BACKGROUND: Children and young people with experience of being in care (e.g. foster care, kinship care, residential care or at home with a supervision requirement order) are at higher risk of adverse mental health and well-being outcomes compared to the general population. Despite a range of policy recommendations and interventions, it is not clear what approaches are effective in the United Kingdom, or how context factors give rise to facilitators and inhibitors of implementation and acceptability.

OBJECTIVES: The CHIMES review is a complex-systems-informed mixed-method systematic review that aimed to synthesise the international evidence base for interventions addressing the mental health and well-being of care-experienced children and young people (age ≤ 25 years) and to assess the potential transportability of this evidence base to the United Kingdom context.

DATA SOURCES: We searched 16 electronic bibliographic databases and 22 websites from 1990 to May 2022. We conducted citation tracking, screened relevant systematic reviews and contacted international experts.

METHOD: We used a convergent synthesis design. We first constructed an evidence map to confirm review scope before undertaking method-level syntheses for outcome evaluations, process evaluations and economic evaluations. These elements were integrated into a review-level synthesis to identify potential evidence-based interventions that may progress to further development, adaptation and evaluation in the United Kingdom. We conducted stakeholder consultations to prioritise intervention theories, types and outcomes.

RESULTS: We identified 64 interventions from 124 study reports. Interventions were primarily evaluated in the United States and targeted young people's competencies or carers' parenting practices. Meta-analysis reported limited evidence that interventions effectively improved mental health in the shorter term (0-6 months): total social, emotional and behavioural problems (d = -0.15, 95% confidence interval -0.28 to -0.02); internalising problem behaviours (d = -0.35, 95% confidence interval -0.61 to -0.08); externalising problem behaviours (d = -0.30, 95% confidence interval -0.53 to -0.08); depression and anxiety (d = -0.26, 95% confidence interval -0.40 to -0.13) and social-emotional functioning difficulties (d = -0.18, 95% confidence interval -0.31 to -0.05), but these impacts were not observed in the longer term (> 6 months). Five key context factors potentially explain challenges to implementation and acceptability: lack of system resources; the time, cognitive and emotional burden of delivery or participation; interprofessional tensions; the devaluing of young people, meaning that they felt unable to express dissatisfaction with interventions; and the devaluating of carers' expertise and needs. From the evidence, stakeholder consultation identified two priority interventions: (1) mentoring by individuals with knowledge and experience of care and (2) system and ethos change to create harmonisation between organisations and facilitate interprofessional relationships. Well-being and suicide-related behaviours are priority outcomes alongside mental health.

LIMITATIONS: The review was limited by a paucity of theory and economic evaluations, so it is unclear how interventions might function or their potential cost-effectiveness. Interventions were insufficiently described, making it challenging to map the evidence base. Outcome evaluations were poorly reported. Due to ongoing restrictions with COVID-19, stakeholder consultations were conducted later than intended with a smaller number of attendees.

CONCLUSIONS: The review identified some evidence for interventions impacting mental health in the short term. There is a lack of system-level interventions and approaches that target subjective well-being and suicide-related outcomes. Future intervention might prioritise mentoring and targeting system culture.

STUDY REGISTRATION: This study is registered as PROSPERO CRD42020177478.

FUNDING: This award was funded by the National Institute for Health and Care Research (NIHR) Public Health Research programme (NIHR award ref: NIHR129113) and is published in full in Public Health Research; Vol. 12, No. 14. See the NIHR Funding and Awards website for further award information.