Use of the Clinical Laboratory in the Diagnosis and Treatment of Depression

Clinical laboratory tests have practical utility in the diagnosis of depression and in monitoring treatment. Research laboratory tests, though not a focus for this article, provide possible insights into the pathophysiology of depression. At present, pathognomonic tests for the diagnosis of depression do not exist, so the principal role of the laboratory in diagnosis is to establish the presence of disorders that resemble or cause depression. Clinical laboratory tests can assist in monitoring physiologic changes that might indicate resolution of the illness or impending relapse, and in monitoring therapeutic levels of medications. Treatment of depression can lead to side effects or toxicity that also warrant clinical laboratory testing.