There have been few clinical studies of ORX metabolism or function in human anxiety populations. However, recently generated human pilot data in the principal investigator's (PI's) lab, studying the effects of a well-documented anxiogenic stimulus (35% CO2 inhalation) on behavioral, physiological, and biochemical (plasma ORX A; assayed by a standard radioimmunoassays [RIA] kit) measures, in 1 PD patient and 2 healthy volunteers. In this paradigm, the PD patient had a mild panic episode associated with marked early elevations in plasma ORX levels, relative to the volunteers who had minimal anxiety, consistent with a role for ORX in the initiation or elaboration of the human panic response.