Note:  topic started originally by bluelicorice

what is PTSD ... here is an explanation from the American Psychiatric Association:

POSTTRAUMATIC STRESS DISORDER (PTSD)

Post-Traumatic Stress Disorder (PTSD) is a debilitating condition that follows a terrifying event. Often, people with PTSD have persistent frightening thoughts and memories of their ordeal and feel emotionally numb, especially with people they were once close to. PTSD, once referred to as shell shock or battle fatigue, was first brought to public attention by war veterans, but it can result from any number of traumatic incidents. These include kidnapping, serious accidents such as car or train wrecks, natural disasters such as floods or earthquakes, violent attacks such as a mugging, rape, or torture, or being held captive. The event that triggers it may be something that threatened the person's life or the life of someone close to him or her. Or it could be something witnessed, such as mass destruction after a plane crash.

Whatever the source of the problem, some people with PTSD repeatedly relive the trauma in the form of nightmares and disturbing recollections during the day. They may also experience sleep problems, depression, feeling detached or numb, or being easily startled. They may lose interest in things they used to enjoy and have trouble feeling affectionate. They may feel irritable, more aggressive than before, or even violent. Seeing things that remind them of the incident may be very distressing, which could lead them to avoid certain places or situations that bring back those memories. Anniversaries of the event are often very difficult.

PTSD can occur at any age, including childhood. The disorder can be accompanied by depression, substance abuse, or anxiety. Symptoms may be mild or severe--people may become easily irritated or have violent outbursts. In severe cases they may have trouble working or socializing. In general, the symptoms seem to be worse if the event that triggered them was initiated by a person--such as a rape, as opposed to a flood.

Ordinary events can serve as reminders of the trauma and trigger flashbacks or intrusive images. A flashback may make the person lose touch with reality and reenact the event for a period of seconds or hours or, very rarely, days. A person having a flashback, which can come in the form of images, sounds, smells, or feelings, usually believes that the traumatic event is happening all over again.

Not every traumatized person gets full-blown PTSD, or experiences PTSD at all. PTSD is diagnosed only if the symptoms last more than a month. In those who do have PTSD, symptoms usually begin within 3 months of the trauma, and the course of the illness varies. Some people recover within 6 months, others have symptoms that last much longer. In some cases, the condition may be chronic. Occasionally, the illness doesn't show up until years after the traumatic event.

Specific Symptoms of this Disorder:

The person has been exposed to a traumatic event in which the person experienced, witnessed, or was confronted with an event or events that involved actual or threatened death or serious injury, or a threat to the physical integrity of self or others and the person's response involved intense fear, helplessness, or horror.

The traumatic event is persistently reexperienced in one (or more) of the following ways:

recurrent and intrusive distressing recollections of the event, including images, thoughts, or perceptions.

recurrent distressing dreams of the event.

acting or feeling as if the traumatic event were recurring (includes a sense of reliving the experience, illusions, hallucinations, and dissociative flashback episodes, including those that occur on awakening or when intoxicated).

intense psychological distress at exposure to internal or external cues that symbolize or resemble an aspect of the traumatic event

physiological reactivity on exposure to internal or external cues that symbolize or resemble an aspect of the traumatic event

The individual also has persistent avoidance of stimuli associated with the trauma and numbing of general responsiveness (not present before the trauma), as indicated by three (or more) of the following:

efforts to avoid thoughts, feelings, or conversations associated with the trauma

efforts to avoid activities, places, or people that arouse recollections of the trauma

inability to recall an important aspect of the trauma
markedly diminished interest or participation in significant activities

feeling of detachment or estrangement from others
restricted range of affect (e.g., unable to have loving feelings)

sense of a foreshortened future (e.g., does not expect to have a career, marriage, children, or a normal life span)

Persistent symptoms of increased arousal (not present before the trauma), as indicated by two (or more) of the following:

difficulty falling or staying asleep

irritability or outbursts of anger

difficulty concentrating

hypervigilance

exaggerated startle response

The disturbance, which has lasted for at least a month, causes clinically significant distress or impairment in social, occupational, or other important areas of functioning.

References:
American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders, fourth edition.
Washington, DC: American Psychiatric Association.

National Institutes of Health, National Institute of Mental Health, NIH Publication No. 95-3879 (1995)