Anxiety can be caused by a physical disorder or the use or discontinuation of a drug. Physical disorders that can cause anxiety include the following:
• Brain and nerve (neurologic) disorders, such as head injuries, brain infections, and some inner ear disorders
• Heart disorders, such as heart failure and abnormal heart rhythms (arrhythmias)
• Hormonal (endocrine) disorders, such as an overactive adrenal or thyroid gland
• Lung (respiratory) disorders, such as asthma and chronic obstructive pulmonary disease (COPD)
Even fever can cause anxiety.
Drugs that can induce anxiety include the following:
• Alcohol
• Stimulants
• Caffeine
• Cocaine
• Many prescription drugs, such as theophylline (used, for example, to treat asthma)
• Some over-the-counter weight-loss products, such as those containing the herbal product guarana, caffeine, or both
Drugs that can induce anxiety when stopped include benzodiazepines.
Anxiety may occur in dying people as a result of fear of death, pain, and difficulty breathing (see Death and Dying: Depression and Anxiety).
Treatment
A doctor aims to correct the causes rather than treat the secondary anxiety symptoms. Anxiety should subside after the medical disorder is treated or the drug has been stopped long enough for any withdrawal symptoms to abate.
If anxiety remains, antianxiety drugs or psychotherapy (such as behavior therapy) is used. For people who are dying, strong pain relievers (analgesics) with potent antianxiety effects, such as morphine, are often appropriate. No dying person should have to experience intense anxiety.
Resource: Merck Manual Home Edition