OPTIC FLOW-INDUCED SWAY IN ANXIETY DISORDERS ASSOCIATED WITH SPACE AND MOTION DISCOMFORT

This study examined whether anxiety patients with space and motion dis comfort (SMD; e.g., fear of heights), like patients with vestibular dy sfunction, have increased body sway responses to motion in the visual field. Six patients with panic disorder, agoraphobia, or generalized a nxiety disorder, ail with symptoms of SMD, and seven asymptomatic nona nxious control subjects were examined. While standing on a force platf orm, subjects monocularly viewed optic flow (movement) stimuli project ed on a screen in a 60 degrees central visual field. The experiment co nsisted of (a) a baseline (no-flow) period involving three different v isual conditions without flow, (b) an optic flow period involving five different conditions of moving visual stimuli, and (c) a postflow per iod during which the baseline conditions were repeated. Three of the f ive optic flow stimuli oscillated at a frequency of 3 cycles/10 s (0.3 Hz) in a manner designed to increase anterior-posterior sway. Postura l sway measures were decomposed into powers at four frequency bands, o ne of which (centered at 0.3 Hz) reflected sway that occurred in tande m with the motion of the oscillating flow stimuli. Results indicated t hat compared with controls, sway in patients showed (a) greater overal l levels; (b) greater flow effects, i.e., greater increases during osc illatory flow conditions compared to baseline; (c) a trend toward grea ter persistence effects, i.e., greater increases from preflow to postf low periods. Four of the six patients showed sway levels exceeding tha t of normals by two standard deviations. The results indicate that SMD in patients with anxiety disorders is associated with increased relia nce on visual cues for maintaining balance. The situation-specific sym ptoms of SMD may lead to avoidance behaviors and the development of ph obia, such as height phobia or agoraphobia.