We thank Dr Ian Stepheson for his invaluable advice and experience in constructing the questionnaires and generous support from the chiefs of service in the participating departments. We also thank Ms Kate TC Ng for organising the questionnaire administration. Contributors: JSY Chor and PKS Chan designed the study, interpreted the findings, and wrote the manuscript; KLK Ngai collated the survey data; WB Goggins and SYS Wong performed statistical analyses; MCS Wong, N Lee, TF Leung, TH Rainer administered the survey; S Griffiths supervised the study. All authors, external and internal, had full access to all of the data (including statistical reports and tables) in the study and can take responsibility for the integrity of the data and the accuracy of the data analysis. Funding: This study did not receive any external funding. Competing interests: None declared. Ethical approval: The study was approved by the Survey and Behavioural Research Ethics Committee of the Chinese University of Hong Kong. Data sharing: no additional data available.