MELBOURNE, AUSTRALIA. A connection between abnormalities in the sympathetic nervous system and panic attacks has long been suspected. As early as 1871 "irritable heart", a condition very similar to panic attacks, was attributed to hypersensitivity of the "cardiac nerve centers". Now a team of Australian researchers confirms that the secretion of epinephrine (adrenaline) does indeed increase dramatically during panic attacks (by an average 153 per cent) and may be accompanied by rapid heart beat and atrial fibrillation. The researchers performed a carefully controlled study of 13 patients with panic disorder and 14 healthy controls. They found no difference in sympathetic nervous activity among patients and controls when at rest. They did observe that epinephrine was released from the heart in panic disorder patients during rest. They speculate that this release is a result of the heart's uptake of large amounts of epinephrine during panic attacks. The researchers also found that the heart rate and systolic blood pressure increased significantly in both patients and controls when exposed to simulated mental stress (rapidly subtracting 1-digit numbers from a 3-digit number for 10 minutes). They conclude that there may be a selective increase in cardiac sympathetic activity during panic attacks and that release of epinephrine from the sympathetic nerves of the heart could trigger cardiac arrhythmias.

Dr. George Heninger, MD of Yale University School of Medicine concludes in an accompanying commentary that panic attacks originate in the brain and that the excessive epinephrine discharge is a secondary effect. He suggests that abnormalities in the body's GABA (gamma-aminobutyric acid) system could be the main trigger for panic attacks.
Wilkinson, Dominic J.C., et al. Sympathetic activity in patients with panic disorder at rest, under laboratory mental stress, and during panic attacks. Archives of General Psychiatry, Vol. 55, June 1998, pp. 511-20
Heninger, George R. Catecholamines and pathogenesis of panic disorder. Archives of General Psychiatry, Vol. 55, June 1998, pp. 522-23 (commentary)