Generalised Anxiety Disorder
Challenge Studies for Anxiety Disorder
Experimental challenges, such as lactate infusion, CO2 inhalation and 5-HT depletion are believed to trigger specific mechanisms related to particular disorders. The response to a challenge in a group of patients with a specific disorder may be considered as a marker for that disorder. Early small-scale studies have suggested that contrary to PD subjects, patients with GAD are not vulnerable to lactate infusion.
It has been well established that PD patients taking a breath of 35% CO2 have both a strong autonomic reaction and a definite, brief increase in anxiety, contrary to normals. A group of patients with GAD was selected after careful exclusion of any lifetime history of PA, and underwent the 35% CO2 challenge. Unlike normals, GAD patients displayed a strong autonomic reaction, but unlike PDs, they failed to report any increase in anxiety. Comparable results discriminating between GAD and PD were recently obtained by Perna and coworkers.
These data support the theory that GAD and PD are distinct entities based on different underlying processes. The results may also suggest a disturbed autonomic function in GAD.