Reductions in occipital cortex GABA levels in panic disorder detected withH-1-magnetic resonance spectroscopy

Background: There is preclinical evidence and indirect clinical evidence im plicating gamma -aminobutyric acid (GABA) in the pathophysiology and treatm ent of human panic disorder. Specifically, deficits in GABA neuronal functi on have been associated with anxiogenesis, whereas enhancement of GABA func tion tends to be anxiolytic. Although reported peripheral GABA levels leg, in cerebrospinal fluid and plasma) have been within reference limits in pan ic disorder, thus far there has been no direct assessment of brain GABA lev els in this disorder. The purpose of the present work was to determine whet her cortical GABA levels are abnormally low in patients with panic disorder . Methods: Total occipital cortical GABA levels (GABA plus homocarnosine) wer e assessed in 14 unmedicated patients with panic disorder who did not have major depression and 14 retrospectively age- and sex-marched control subjec ts using spatially localized H-1-magnetic reso-nance spectroscopy. All pati ents met DSM-IV criteria for a principal current diagnosis of panic disorde r with or without agoraphobia. Results: Patients with panic disorder had a 22% reduction in total occipita l cortex GABA concentration (GABA plus homocarnosine) compared with control s. This finding was present in 12 of 14 patient-control pairs and was not s olely accounted for by medication history. There were no significant correl ations between occipital cortex GABA levels and measures of illness or stat e anxiety. Conclusions: Panic disorder is associated with reductions in total occipita l cortex GABA levels. This abnormality might contribute to the pathophysiol ogy, of panic disorder.