Agoraphobia often manifests in clusters, in which the sufferer is phobic of a group of related situations. Common clusters include being on a bridge; being in an automobile; being in a crowd; and being away from home alone.
Agoraphobia is often related to panic disorder, but may appear separately.Source:
American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders (4th Ed.). Washington, DC: Author.

