Anxiety is a ubiquitous, natural affective state that is essential for evolutionary survival. Nearly as common, however, are experiences of anxiety that exceed social, psychological, or physiological needs, leading to functional impairment. Indeed, primary anxiety disorders, including panic disorder, social phobia, and generalized anxiety disorder (GAD), represent the most common category of mental illness in the United States. Secondary, or reactive, anxiety is also widespread and can arise not only from numerous medical causes but also from the psychological process of coping with illness. Consequently, it is not surprising that diagnosing and treating anxiety poses a common question for the consultation-liaison psychiatrist. In this article, we review 5 themes concerning the interaction between anxiety and medical illness, and comment on the implications for treatment.

Anxiety secondary to medical illness
In some cases, anxiety may be the first or most prominent symptom of an underlying medical illness that has not yet been diagnosed. Clinical examples include the patient with a sudden pulmonary embolus who presents with apparent panic-like symptoms and shortness of breath; the patient with episodic anxiety attacks and a feeling of unreality who is having complex partial seizures; or a tremulous, diaphoretic patient with tachycardia who turns out to have hyperthyroidism. Less common medical illnesses that can present with anxiety include adrenal dysfunction, carcinoid syndrome, pancreatic tumor, and pheochromocytoma.

While the possibilities are numerous, it is important to remember that anxiety can represent merely a symptom and that only after a careful workup can its diagnostic significance be determined. A thorough physical examination, as well as laboratory studies and an ECG when appropriate, is essential for ruling out medical causes and avoiding the misdiagnosis of a primary psychiatric illness. Given their potential morbidity and mortality, endocrine disorders, acute cardiac and pulmonary conditions, and neurological disorders deserve particular scrutiny.

Not only can anxiety be a manifestation of medical illness, but it often occurs as a
consequence
of certain medical conditions. Chronic obstructive pulmonary disease in particular appears to lead to the development of anxiety disorders. Panic disorder and GAD are increased in patients with obstructive pulmonary disease.
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Panic disorder is also increased in patients undergoing lung transplantation. Other conditions include cardiomyopathy, which was noted to have an 83% prevalence in patients with panic disorder,
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and congestive heart failure or cancer. In the same study, 16% of postmyocardial infarction patients had panic disorder, significantly higher than the prevalence in the general population. Posttraumatic stress disorder is also increased in the months after patients have been admitted to a hospital for acute coronary syndromes
³
as well as in many cases of traumatic injuries.

It is not always clear what came first, but clinical experience indicates that the medical condition precedes the development of anxiety in many cases. A prime example is patients with automatic implantable cardioverter defibrillators (AICDs). AICD shocks often result in feelings of nervousness and palpitations and trigger anticipatory anxiety regarding future shocks, which may lead to panic attacks and avoidance behavior.
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Indeed, some observers have viewed this as a kind of conditioning model for panic disorder.

Patients with various life-threatening conditions often experience intense anxiety and preoccupation and hypervigilance regarding somatic sensations. Patients with more aggressive brain tumors, known brain or aortic aneurysms, or malignancies often experience intense anxiety in adapting to their illnesses. There are also reports of patients with brain lesions, caused either by tumors or trauma, in whom clinical signs reminiscent of obsessive-compulsive disorder have developed. In addition, specific circumstances, such as impending surgery, often trigger intense anxiety. Most observers note that preoperative education is often an effective antidote to excessive anxiety.