Anxiety overview

# Overview
Anxiety is a physiological state characterized by cognitive, somatic, emotional, and behavioral components.  These components combine to create the feelings that we typically recognize as fear, apprehension, or worry. Anxiety is often accompanied by physical sensations such as heart palpitations, nausea, chest pain, shortness of breath, or headache.

# Historical Perspective
Sigmund Freud recognized anxiety as a "signal of danger" and a cause of "defensive behavior". He believed we acquire anxious feelings through classical conditioning and traumatic experiences.
We maintain anxiety through operant conditioning; when we see or encounter something associated with a previous traumatic experience, anxious feelings resurface. We feel temporarily relieved when we avoid situations which make us anxious, but this only increases anxious feelings the next time we are in the same position, and we will want to escape the situation again and therefore will not make any progress against the anxiety.

# Classification
According to DSM-5 diagnostic criteria, anxiety is classified as follows:
- Generalized anxiety disorder
- Panic disorder
- Separation anxiety disorder
- Selective mutism
- Specific phobia
- Agoraphobia
- Social anxiety disorder
- Anxiety disorder due to another medical condition
- Substance/medication induced anxiety disorder
- Unspecified anxiety disorder

# Pathophysiology
Various theories have been implicated in the pathogenesis of anxiety  which are as follows: Biologic( increased sympathetic tone and decreased GABA), psychoanalytic component(Freud described that anxiety is developmentally related to childhood fears of disintegration that derive from the fear of actual or imagined loss of a love object or fear of bodily harm), learning theory ( where anxiety is attributed to continuous exposure to stress), about 5% individuals with anxiety have polymorphic variant of the gene associated with serotonin transporter metabolism.

# Causes
Life threatening causes of anxiety include anaphylaxis, acute coronary syndromes, cardiogenic shock, and myocardial infarction. Other common causes of anxiety include anemia, caffeine, diabetes, and hyperthyroidism.

# Differential diagnosis
Anxiety must be differentiated from: Major depressive disorder, bipolar disorder, atypical psychosis, schizophrenia, substance related disorder, cognitive disorder. Some of the medical conditions similar to anxiety are myocardial infarction/angina pectoris, hyperventilation syndrome, hypoglycemia, hyperthyroidism, carcinoid.

# Epidemiology and demographics
The prevalence of anxiety is estimated to 28800 per 100,000 (28.8%) individuals. The female to male ratio is 3 to 2.

# Risk factors
Common risk factors in the development of anxiety are: Depression, Alcohol, low socio-economic status, bipolar disorder, urbanization, stress, family history ofanxiety, unemployment,substance abuse

# Natural history, complications and prognosis
If left untreated, anxiety may cause consequences such as depression, suicide, substance abuse, insomnia, compromised immune system.

# Diagnosis
History and Symptoms | Physical Examination | Laboratory Findings | Imaging Findings

## History and symptoms
The most common symptoms of anxiety  is inappropriate worry about multiple factors, restlessness, fatigue, insomnia, and impairment in functioning of the individual. The symptoms must be persistent for at least a duration of six months.

## Physical examination
The following are the some of the physical examination findings associated with anxiety :Tachycardia, tremors, sweating, restlessness, twitches, shortness of breath.

## Lab tests
The diagnosis of anxiety is mostly clinical, based on a thorough history and physical exam. Lab tests are done to rule out other medical causes that cause anxiety. Some of the lab tests that could help differentiate anxiety causing conditions are as follows: CBC, BMP, urine analysis, urine drug screen, thyroid function tests, urine catecholamines

## Electrocardiogram
The EKG in anxiety is characterized by sinus tachycardia.

## Imaging studies
The diagnosis of anxiety is mostly clinical, based on a thorough history and physical exam. Imaging studies should not be routinely done, but rather be guided by pertinent findings in the history and physical exam and ruling out secondary causes.

# Treatment
Medical Therapy | Primary Prevention | Secondary Prevention | Cost-Effectiveness of Therapy | Future or Investigational Therapies

## Medical therapy
The mainstay of therapy for anxiety is the administration of pharmacotherapy and psychotherapy, pharmacotherapy includes treatment with benzodiazepine, buspirone, tricyclic antidepressant, SSRI . Cognitive behavioral therapy is the main stay of psychotherapy

## Primary prevention
There is no established method for the prevention of anxiety. Although there is no proven way to prevent anxiety, early identification of stressors, getting help to cope with crisis situations and avoiding substances that can induce anxiety to some extent can minimize severity of symptoms.

## Secondary prevention
The secondary prevention of anxiety is same as its primary prevention.