Nearly 70 percent of Americans will be exposed to a traumatic event in their lifetime, and an estimated 20 percent of those will develop post-traumatic stress disorder, or PTSD, according to the PTSD Alliance.
Such traumas could include combat, sexual or physical abuse, a terrorist attack, a serious accident or a natural disaster, according to the U.S. Department of Veterans Affairs National Center for PTSD.
Developing PTSD depends on many factors, including the intensity and length of the trauma, if someone close was killed or injured, how near one was to the event, the intensity of the person's reaction, how much control the person had of events, and how much support the person received after the event.
Symptoms of PTSD -- such as anxiety, feeling "on edge," feeling numb or avoidance behaviors -- disrupt life and make it hard to continue with daily activities, the National Center for PTSD reports.
The National Center identifies four types of PTSD symptoms:
Reliving the event. Intense memories of the trauma return in the form of nightmares or flashbacks, triggering the original feelings of fear and horror.
Avoiding situations that are reminders of the event. Some people actively avoid situations or people that trigger memories of the trauma. They stay very busy and do not seek help.
Feeling numb. PTSD sufferers can have difficulty expressing feelings, cultivating relationships, enjoying activities previously liked, or even remembering the trauma itself.
Feeling keyed up. People with PTSD may feel jittery or as though they are always on the lookout for danger. They may be angry or irritable or have trouble concentrating or sleeping.
More information is available at www.ptsd.va.gov.