A phobia (from the , phóbos, "fear"), or morbid fear, is an irrational, intense, persistent fear of certain situations, activities, things, or people. The main symptom of this disorder is the excessive, unreasonable desire to avoid the feared subject. When the fear is beyond one's control, or if the fear is interfering with daily life, then a diagnosis under one of the anxiety disorders can be made.

Phobias (in the clinical meaning of the term) are the most common form of anxiety disorders. An American study by the National Institute of Mental Health (NIMH) found that between 8.7% and 18.1% of Americans suffer from phobias. Broken down by age and gender, the study found that phobias were the most common mental illness among women in all age groups and the second most common illness among men older than 25.

Causes

It is generally accepted that phobias arise from a combination of external events and internal predispositions. In a famous experiment, Martin Seligman used classical conditioning to establish phobias of snakes and flowers. The results of the experiment showed that it took far fewer shocks to create an adverse response to a picture of a snake than to a picture of a flower, leading to the conclusion that certain objects may have a genetic predisposition to being associated with fear. Many specific phobias can be traced back to a specific triggering event, usually a traumatic experience at an early age. Social phobias and agoraphobia have more complex causes that are not entirely known at this time. It is believed that heredity, genetics, and brain chemistry combined with life-experiences to play a major role in the development of anxiety disorders, phobias and panic attacks.

The anatomical side of phobias

Phobias are more often than not linked to the amygdala, an area of the brain located behind the pituitary gland in the limbic system. The amygdala secretes hormones that control fear and aggression. When the fear or aggression response is initiated, the amygdala releases hormones into the body to put the human body into an "alert" state, in which they are ready to move, run, fight, etc.Winerman, Lea. "Figuring Out Phobia", American Psychology Association: Monitor on Psychology, August 2007. This defensive "alert" state and response is generally referred to in psychology as the fight-or-flight response.

Clinical phobias

• Social phobia, also known as social anxiety disorder - fears involving other people or social situations such as performance anxiety or fears of embarrassment by scrutiny of others, such as eating in public. Social phobia may be further subdivided into
• generalized social phobia, and
• specific social phobia, which are cases of anxiety triggered only in specific situations. The symptoms may extend to psychosomatic manifestation of physical problems. For example, sufferers of paruresis find it difficult or impossible to urinate in reduced levels of privacy. That goes beyond mere preference. If the condition triggers, the person physically cannot empty their bladder.
• Specific phobias - fear of a single specific panic trigger such as spiders, snakes, dogs, elevators, water, waves, flying, balloons, catching a specific illness, etc.
• Agoraphobia - a generalized fear of leaving home or a small familiar 'safe' area, and of possible panic attacks that might follow.