Behavior and anxiety: physiologic mechanisms.

The distinction between "normal" and clinical anxiety and the theories put forth to explain the etiology and nature of both experiences are described. Research directed toward elucidation of the psycho- and neurophysiology of anxiety is reviewed; two major neurophysiologic models based on animal studies are presented. None of the various models proposed to date adequately explains human anxiety. Further clinical studies on the symptoms and natural history of anxiety are suggested.