Evaluating Symptom Variations and Observing Longitudinal Individual Change Effects in TF-CBT

Participants will be included if: 1. they are between 12 and 18 years of age; 2. they have been exposed to at least one or more traumatic event(s) according to the DSM-5 A criteria after the age of 3 years and dating back at least 1 months (with regard to the ability of patients to remember the event(s) and to the high spontaneous remissions of PTSS in the first month after a traumatic event); 3. they exhibit high severity of DSM-5 PTSS as indicated by a total symptom score of ≥25 assessed with the Child and Adolescent Trauma Screen 2 (CATS-2); 4. a nonoffending adult caregiver is available for the treatment and willing to participate in weekly treatment sessions (the inclusion of a caregiver is integral to the TF-CBT treatment model); 5. they are willing and able to attend weekly treatment sessions; 6. if their living circumstances are safe and stable to minimize the risk of re-traumatization during the project; 7. they and their caregiver have sufficient command of the German language (i.e., to participate in assessment \[read\] and treatment\[converse\]); 8. they and their caregivers possess a smartphone. 9. they and their caregiver provided written informed consent. Participants will not be included if: 1. they exhibit acute suicidal behavior or have suicidal ideations requiring immediate hospitalization; 2. they have a documented developmental disorder (i.e., autism spectrum disorder) or current psychosis based on adolescent- and caregiver-report and clinical assessment; 3. they exhibit severe substance misuse based on clinical assessment; 4. take part in concurrent psychotherapy during TF-CBT; 5. exhibit severe intellectual disability based on clinical assessment.