any of a group of disorders that have as their central organizing theme the emotional state of fear, worry, or excessive apprehension.

This category includes, for example, panic disorder, various phobias (e.g., specific phobia, social phobia), and generalized anxiety disorder. Anxiety disorders have a chronic course, albeit waxing and waning in intensity, and are among the most common mental health problems in the United States. They may also occur as a result of the physiological effects of a medical condition, such as endocrine disorders (e.g., hyperthyroidism), respiratory disorders (e.g., chronic obstructive pulmonary disease), cardiovascular disorders (e.g., arrhythmia), metabolic disorders (e.g., vitamin B₁₂ deficiency), and neurological disorders (e.g., Parkinson’s disease). Obsessive-compulsive disorder and posttraumatic stress disorder were traditionally considered anxiety disorders; however, they are increasingly considered, as in DSM–5, to be separate, if still related, entities.

American Psychological Association