Neurobiology of generalized anxiety disorder.

Generalized anxiety disorder (GAD) is a common illness with diagnostic criteria that have changed substantially over time. Symptoms of GAD overlap with those of major depressive disorder to such an extent that studying one disorder without studying the other may be impossible. Such an overlap, combined with potentially inappropriate diagnostic criteria for GAD, makes diagnosing and researching GAD challenging. Recent research into the genetics and neural circuitry of GAD may suggest solutions for the disorder's diagnostic controversies and point the way to productive future studies of etiology and pathophysiology.