Management of depression in patients with coexisting medical illness.

Depressive illness is common in the general population, with a prevalence of 5 percent. However, 10 to 15 percent of any general medical population has clinically significant depression; in patients with selected chronic illnesses, prevalence rates between 25 to 50 percent are noted. In patients with coexisting medical illness, the diagnosis of depression requires differentiating symptoms of the medical illness from symptoms of the comorbid depression. The Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) can be helpful in this endeavor. An understanding of the effect of particular medications on neurotransmitters is required and can guide the clinician in selecting therapeutic agents that have a low incidence of side effects and toxicity.