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Brains yield clues to obsession.

Two new studies described in the September ARCHIVES OF GENERAL PSYCHIATRY offer a peek at brain activity associated with the intrusive thoughts and ritualized behaviors that characterize obsessive-compulsive disorder (OCD).

In an extension of previous work (SN: 4/11/87, p.236), psychiatrist Lewis R. Baxter Jr. of the University of California, Los Angeles, and his colleagues find that both successful behavior therapy and successful drug therapy for OCD produce substantial drops in energy use by the right caudate nucleus, an inner-brain structure that helps regulate impulses involving sex, aggression, and various objects of disgust. As OCD symptoms improve, metabolism also declines in two related areas, the orbital cortex, which lies just above the eyes, and the thalamus, the scientists report.

These structures may participate in a brain circuit that malfunctions in OCD, allowing obsessive worries to overwhelm attention and control thoughts and behavior, the researchers say. However, they do not know whether problems with the caudate nucleus or any other brain area cause OCD.

The investigators used positron emission tomography (PET) scanners to study the brains of persons in three groups: nine OCD patients before and after 10 weeks of treatment with the antidepressant drug fluoxetine (Prozac), nine OCD patients before and after 10 weeks of behavior therapy consisting of strategies to diminish the force of their impulses, and four healthy controls before and after a 10-week interval. Comparable changes in brain metabolism appeared in the seven patients who improved on fluoxetine and the six whose symptoms abated with behavior therapy.

A second PET study, directed by psychiatrist Susan E. Swedo of the National Institute of Mental Health in Bethesda, Md., also found sharp drops in metabolism in the right orbital cortex among 13 OCD patients who improved after a year of drug therapy. Unlike Baxter's group, however, the NIMH researchers uncovered no changes in the caudate nucleus.

Baxter theorizes that successful OCD treatment first affects the caudate, slowing the unconscious rush of disturbing impulses, and gradually moves to the orbital cortex as conscious strategies to quell symptoms gain strength.
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Title Annotation:obsessive-compulsive disorder may occur when some brain area malfunction
Publication:Science News
Article Type:Brief Article
Date:Sep 26, 1992
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