Ginkgo Studies Find Conflicting Results on Cognition. (Blinding an Issue)
Walsh, Nancy, Clinical Psychiatry News
Two recent randomized, controlled trials evaluating ginkgo's effect on memory and cognition in normal subjects came to opposing conclusions, drawing criticism about study design and blinding, as well as drug-company sponsorship.
In one study, 203 volunteers were given either ginkgo 40 mg three times per day or placebo for 6 weeks and were evaluated on various standardized neuropsychological tests of verbal and nonverbal learning and memory. Memory performance was also self-assessed and reported by a companion.
No differences were seen in cognitive performance, self-reporting, or companion observations after 6 weeks, reported lead investigator Paul Solomon, Ph.D., of Williams College, Williamstown, Mass., and his associates. "This study does not support the manufacturer's claims of the benefits of ginkgo on learning and memory," they wrote (JAMA 288:835-40, 2002).
The second study randomized 262 cognitively intact older adults to 180 mg/day ginkgo for 6 weeks. Outcomes included change from baseline on neuropsychological tests and self-reporting of memory.
More improvements were seen on 11 of the 13 objective outcome variables in the ginkgo group than in the placebo group, and significantly more in the ginkgo group also rated their memory capability as "somewhat improved" or "much improved," compared with the placebo recipients (27% vs. 17%).
The study's findings support the use of ginkgo for memory enhancement, the investigators concluded (Hum. Psychopharmacol. Clin. Exp. 17:267-77, 2002).
"There were definitely some modest benefits almost across the board," said lead author Dr. Joseph A. Mix of Liberty University, Lynchburg, Va.
Dr. Mix's study initially was rejected by JAMA, although it was "technically better done," said Dr. Lon S. Schneider, professor of psychiatry, neurology and gerontology at the University of Southern California, Los Angeles.
"Still, it probably worked out better for us being published in a well-respected international journal," Dr. …