In the wild, an animal that never feels anxiety would quickly become a dead animal.

This is due to the fact that anxiety produces a raised sense of awareness and physiological readiness to fight or fly, which is essential for survival.

For many people, however, anxiety is triggered in situations where it is unnecessary or even unhelpful, such as a crowded mall or when talking to a group of friends.

For these people, anxiety becomes a problem. Rather than a sensible reaction to a life-threatening situation, anxiety becomes triggered inappropriately.

Anxiety disorders are "the most common mental illness" in the United States, affecting an estimated 40 million adults.

Because of this high prevalence, researchers are forging ahead in an effort to uncover what goes on in the brain. It is important to understand which brain circuits are controlling the anxiety response, and what goes wrong with those circuits in people with anxiety disorders.

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