Randomization
Randomization with concealed treatment allocation was carried out by a project member not involved in the enrolment or assessments. A web-based randomization facility within CASTOR EDC was used, with a computer-generated randomization scheme and stratification for treatment centre and initial treatment condition in the first RCT, and using random variable block sizes (range 2–6). The outcome of the randomization was reported to the therapist by the research psychologist.The study was approved by the Medical Ethical Review Committee, Amsterdam University Medical Centres, location Free University (registration no. 2017.538, NL62622.029.17), and by the local ethical committees of the participating hospitals and rehabilitation centres. The study was registered in the Dutch Trial Register (NTR6966). The study protocol has been published.