ObjectiveTo investigate the depressive disorder of middle school students and find out factors influencing the incidence of depressive disorder.MethodsA self-designed demographic questionnaire, Strengths and Difficulties Questionnaire (SDQ), and Kutcher adolescent depression scale (KADS) were used. Children who reached the total difficulty score of SDQ and the delimitation score of KADS were selected and the mini international neuropsychiatric interview for children and adolescents (MINI-KID) was performed.ResultsA total of 7 978 students were enrolled. KADS scores of boys were higher than those of girls (P<0.01). The total score of KADS increased with the grade. The total score of KADS of grade 2 students in senior high school was the highest and that of grade 1 students in junior high school was the lowest (P<0.01). Logistic regression analysis showed that the risk factors of depressive disorder were old age, old maternal childbearing age, high self-value, more emotional problems, scatterbrain, and poor relationship with peers.ConclusionDepressive symptoms of boys are severer than those of girls and aggravate with the grade. The influencing factors of depressive disorder are age, maternal childbearing age, self-value, emotional problems, scatterbrain, and relationship with peers.