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MONDAY, June 21 (HealthDayNews) -- People with Parkinson's disease who have high levels of homocysteine, an amino acid produced by the body, are likelier to suffer from depression than Parkinson's patients with normal homocysteine levels, a new study says.

Researchers say a drug used to treat Parkinson's may be behind the elevated risk.

The study, appearing in the June issue of the Archives of Neurology, included 97 people who had had Parkinson's disease (PD) for an average of 3.6 years. Fifty-four of them were taking the drug levodopa. The study subjects were divided into two groups, those with elevated homocysteine levels and those with normal levels.

All the participants completed a depression questionnaire and tested for their cognitive and motor skills.

"An elevated plasma [homocysteine] concentration... was present in 31 (32 percent) of our 97 patients with fairly recent onset PD," the study authors wrote. "An elevated [homocysteine] level is most likely due to the prevalent use of levodopa: as in previous studies, the patients taking levodopa had higher [homocysteine] levels than those not taking levodopa."

Patients with elevated homocysteine levels were slightly older (68 years vs. 62 years), were more depressed, and had worse cognitive functioning, the study found.

"Our findings, if confirmed, indicate that disease burden in PD patients, such as poor motor performance, depression, and cognitive deterioration, is associated with a high [homocysteine] level," the authors concluded.

More information

The U.S. National Institute of Neurological Disorders and Stroke has more about Parkinson's disease.

(SOURCE: JAMA/Archives, news release, June 21, 2004)

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