2.1. Design
The ME-WE psychosocial intervention was designed as a cluster-randomised controlled trial (C-RCT) design, with a two (arm) by three (times) repeated measures factorial design [Clusters consisted of AYCs attending the same school (in Slovenia, Sweden and Switzerland) or living in the same geographical area (e.g., neighbourhood) (in Italy, the Netherlands and the UK). Clusters were randomised to the ME-WE intervention or wait-list control arm using an online number generator. To achieve a certain degree of blinding, AYCs were informed that the study aimed to investigate the effects of different support strategies on AYCs’ well-being and were not offered detailed information about the respective other trial arm during the study.Outcomes were measured at the individual level. Primary outcomes were psychological flexibility; mindfulness skills; resilience; subjective mental and physical health; quality of life; impact of caring; and social support. Secondary outcomes were self-reported school, training or work experience performance and attendance. Control variables included caring activities, overall amount of caring and likes and dislikes of caring. The outcomes for the ME-WE intervention arm were compared with the wait-list control arm from the baseline (pre-intervention) through post-intervention and 3-month follow-up (3MFU). After the 3MFU, participants in the wait-list control arm were offered the same programme as the intervention arm.The ME-WE C-RCT was registered as a trial in 2019 (ClinicalTrials.gov Identifier: NCT04114864).More details on the intervention design are described elsewhere [