Table 1 PICOS inclusion criteria

P: Population

The service’s key target group is those aged under 18

‘Common mental health problems’ agreed by the study advisory group to be: anxiety and related disorders; depression; self-harm; PTSD; emerging personality disorder; adjustment disorder; ADHD/ADD; conduct disorder; oppositional defiant disorder; substance misuse disorders; ‘at risk of psychosis’

Note: the funding body’s call for research proposals specifically excluded psychosis, eating disorders and autism spectrum disorders because other research projects in their portfolio were investigating these conditions

I: Intervention

Any service provided for CYP experiencing common mental health problems

C: Comparators

Not applicable

Effectiveness/cost-effectiveness studies only: alternative service models, standard care, treatment as usual or inpatient/residential care

O: Outcomes

Not applicable

Effectiveness studies: relevant measures of CYP’s mental health, family functioning, educational attainment or quality of life

Cost-effectiveness studies: incremental cost-effectiveness of service model vs. comparator

Acceptability studies: qualitative and quantitative data capturing stakeholder views

S: Study design (document type)

Any document containing a sufficiently detailed description of a relevant service

Peer-reviewed empirical studies

Effectiveness studies: at least one pre/post relevant outcome measure reported

Cost-effectiveness studies: costs, health outcomes or incremental cost-effectiveness analyses reported

Acceptability studies: data that directly or indirectly reflected participants’ views of, or participation in, the service reported