PTSD is a trauma-related disorder that can develop after a person is in some way exposed to or personally experiences a traumatic event. When a person develops PTSD, they experience recurrent thoughts or memories of the trauma, have nightmares, flashbacks, and become distressed at any reminder of the trauma. People with PTSD go to great lengths to avoid any reminder of the trauma due to the severe distress caused by such memories. They tend to feel sadness, guilt, and shame and withdraw from loved ones and from most social situations. PTSD can cause the affected person to become irritable or aggressive, hypervigilent or paranoid, have difficulty concentrating, and demonstrate chronic sleep disturbance.