This study is designed to test the effect of an explanation about the first sleep following trauma exposure, on the development of Post Traumatic Stress Disorder (PTSD) in the months following the traumatic event.

This is a Single blind, prospective, placebo controlled trial in which trauma victims are randomized to receive an explanation about the first sleep following trauma exposure.

To provide a baseline prior the explanation, participants will receive a medical and psychological evaluation. at this point the participants will be given one of two explanations about sleep. The experimental group will receive an encouragement to deprived sleep explanation, and the control group will receive an encouragement to sleep explanation, Lorazepam 1mg will be offered to assist sleep. 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 months. Further assessments might be done at 6 & 13 months.

Eligible subjects will include men and women age 18-70, 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.

Potential participants will be recruited from trauma victims who arrived at the Chaim Sheba Medical Center Emergency Room.

Inclusion Criteria:

1. Persons age 18-70, who have been exposed to an event meeting the DSM-IV "A.1" criterion for trauma exposure.
2. Persons who arrived at the Chaim Sheba Medical Center Emergency Room.
3. Who 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 clinical judgment;
2. Traumatic exposure that reflects ongoing victimization (e.g., domestic violence) to which the subject is likely to be re-exposed during the study period.
3. Overt psychopathology, intoxication, or under the influence of substances.
4. Evidence or history of schizophrenia, bipolar, other psychotic condition;
5. Prior history of PTSD;
6. Current or past history of dementia, amnesia, or other cognitive disorder predating trauma exposure;
7. Assessed serious suicide risk. -