Everyone periodically experiences fear and anxiety.
Fear is an emotional, physical, and behavioral response to an immediately recognizable external threat (eg, an intruder, a car spinning on ice).
Anxiety is a distressing, unpleasant emotional state of nervousness and uneasiness; its causes are less clear. Anxiety is less tied to the exact timing of a threat; it can be anticipatory before a threat, persist after a threat has passed, or occur without an identifiable threat. Anxiety is often accompanied by physical changes and behaviors similar to those caused by fear.
Some degree of anxiety is adaptive; it can help people prepare, practice, and rehearse so that their functioning is improved and can help them be appropriately cautious in potentially dangerous situations. However, beyond a certain level, anxiety causes dysfunction and undue distress. At this point, it is maladaptive and considered a disorder.
Anxiety occurs in a wide range of physical and mental disorders, but it is the predominant symptom of several. Anxiety disorders are more common than any other class of psychiatric disorder. However, they often are not recognized and consequently not treated. Left untreated, chronic maladaptive anxiety can contribute to or interfere with treatment of some general medical disorders.
Mental distress that occurs immediately or shortly after experiencing or witnessing an overwhelming traumatic event is no longer classified as an anxiety disorder. Such disorders are now classified as trauma-related and stressor-related disorders.