According to the American Psychiatric Association, each of the anxiety disorders share the features of fear and anxiety. Fear is a healthy, rational response to either a real or perceived threat whereas anxiety is anticipatory and is in response to a possible perceived threat in the future.

Anxiety among the general population is very high with estimates as high as 18% or 40 million American adults experiencing anxiety disorders each year. Some researchers feel that the lifetime prevalence rate may be as high as 30%. Almost 50% of people who experience anxiety disorders also meet the criteria for depressive disorder. Clinicians recognize that there is a very high level of comorbidity (shared symptoms) between depressive disorders and anxiety disorders, and believe that there may be a possible shared genetic predisposition.