A phobia is a persistent, excessive, unrealistic fear of an object, person, animal, activity or situation. It is a type of anxiety disorder. A person with a phobia either tries to avoid the thing that triggers the fear, or endures it with great anxiety and distress. There are three major types of phobia: Specific phobia (simple phobia). With this most common form of phobia, people may fear specific animals (such as dogs, cats, spiders, snakes), people (such as clowns, dentists, doctors), environments (such as dark places, thunderstorms, high places) or situations (such as flying in a plane, riding on a train, being in a confined space). These conditions are at least partly genetic (inherited) and seem to run in families. Social phobia (social anxiety disorder). People with social phobia fear social situations where they may be humiliated, embarrassed or judged by others. They become particularly anxious when unfamiliar people are involved.  Agoraphobia. Agoraphobia is a fear of being in public places where it would be difficult or embarrassing to make a sudden exit. Childhood phobias occur most commonly between the ages of 5 and 9, and tend to last a short while. Most longer-lasting phobias begin later in life, especially in people in their 20s. Adult phobias tend to last for many years, and they are less likely to go away on their own. Without proper treatment, phobia can increase an adult's risk of other types of psychiatric illness, especially other anxiety disorders, depression and substance abuse.  
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