Anxiety disorder is a blanket term covering several different forms of abnormal, pathological anxiety, fears, and phobias. Anxiety and fear are ubiquitous emotions. The terms anxiety and fear have specific scientific meanings, but common usage has made them interchangeable. For example, a phobia is a kind of anxiety that is also defined in the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV-TR) as a "persistent or irrational fear." Fear is defined as an emotional and physiological response to a recognized external threat. Anxiety is an unpleasant emotional state, the sources of which are less readily identified. It is frequently accompanied by physiological symptoms that may lead to fatigue or even exhaustion. Because fear of recognized threats causes similar unpleasant mental and physical changes, patients sometimes use the terms fear and anxiety interchangeably. Distinguishing among different anxiety disorders is important, since accurate diagnosis is more likely to result in effective treatment and a better prognosis. Surveys have shown as many as 30% of Americans may be affected by anxiety disorders.
Anxiety disorders are often debilitating chronic conditions, which can be present from an early age or begin suddenly after a triggering event. They are prone to flare up at times of high stress.
A good assessment is essential for the initial diagnosis of an anxiety disorder, preferably using a standardized interview or questionnaire procedure alongside expert evaluation and the views of the affected person. There should be a medical examination in order to identify possible medical conditions that can cause the symptoms of anxiety. A family history of anxiety disorders is often suggestive of the possibility of an anxiety disorder.
Anxiety can be accompanied by headache, sweating, palpitations, and hypertension.
It is important to note that a patient with an anxiety disorder will often exhibit symptoms of Clinical Depression and vice-versa. Rarely does a patient exhibit symptoms of only one or the other.

Causes and contributing factors
Clinical and animal studies suggest a correlation between anxiety disorders and difficulty in maintaining balance. A possible mechanism is malfunction in the parabrachial nucleus, a structure in the brain, that among other functions, coordinates signals from the amygdala with input concerning balance. The amygdala is involved in the emotion of fear.
Biochemical factors come into play. Low levels of GABA, a neurotransmitter that reduces overactivity in the central nervous system, contributes to anxiety. A number of anxiolytics achieve their effect by modulating the GABA receptors.

Treatment
The choices of treatment include cognitive behavioral therapy, lifestyle changes, and/or pharmaceutical therapy (medications). Mainstream treatment for anxiety consists of the prescription of anxiolytic agents and/or antidepressants and/or referral to a Psychologist/cognitive-behavioral therapist. Treatment controversy arises because some studies indicate that a combination of the medications and behavioral therapy can be more effective than either one alone; however, others studies suggest pharmacological interventions are largely just pallative, and can actually interfere with the mechanisms of successful therapy.
Meta-analysis indicates that psychotherapeutic interventions have superior long-term efficacy when compared to pharmacotherapy. The right treatment may depend very much on the individual's genetics and environmental factors. Therefore it is important to work closely with a psychologist and medication provider who is familiar with anxiety disorders and current treatments.
A number of drugs can be prescribed to treat these disorders. These include benzodiazepines (such as Xanax), antidepressants of most of the main classes (SSRI, TCAs, MAOIs), and possibly Quetiapine.