Group-Delivered guided written exposure therapy (GWE) is a manualized exposure-based therapy program consisting of 5-8 sequential sessions. The interval between every 2 consecutive sessions is 0-2 days. There will be 5-8 group-delivered sessions in total (only one index trauma will be discussed), and 1-2 weeks to complete.The first and last sessions are scheduled to last for 1.5 hours each, while the other sessions will be 50 minutes in duration.

PCL-5 was a 20-item self-report scale that assesses PTSD DSM-5 diagnosis and symptom severity in the past month. Items were rated on a 5-point Likert scale from 0 ("not at all") to 4("extremely").The Chinese version of PCL-5 has shown good psychometric properties in trauma-affected Chinese adolescents.

CPTSD symptoms include two parts: PTSD symptoms were assessed using six PCL-5 items mapped to ICD-11 domains: re-experiencing (items 2 and 3), avoidance (items 6 and 7), and sense of current threat (items 17 and 18). Disturbances in self-organization (DSO) were measured using the 6-item DSO subscale of the International Trauma Questionnaire-Child and Adolescent Version (ITQ-CA), which has demonstrated good validity in Chinese adolescent samples. The resulting 12-item composite yielded total scores ranging from 0 to 48, consistent with ITQ-CA scoring conventions.

Patient Health Questionnaire 9-item (PHQ-9), a self-report measure for depressive symptoms in past two weeks, comprises 9 items rated from 0 (not at all) to 3 (nearly every day). The PHQ-9 has good psychometric properties in Chinese adolescents.