A phobia is an intense and persistent fear of certain activities, animals, people, specific objects, situations, or things that in reality present little or no danger. Phobias are the most common mental illness among women in all age groups and the second most common illness among men older than 25. Common phobias include fear of animals such as snakes and spiders, fear of flying, and fear of heights.

In the case of a severe phobia, you might go to extreme lengths to avoid the thing you fear. Unfortunately, avoidance only strengthens the phobia. Phobias are generally caused by an event recorded (by the amygdala and hippocampus) as dangerous. Whenever a person encounters the trigger, the body reacts as if the event were happening again.