the COVID-19 pandemic, population studies suggest that CYP's mental health deteriorated,5-8 with a 53% increase in contacts made to CYP's mental health services (MHS) in England compared to before the pandemic.9 Given rising demands, it is crucial that MHS for CYP are optimised. There is a paucity of information regarding effectiveness of treatment-as-usual MHS in CYP, with uncertainties regarding which individuals improve, and whether similar outcomes would be seen without treatment.10 This proposal aims to: - assess the effectiveness of community MHS on CYP's mental health and functioning compared with those who do not to access treatment; - better understand which MHS contacts are helpful for whom (moderation) and why (mediation); - determine whether prior contact with MHS protect CYP against pandemic-related impairments and under what circumstances. Findings will inform clinicians and policy makers of how to optimise the effectiveness of MHS, and to improve commissioning and delivery to better meet the needs of CYP.