People experience a wide range of outcomes following a traumatic event. Although rates differ depending on type of trauma, 20-60% of trauma victims may develop posttraumatic stress disorder (PTSD). However, not all trauma victims develop PTSD. Previous research has found that trauma victims who develop PTSD excrete lower levels of urinary cortisol immediately after a trauma than victims who do not develop PTSD. Other research has suggested that increasing levels of cortisol may protect against the development of PTSD in patients such as yourself- but this has not yet been examined. Cortisol is a naturally occurring hormone in your body, and the present study is designed to test whether increasing cortisol levels can protect against or decrease symptoms of PTSD. Participants in this study will be randomly assigned to one of two treatment groups. Participants will receive either hydrocortisone (20mg, twice per day) or a placebo (a sugar pill) for 10 days with a six-day taper. There is an equal chance of being in either treatment group, and neither the participant nor the experimenters will know which treatment was received (except in case of an emergency).