Given the high rates of violence in many neighborhoods, school officials are becoming more familiar with the phenomenon of post-traumatic stress disorder (PTSD) and its crippling effect on children. The majority of children who either witness or experience violence display symptoms of PTSD and depression. One 10-week, school-based intervention has been shown to significantly lessen many of these effects. Researchers working with the Los Angeles public schools designed a group therapy program for use by school-based mental health clinicians to treat students with clinical levels of PTSD. The program served 126 sixth-graders in two schools in low-income neighborhoods. Psychiatric social workers used cognitive behavioral techniques to get students to remember their trauma, understand their symptoms and develop strategies to prevent relapse. Students' self-reported PTSD symptoms and depression; parental reports and teacher reports all furnished researchers with data for measurements. After three months, students who went through the programs scored significantly lower PTSD symptom measures. Indeed, researchers describe the program's impact on PTSD symptoms as very large. Some potential limitations of this research include the discrepancies between teacher assessments and those of other respondents, as well as the fact that this intervention was administered within a single academic year, rendering any analysis of outcomes strictly short term. Nevertheless, the authors of this study say that their work marks a new contribution in the form of an evidence-based treatment model.