BackgroundThe purpose of this study was to examine post-traumatic stress, depression, anxiety, and complicated grief in Korean high school students who experienced a peer suicide.MethodsA total of 956 students were included in the statistical analysis. One week after a peer suicide, a school-based crisis intervention program was conducted. The cohort was followed-up at one week and five months after a peer suicide. The program consists of screening tests, educational sessions, and further interview with psychiatric specialists for the selected group. Screening tests were conducted for all students to measure the Child Report of Post-traumatic Symptoms (CROPS), the post-traumatic stress symptoms (The University of California at Los Angeles post-traumatic stress disorder [PTSD] reaction index; UCLA-PTSD-RI), the anxiety symptoms (The Korean-Beck Anxiety Inventory; K-BAI), the depressive symptoms (The Korean-Beck Depression Inventory-II; K-BDI-II), and the complicated grief reaction (The Inventory of Complicated Grief; ICG). For statistical analysis, the SPSS Statistics 21.0 program was used.ResultsAt baseline and five months follow-ups, 8.6% and 2.9% of the students showed post-traumatic stress symptoms. At five months follow-up, there was a statistically significant decline in the post-traumatic stress symptoms, anxiety, depression, and complicated grief among the ‘trauma group.’ A higher proportion of the female students showed post-traumatic stress symptoms after the incident of peer suicide than the male students.ConclusionSchool-based crisis intervention helps improvement of trauma-related symptoms. It might be an effective way to prevent suicide spreading among students by alleviating trauma-related symptoms.