This study is designed to test the hypothesis that a single administration of intranasal oxytocin within 6 hours post-trauma facilitates the physiological recovery for the trauma, thereby preventing the development of Post Traumatic Stress Disorder (PTSD) in the months following the event. In the absence of such treatment (i.e., under placebo conditions), we hypothesize that a greater proportion of persons will develop PTSD (i.e., fail to recover from acute effects).

This is a double-blind, placebo-controlled trial in which trauma victims are randomized to receive a single intranasal administration of either Oxytocin (40IU) or placebo within the first six hours following trauma exposure. To provide a pre-treatment baseline, participants will receive a medical and psychological evaluation prior to treatment. After two weeks the research assistant or study psychiatrist will perform behavioral ratings and complete history details pertaining to PTSD risk factors. Participants will be assessed again by the study psychiatrist or research assistants at 1, 3, 6 and 13 months. Eligible subjects will include men and women over the age of 18, who have been exposed to an event meeting the DSM-IV "A.1" criterion for trauma exposure, and who provide written, informed consent to participate in the study. In order to recruit persons who are more likely to be at risk for the development of PTSD, we will only randomize persons expressing marked anxiety, emotional distress or dissociation, as assessed by the Visual Analog Scales. Potential participants will be recruited from trauma victims arriving at the Chaim Sheba Medical Center Emergency Room.

Inclusion Criteria:

1. Persons over the age of 18, who have been exposed to an event meeting the DSM-IV "A.1" criterion for trauma exposure, expressing marked anxiety, and/ or emotional distress and/or dissociation, as assessed by the Visual Analog Scales
2. The traumatic event occured up to six hour prior to the arrival to the emergency room
3. The person can and is willing to provide written, informed consent to participate in the study.

Exclusion Criteria:

1. Physical injury that would contraindicate participation or interfere with a subject's ability to give informed consent or cooperate with the screening or collection of initial measures. Examples include severe burn injury, life-threatening medical or surgical condition, condition requiring surgical intervention under general anesthesia, as indicated by Abbreviated Injury Scale (AIS), or by clinical judgment;
2. Head injury involving confusion, loss of consciousness, or amnesia;
3. Medical conditions in which oxytocin administration might cause harm to the patient such as patients with a cardiovascular disease or intracranial mass.
4. Weight below 45 or above 100 kg.
5. Pregnancy (in suggestive cases, a pregnancy test will be performed);
6. Traumatic exposure that reflects ongoing victimization (e.g., domestic violence) to which the subject is likely to be re-exposed during the study period.
7. Overt psychopathology, intoxication, or under the influence of substances.
8. Evidence or history of schizophrenia, bipolar, other psychotic condition, autism;
9. Prior history of PTSD;
10. Current or past history of dementia, amnesia, or other cognitive disorder predating trauma exposure;
11. Assessed serious suicide risk.