Anxiety in the medically ill: nosology and principles of differential diagnosis

Anxiety and anxiety disorder have been estimated to occur in 5% to 20% of medical inpatients and 4% to 14% of medical outpatients. These estimates do not distinguish between anxiety symptoms and anxiety disorders, nor between the various causes of anxiety in the medically ill. This article reviews the epidemiology, nosology, disorders in the differential diagnosis, and principles of differential diagnosis of anxiety in the medically ill. A widely endorsed nosology for anxiety disorders caused by medical illness and its treatments is a relatively recent development. General guidelines for differentiating between specific diagnoses in the differential diagnosis of anxiety in the medically ill are now provided in the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, but, as is often the case, it is easier to describe the distinctions in theory than it is to make them in actual practice.