Recruitment potential per center, difficulties and study adaptations
RECRUITMENT, RECRUITMENT
In Heidelberg, 55 individuals were screened within 36 months of recruitment. Of those, eight did not fulfill participation criteria. Of 47 individuals potentially eligible, 29 (62%) were recruited for study participation. The mean overall recruitment rate per month was 0.9. Yet, monthly recruitment rates increased over the course of the study: During the first 24 months, 14 adolescents were recruited, i.e., recruitment rate was around 0.6 per month. At the time, parts of the diagnostic appointments were located in the child and youth psychiatry and part of it in the institute where the study was conducted. As a result, concurring studies were offered at the child and youth psychiatry, and changes in personnel and location seemed to confuse prospective participants. Moreover, participants recruited by the study institute reported reservations towards the child and youth psychiatry; and those recruited by the child and youth psychiatry reported reservations towards the study program as it was unfamiliar. Recruitment rates were lower than necessary for successful implementation of the RCT design. Consequently, the design was changed into a single-arm feasibility study, diagnostic appointments did not any longer include visits to the child and youth psychiatry and recruitment was stimulated again. In the third and last recruitment year in Heidelberg, 15 adolescents were recruited, i.e., the recruitment rate was doubled to around 1.3 per month.In Mainz, 31 adolescents were screened within 16 months of recruitment. Of those, three adolescents did not fulfill participation criteria. Of 28 individuals potentially eligible for study participation, 16 (57%) were recruited for participation. The mean overall recruitment rate per month was one. Therapies in Mainz were conducted in the outpatient department of the child and adolescent psychiatry, so that in contrast to the Heidelberg study center, recruitment numbers likely benefitted from close connection to the child and adolescent psychiatry. Notably, eleven of the 16 recruited adolescents were included in the first seven months of recruitment from September 2019 to March 2020 up until the beginning of the first wave of the COVID-19-pandemic. In the last five months of recruitment from August to December 2020, five more adolescents were recruited, while from April to July 2020 none were included into the study. Thus, the number of potential participants in Mainz was likely reduced by the start of the pandemic in the middle of the recruitment phase.