The technical term for having a fear of strangers is Xenophobia (this term also applies to having a fear of foreigners or immigrants).
The DSM lists Social Anxiety as one of three types of phobias. Social phobia, DSM 300.23, is an irrational anxiety elicited by exposure to certain types of social or performance situations; it can lead to avoidant behavior.
Agoraphobia with a history of panic disorder, DSM 300.21 and agoraphobia without a history of panic disorder, DSM 300.22, is an irrational anxiety toward being in places from which escape might be difficult or embarrassing. Note: the DSM is moving away from having agoraphobia as a diagnosable psychiatric disorder.
For those interested, the third phobia the DSM lists is called a Specific Phobia, DSM 300.29. A specific phobia is a persistent and irrational fear in the presence of a specific stimulus, which commonly elicits avoidance of that stimulus, i.e., withdrawal. There are five subtypes for specific phobias:
- animal type - cued by animals or insects
- natural environment type - cued by objects in the environment, such
as storms, heights, or water
- blood-injection-injury type - cued by witnessing some invasive
- situational type - cued by a specific situation, such as public
transportation, tunnels, bridges, elevators, flying, driving, or
- other type - cued by other stimuli than the above, such as of
choking, vomiting, or contracting an illness
Thank you to The Phobia List and The Anxiety Pit for the above information on agoraphobia, social anxiety, and specific phobias.
Although agoraphobia is not considered a codable disorder anymore -- I believe it is slated to be removed from the DSM V -- here is the diagnostic criteria for agoraphobia from the DSM IV (current version):
1. anxiety about being in places or situations from which escape might be difficult (or embarrassing) or in which help may not be available in the event of having an unexpected or situationally predisposed Panic Attack or panic-like symptoms.
2. The situations are avoided (e.g., travel is restricted) or else are endured with marked distress or with anxiety about having a Panic Attack or panic-like symptoms, or require the presence of a companion.
3. The anxiety or phobic avoidance is not better accounted for by another mental disorder, such as Social Phobia, Specific Phobia, Obsessive-Compulsive Disorder, Posttraumatic Stress Disorder, or Separation Anxiety Disorder.
Here is the diagnostic criteria for Avoidant Personality Disorder:
AVOIDANT PERSONALITY DISORDER
Individuals with this Cluster C Personality Disorder, DSM 301.82, are socially inhibited, usually feel inadequate and are overly sensitive to criticism. A pervasive pattern of social inhibition, feelings of inadequacy, and hypersensitivity to negative evaluation are present, beginning by early adulthood and manifest in a variety of contexts, as indicated by four (or more) of the following:
1. Avoids occupational activities that involve significant interpersonal contact, because of fears of criticism, disapproval, or rejection.
2. Is unwilling to get involved with people unless certain of being liked.
3. Shows restraint within intimate relationships because of a fear of being shamed or ridiculed.
4. Is preoccupied with being criticized or rejected in social situations.
5. Is inhibited in new interpersonal situations because of feelings of inadequacy.
6. Views self as socially inept, personally unappealing, or inferior to others.
7. Is unusually reluctant to take personal risks or to engage in any new activities because they may prove embarrassing.
If I were to compare agoraphobia to avoidant personality disorder, I would say agoraphobia is about the perceived physical safety of the person with agoraphobia, which when threatened causes intense emotional distress. With avoidant personality disorder I would postulate that the disorder revolves around the individual's perception of how they are perceived, rather than on their physical safety. A person with agoraphobia might be anxious and frightened to leave the house because they might be involved in a car accident. A person with avoidant personality disorder may be reluctant to leave the house and go to a new social situation for the fear of personal rejection.