• The effects on measures of anxiety from two doses of oral caffeine (250 and 500 mg) and placebo were compared in 12 patients with generalized anxiety disorder (GAD), 12 patients with panic disorder, and 12 normal subjects. Caffeine produced significantly less decrease in electroencephalographic alpha wave activity, greater decrease in N1-P2 auditory evoked potential amplitude, and greater increased in skin conductance level, systolic and diastolic blood pressure, critical fusion flicker frequency, and self-ratings of anxiety and sweating in patients with GAD than in normal patients. Patients with panic disorder showed different reactivity than normal patients did with respect to electroencephalographic alpha waves, N2 latency, N2-P2 auditory evoked potential amplitude, and physical tiredness but were less reactive than patients with GAD on several variables. It is concluded that patients with GAD are abnormally sensitive to caffeine and that the data support the view that panic disorder is a separable disorder from GAD.
Bruce M, Scott N, Shine P, Lader M. Anxiogenic Effects of Caffeine in Patients With Anxiety Disorders. Arch Gen Psychiatry. 1992;49(11):867–869. doi:10.1001/archpsyc.1992.01820110031004