Researchers have conducted both animal and human studies to pinpoint the particular parts of the brain that are involved in anxiety and fear. Because fear evolved to deal with danger, it sets off an immediate protective response without conscious thought. This fear response is believed to be coordinated by the amygdala, a structure deep inside the brain. Although relatively small, the amygdala is quite complex, and recent studies suggest that anxiety disorders may be associated with abnormal activity within it.
Occasional anxiety is an expected part of life. You might feel anxious when faced with a problem at work, before taking a test, or before making an important decision. But anxiety disorders involve more than temporary worry or fear. For a person with an anxiety disorder, the anxiety does not go away and can get worse over time. The symptoms can interfere with daily activities such as job performance, school work, and relationships.