- Genetics: Research has shown that certain phobias may run in families. For example, twins who are raised separately, in different locations, may develop the same phobias. However, many people with phobias have no relatives with the condition.
- Cultural Factors: Some phobias occur only in certain cultural groups. An example is taijin kyofusho, a social phobia that appears almost exclusively in Japan. This is a fear of offending or harming others in social situations. It is markedly different from a traditional social phobia, in which the sufferer is afraid of being personally embarrassed on humiliated. It is therefore possible that culture plays some role in phobia development.
- Life Experience: Many phobias are based in real-life events that may or may not be consciously remembered. A phobia of dogs, for example, may stem from being attacked as a small child. A social phobia may develop from teenage awkwardness or childhood bullying.
It is likely that a combination of these factors must be in place for a phobia to develop. However, more research is necessary before a definitive conclusion can be reached.Source:
Anxiety Disorders. National Institute of Mental Health. February 13, 2008. http://www.nimh.nih.gov/health/publications/anxiety-disorders/complete-publication.shtml#pub5