Students Attending A Random Sample Of Schools Serving Grades 7-12
Participants were consisted of all eligible students attending a random sample of schools serving grades 7-12 in Guangdong province, China. Our samples were selected using a multistage random sampling of public and private junior high schools, senior high schools, and vocational schools. In the first stage we included all of the 21 administrative regions in Guangdong province, China. In the second stage, all schools serving students in grades 7-12 in each administrative region were stratified by type of school (junior high school, high school and vocational school) and academic performance (key school and regular school), then 7-12 schools were randomly selected from created stratas in each region. A total of 291 schools were finally selected in our study. In each selected school, we randomly selected two classes in each grade. Original data were collected from N=83,276 students (reached sample N=104,760, response rate 80%) with a mean age of 16.6 years, between September 2011 and January 2012.
The study protocol was reviewed and approved by the ethics committees of Sun Yat-sen University. The principals of the schools attended by the participants also reviewed and approved the study procedure. Oral informed consent was obtained from each participant.
As mentioned earlier, we specifically chose six psychosocial problems as syndemic indicators including depression, bully, family structure, low SES, academic failure, and school…