1 University of Macau, Faculty of Social Sciences, Department of Psychology, Taipa, Macau, China; Sun Yat-sen Center for Migrant Health Policy, Guangzhou, China. Electronic address: brianhall@umac.mo.
2 Faculty of Medical Statistics and Epidemiology, School of Public Health, Sun Yat-sen University, Guangzhou, China; Sun Yat-sen Center for Migrant Health Policy, Guangzhou, China.
3 Department of Health Behavior and Society and Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
4 Sun Yat-sen Center for Migrant Health Policy, Guangzhou, China; University of North Carolina Chapel Hill Project-China, Guangzhou, China; University of North Carolina Chapel Hill, Institute of Global Health and Infectious Diseases, Chapel Hill, NC, USA.