This observational study follows subjects who have been exposed to a traumatic event and are at risk of developing PTSD symptoms. Participants are recruited within six hours of a traumatic event, and, starting from the recruitment session, are then examined on six set points of time within a period of thirteen months. The examinations include both biological studies of cortisol in hair, blood and saliva, and psychological examinations and questionaires that assess the development and severity of PTSD symptoms.

The novel method of sampling hair cortisol allows investigators to retroactively estimate the mean levels of blood cortisol during the tree months prior to the sampling.

The study aims at further illuminating the correlation between cortisol levels both prior and following a traumatic event, and the development and severity of PTSD symptoms

Inclusion Criteria:

• Age 18-70.
• Experienced a traumatic and were at risk (or perceived risk) of serious injury to themselves or others in their surroundings.
• Signed an informed consent form.

Exclusion Criteria:

• Age under 18 or over 70.
• Severe or complex physical injury, such as severe head trauma, massive burns or injuries that require surgery under full anesthesia.
• A personal history of Psychotic state or PTSD.
• Pregnancy
• Weight below 45 Kg or over 120 Kg.
• Hair shorter than 1.5 cm.

Men and women, age 18-70, who were examined in the ER following a traumatic event.