The purpose of this study is to determine whether a computerized training, "Cognitive Bias Modification" targetting appraisals (CBM-App), can reduce dysfunctional appraisals of trauma in patients with Post-Traumatic Stress Disorder (PTSD), compared to a control condition. Other outcomes measured include symptoms of PTSD and trauma-relevant dysfunctional cognitions. Participants are recruited from inpatients with PTSD admitted to the Clinic for Psychosomatic Medicine and Psychotherapy, LWL University Clinic of Ruhr University of Bochum.