(PTSD) may occur soon after a major trauma, or can be delayed for more than six months after the event. When it occurs soon after the trauma it usually resolves after three months, but some people experience a longer-term form of the condition, which can last for many years.

PTSD can occur at any age and can follow a natural disaster such as flood or fire, or events such as war or imprisonment, assault, domestic abuse, or rape. The terrorist attacks of Sept. 11, 2001, in the U.S. may have caused PTSD in some people who were involved, in people who witnessed the disaster, and in people who lost relatives and friends. These kinds of events produce stress in anyone, but not everyone develops PTSD.

We do not know what causes PTSD, but psychological, genetic, physical, and social factors are involved. PTSD alters the body’s response to stress by affecting stress hormones and neurotransmitters (chemicals that transmit information between our nerves). Previous exposure to trauma may increase the risk, which suggests that this kind of a reaction may be a learned response.

Having good social support helps to protect against developing PTSD. In studies of Vietnam veterans, those with strong support systems were less likely to develop PTSD than those without social support.

People with PTSD re-experience the event again and again in at least one of several ways. They may have recurrent distressing dreams and recollections of the event, a sense of reliving the experience (referred to as flashbacks), and/or become very distressed around the time of events that symbolize the event (such as anniversaries).

Symptoms of PTSD fall into three general categories:

1. Repeated "reliving" of the event, which disturbs day-to-day activity

• Recurrent distressing memories of the event
• Recurrent dreams of the event
• Flashback episodes, where the event seems to be recurring
• Bodily reactions to situations that remind them of the traumatic event

2. Avoidance

• Inability to remember important aspects of the trauma
• Lack of interest in normal activities
• Feelings of detachment
• Sense of having no future
• Emotional "numbing", or feeling as though they don’t care about anything
• Reduced expression of moods
• Staying away from places, people, or objects that remind them of the event

3. Arousal

• Irritability or outbursts of anger
• Sleeping difficulties
• Difficulty concentrating
• Exaggerated response to things that startle them
• Hypervigilance

Other symptoms that may be associated with this disease include a sense of guilt about the event (including "survivor guilt"), and the following symptoms, which are typical of anxiety, stress, and tension:

• Paleness
• Feeling your heart beat in your chest, called palpitations
• Headache
• Fever
• Fainting
• Dizziness
• Agitation, or excitability

The aim of treatment is to reduce symptoms by encouraging the affected person to recall the event, to express feelings, and to gain some sense of mastery over the experience. In some cases, expressing grief helps to complete the necessary mourning process. Support groups provide a setting where people who have had similar experiences can share feelings, and are very helpful.

Depression, alcohol or substance abuse (which commonly occur with PTSD), or associated medical conditions, may need to be treated before symptoms of PTSD can be effectively addressed. Behavioral therapy, a type of talking therapy, may be used to treat avoidance symptoms. This can include graded exposure and flooding, which means that the person is frequently exposed to the object that triggers symptoms, until he/she becomes accustomed to it, and no longer avoids it.

Medicines that act on the nervous system may be used to reduce anxiety and other associated symptoms. Anti-depressants, including Prozac, Paxil, and Zoloft, have proved effective in treating PTSD. Sedatives can help with sleep disturbance. Anti-anxiety medicines may be useful, but the benzodiazepines, a type of drug used to treat anxiety, can be addictive.

• Depression, anxiety, and phobia, or fear of things that are not usually frightening to other people, may accompany this disorder
• Alcohol abuse and/or drug abuse

While traumatic events like the September 11 tragedy can cause distress, not all feelings of distress are symptoms of PTSD. You should talk about your feelings with friends and relatives. If your symptoms persist longer, or are worse, than those of your friends, you should contact your doctor.

You should seek help immediately by going to the emergency room or calling the local emergency number (such as 911) if you are feeling overwhelmed by guilt, if you are impulsive, thinking of hurting yourself, unable to contain your behavior, or if you are experiencing other very distressing symptoms of PTSD.

You can also contact your doctor for help with ongoing problems such as recurrent thoughts, irritability, and problems with sleep.