Study design

This was a validation study of a measurement tool comprising two online surveys. The first survey (Survey 1) was conducted in February 2018 and the second survey (Survey 2) was conducted in February 2019. Survey 1 was consisted of a baseline survey and a two-week follow-up to explore the initial factor structure, item characteristics, internal consistency, test-retest reliability, and convergent/known-groups validity. Survey 2 was conducted to collect additional participants to confirm cross-validity for the factor structure by confirmatory factor analysis (CFA). The study protocol was approved by the ethics committee of the Graduate School of Medicine and the Faculty of Medicine, The University of Tokyo (No. 11242-(4)). This article was written according to the standard of development of measurement, Consensus-based Standards for the Selection of Health Measurement Instruments (COSMIN)³¹⁾. The properties of the measurement (i.e., reliability and validity) were reported according to the COSMIN Risk-of-Bias checklist³¹⁾.