H school students recruited from six cities in the Guangdong Province
H school students recruited from six cities inside the Guangdong Province through a threestage stratified group sampling method. For the very first stage, the cities have been divided into 3 strata based on their economic level, and two cities were chosen in every stratum. For the second stage, 2 schools (six junior higher schools, 4 senior higher schools and 2 vocational high schools) were randomly selected from all of the schools in each city. For the third stage, 2 classes have been randomly chosen from every grade within the chosen 
schools. All students (a total of 25,655) within the chosen classes had been asked to take part in this study and provided informed consent voluntarily. A total of 23,877 valid questionnaires had been collected, resulting in a valid rate of 93.36 .Data CollectionTo shield the privacy from the students, anonymous questionnaires have been MedChemExpress F16 administered by trained interviewers within the absence with the teachers (to prevent any prospective info bias). The students were essential to fill out the questionnaires for the duration of class time.Ethical StatementThis study received approval in the Sun YatSen University, School of Public Overall health Institutional Assessment Board. All participants have been totally informed on the goal of the study and have been invited to participate voluntarily. Written consents had been obtained from every participant and their parents.MeasuresDemographic traits. The demographic questionnaire elicited details on age, gender, grade, economic status, academic pressure, relationships with families, classmates and teachers, and smoking. Family financial status was measured by asking the student’s perception of their family’s current status (rated from good to poor). Academic pressure was captured by a single item based on the student’s selfrating from low to higher. Relationships with families, classmates and teachers have been assessed primarily based around the student’s selfrating from great to poor. Smoking was assessed by asking, “Did you smoke at the least a single cigarette per week” Sleep top quality. The students’ sleep good quality was measured by the Chinese version of PSQI, which consists of 9 things producing 7 components: subjective sleep high quality; sleep latency; sleepPLOS One particular DOI:0.37journal.pone.02602 March 26,3 Bullying as a Threat for Poor Sleep Qualityduration; habitual sleep efficiency; sleep disturbances; use of sleep medication; and daytime dysfunction. The CPSQI had been proven to have a good general reliability and testretest reliability. The CPSQI has a cutoff value of 7, with larger international scores indicating poorer sleep top quality [24]. Bullying behaviors. You will find 4 profiles connected with bullying: pure bullies (students who bully and are never victims), pure victims (students who’re victims of bullying and under no circumstances attack others), bullyvictims (students that are both victims of bullying and who bully other people) and neutral (students in no way involved in bullying). The inquiries about bullying and victimization consisted of 2 parts, using the answers given on a 3point scale as follows: under no circumstances, 2sometimes (one or two occasions) or 3often (greater than three times). Students reporting no less than a single bullying behavior using a frequency of “often” previously 30 days have been classified as bullies [26]. Victims have been people who reported a minimum of a single victimization experience in the past 30 days having a frequency of “often.” Bullyvictims met the criteria for becoming each a bully and also a victim. All other students had been labeled PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/24134149 as neutral [27]. Bullying questionnaire. The questions about bul.