Phobias are common: one in nine people have a phobia of some sort. A phobia is an extreme reaction to fear triggered by a stimulus. We can also say that a phobia is a fear of a fear, as the unwanted feelings can often be created by simply thinking about the unwanted situation. Some people may be quite happy to live with their phobia as it does not disturb their daily lives. However, if it leads to unreasonable or disabling behaviour their lives will be happier if the phobia can be removed.

Phobias may be acquired as a result of a single trauma (possibly when a child), or by a gradual learned response (possibly influenced by parental behaviour), or by avoidance following a traumatic event (e.g. refusal to get back on the horse), but in every case it is the subconscious mind which provides the response and which needs to learn a new, and less troublesome, pattern of behaviour.

The most common phobias that I see are:

Flying (and see http://www.ft.com/cms/s/0/91f968ee-cfe0-11de-a36d-00144feabdc0.html#axzz2UDjcYC9g)
Needles
Motorway driving

…but the list of potential phobias is very long.