In 2017 , 1628 students were randomly selected; 41 of these students refused to answer the questionnaire. In 2018 , out of the 1587 students who answered the questionnaire during T1, 138 changed schools, cities, or school time periods or dropped out of school, and 56 were not present during three consecutive visits. Therefore, the results of 1393 adolescents interviewed during T1 were analyzed during T2 .
Of all participants, the one-year prevalence was 38.4%, meaning that adolescents reported TSP during T1 and T2 . In addition, 155 adolescents who reported TSP at T1 did not report TSP at T2. The one-year incidence was 10.1%; i.e., they did not report TSP during T1, and they were referred as new cases of TSP .
After performing multivariate logistic regression comparing no TSP during either T1 or T2 with TSP only during T2 , the following variables remained risk factors for TSP: adolescent female sex was the only variable that remained in the model and was used as a potential covariate for the adjusted analysis in the second level.
In the present study, TSP was significantly associated with adolescent females aged 15 to 18 years over those aged 14 years or younger.
During this study, 38.4% of the adolescents reported ongoing TSP, and 10.1% reported new episodes of TSP. Epidemiological data, especially on TSP incidence in the general population, are extremely limited. Some data on TSP prevalence have been reported in other countries such as Australia [