This study investigated the psychiatric effects of acute psychological trauma. Over three years, the study recruited and assessed 275 patients, aged 16 and 65 years, arriving at the Hadassah University Hospital emergency room in Jerusalem, Israel, after a traumatic event. Participants were followed up at one week, one month, and four months after the traumatic event. A subgroup of participants with PTSD at four months was assessed again one year after the traumatic event.