Trial design
The reporting of this study follows the CONSORT-SPI 2018 guidelines for social and psychological interventions with cluster extensionThis trial was preregistered at the Dutch Trial Register (04/03/2019, Trial NL7562), approved by the local ethics committee (Vaste Commissie Wetenschap en Ethiek; VCWE-S-18-00149) and conducted in accordance with the Declaration of Helsinki. We made a few unforeseen changes following trial commencement. The COVID-19 pandemic started in between T2 and T3. We added two new questionnaires (T3) with the aim to investigate the relation between mindset and resilience during COVID-19, and the mediating role of coping mechanisms: brief Cope