Anxiety disorders are a cluster of mental disorders characterized by significant and uncontrollable feelings of anxiety and fear such that a person's social, occupational, and personal function are significantly impaired. Anxiety may cause physical and cognitive symptoms, such as restlessness, irritability, easy fatiguability, difficulty concentrating, increased heart rate, chest pain, abdominal pain, and a variety of other symptoms that may vary based on the individual.

In casual discourse, the words anxiety and fear are often used interchangeably. In clinical usage, they have distinct meanings: anxiety is defined as an unpleasant emotional state for which the cause is either not readily identified or perceived to be uncontrollable or unavoidable, whereas fear is an emotional and physiological response to a recognized external threat. The umbrella term anxiety disorder refers to a number of specific disorders that include fears (phobias) or anxiety symptoms.

There are several types of anxiety disorders, including generalized anxiety disorder, illness anxiety disorder, specific phobia, social anxiety disorder, separation anxiety disorder, agoraphobia, panic disorder, and selective mutism. The individual disorder can be diagnosed using the specific and unique symptoms, triggering events, and timing. If a person is diagnosed with an anxiety disorder, a medical professional must have evaluated the person to ensure the anxiety cannot be attributed to another medical illness or mental disorder. It is possible for an individual to have more than one anxiety disorder during their life or at the same time and anxiety disorders are marked by a typical persistent course. Anxiety disorders are the most common of mental disorders and affect nearly 30% of adults at some point in their lives. However, anxiety disorders are treatable and a number of effective treatments are available. Treatment helps most people lead normal productive lives.