Test Your Knowledge

The exact cause of most anxiety disorders is unknown. However, a combination of psychological, biological and environmental factors may be responsible. Heredity is also believed to play a role in many anxiety disorders. The combination of heredity and the anxiety experienced may vary.

Research is ongoing into how the brain creates feelings of anxiety and fear. Scientists believe that an almond-shaped structure called the amygdala serves as a central location that coordinates messages between the parts of the brain that process incoming sensory signals and the parts that interpret those signals. The amygdala signals the body when a threat is present, triggering anxiety or fear.

Another brain structure called the hippocampus also helps process threatening signals and changes information into memories. Research shows that people who have experienced severe stress (such as child abuse or combat experience) appear to have a smaller hippocampus.