Agoraphobia (from Greek ἀγορά, “marketplace”; and φόβος/φοβία, -phobia) is an anxiety disorder defined as a morbid fear of having a panic attack or panic-like symptoms in a situation from which it is perceived to be difficult (or embarrassing) to escape. These situations can include, but are not limited to, wide-open spaces, crowds, or uncontrolled social conditions. Alternatively, social anxiety problems may also be an underlying cause. As a result, sufferers of agoraphobia avoid public and/or unfamiliar places, especially large, open spaces such as shopping malls or airports from which they cannot easily escape if they have a panic attack. In severe cases, the sufferer may become confined to his or her home, unable to leave their safe haven.
Although mostly thought to be a fear of public places, it is now believed that agoraphobia develops as a complication of panic attacks. However, there is evidence that the implied one-way causal relationship between spontaneous panic attacks and agoraphobia in DSM-IV may be incorrect. Onset is usually between ages 20 and 40 years and more common in women. Approximately 3.2 million, or about 2.2%, of adults in the US between the ages of 18 and 54, suffer from agoraphobia. Agoraphobia can account for approximately 60% of phobias. Agoraphobia, as studies have shown, has two age groups at which the first onset generally occurs — early to mid twenties and in the early thirties — thus helping to distinguish between simple phobias in child and adolescent years.
In response to a traumatic event, anxiety may interrupt the formation of memories and disrupt the learning processes, resulting in dissociation. Depersonalization (a feeling of disconnection from one’s self) and derealisation (a feeling of disconnection from one’s surroundings) are other dissociative methods of withdrawing from anxiety.
Standardized tools such as Panic and Agoraphobia Scale can be used to measure agoraphobia and panic attacks severity and monitoring treatment.
Source and References http://en.wikipedia.org/wiki/Agoraphobia