A post-traumatic Stress Disorder (PTSD) is the one disorder discussed in this chapter that is necessarily associated with trauma. The traumatic event must involve actual or threatened death or serious physical injury to the patient or others and must elicit a response of intense fear, horror, or helplessness on the part of the patient. The PTSD has multiple dimensions that entail cognitive, behavioral, emotional, and vegetative disturbances. Dr. Khatib was concerned that the dizziness and difficulty concentrating, while they might be due to anxiety over the severe traumas Paula experienced, could also have been caused by blows to her head. Dr. Frank assured Paula that her symptoms of poor sleeping, distracting thoughts, being easily startled, and feeling socially ill at ease were normal for someone who had been through events like those she experienced. One of the matters of extreme interest to a biologist that becomes especially relevant in Paula's case relates to sex differences and PTSD.