This is a randomized controlled study comparing telephone-based cognitive behavioral therapy (CBT) for recent survivors of traumatic events with Acute Stress Disorder (ASD) or acute PTSD with a waitlist control group. Survivors with PTSD from both groups will receive face-to-face CBT one month from the traumatic event. The study's main hypothesis is that early telephone-based CBT will reduce the prevalence of PTSD three and eight months after the traumatic event.

Post-traumatic Stress Disorder (PTSD) is a prevalent and pervasive mental disorder. Studies have shown that there is a significant reluctance to use mental health services by trauma-exposed individuals at high risk for developing PTSD. Providing clinical services in combat or disaster zone might be difficult. Trauma-focused cognitive behavioral therapy (CBT) effectively reduces the prevalence of PTSD among recent survivors. Telephone based CBT was found to be effective in mood and anxiety disorders, but has not been tried in PTSD. Establishing the effectiveness of telephone based CBT has significant service delivery and public health implications. Preventing PTSD significantly reduces individuals' suffering and disability We will screen, by telephone, up to 1200 survivors of traumatic events, from a general hospital emergency department trauma registry list, randomize the first 240 with ASD or Acute PTSD to either early, telephone based cognitive behavioral therapy (ET_CBT) (n=120) or a no-treatment control condition (n=120). We will provide five sessions of ET-CBT to the former and compare the two groups three and eight months later.

Survivors from both groups who will continue to have PTSD at three months (after either treatment or waiting list), will receive 12 sessions of face-to-face, trauma focused CBT. A first phase of the study will consist of establishing the acceptance of ET-CBT and its main components (e.g., exposure to traumatic reminders) by survivors, and optimizing the protocol. It will involve 20 survivors and no randomization. Subsequent to that phase we will start recruiting for the main study. The study's main hypothesis is that early CBT will reduce the prevalence of PTSD three and eight months after the traumatic event.

Inclusion Criteria:

• Adults
• Exposure to psychologically traumatic events
• Diagnosis of Acute Stress Disorder or Post-traumatic Stress Disorder
• Up to four weeks after trauma exposure

Exclusion Criteria:

• Chronic PTSD
• Past and present psychosis, bipolar disorder, opiate or stimulants use
• Medical or surgical condition that interfere with subjects ability to participate in the study or sign an informed consent
• Lack of fluency in the study's main language (Hebrew)

Recent trauma survivors recruited following admission to a general hospital emergency room following traumatic events. Consecutive survivors screened and enrolled if eligible