SPECT identifies possible basis of social anxiety disorder

A physiological reason may explain why the shrinking violet in your family is so shy. Using brain SPECT, Dutch researchers have detected irregularities in dopamine and serotonin neurotransmitter systems in the brains of such individuals that appear to be linked to social anxiety disorder, a condition that affects an estimated 15 million adults in the U.S. and frequently leads to alcoholism and depression.

Dr. Nic J.A. van der Wee, a psychiatrist specializing in anxiety disorders and psychiatric neuroimaging, and colleagues at Leiden University in the Netherlands used a binding radioactive compound (123I-β-(4-iodophenyl)-tropane) as a tracer to visualize dopamine and serotonin transporters in the brain. The procedure was performed on 12 patients diagnosed with social anxiety disorder who had not taken medication to treat the condition and 12 healthy controls.

In the patients with social anxiety disorder, SPECT revealed altered uptake activity in the thalamus, midbrain, and pons, areas known to be acted upon by serotonin, and in the striatum, an area known to be acted upon by dopamine. The significantly higher binding potentials found in the social anxiety disorder patients indicate imbalances that may affect the way their brains function in normal situations, causing anxiety.

"We found the first direct evidence for abnormalities of the brain's dopaminergic system in patients with social anxiety disorder," said van der Wee. "The study demonstrates that social anxiety has a physical brain-dependent component."

One unique aspect of the research was that it included only patients without prior exposure to pharmacotherapy.

"Our findings broaden the neurobiological model of social anxiety disorder and may lead to novel research not only in pharmacotherapy but also in the etiology of the disorder," van der Wee said.

The study was published in the May issue of the Journal of Nuclear Medicine (2008;49[5]:757-763).

The Netherlands team conducted the research with SPECT, citing that it is easy to use and does not require extensive facilities to produce the radioactive compound. Compared with PET, SPECT offers a higher patient comfort level, lower cost, and higher safety index, according to van der Wee.

Van der Wee and his team are expanding on their research as part of the large-scale Netherlands Depression and Anxiety Study. It is examining 3000 subjects, including patients with social anxiety disorder. The effort will feature a structural and functional brain imaging study using novel MRI techniques in a subset of 300 patients, including patients with society anxiety disorder.

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