BACKGROUND:Several herbal remedies are used for mental health, with ginkgo the most popular.
In the US, it is available over the counter in health food shops and elsewhere and has been one of the top five or six bestselling herbal remedies. Worldwide sales exceed $250 million per year. Many countries have approved ginkgo for treating Alzheimer’s disease and other memory problems. In Ireland, it is available only by prescription.
The ginkgo biloba tree is native to southeast Asia and one of the oldest living tree species. It is highly revered in China where traditional Chinese medicine uses ginkgo seeds to treat various illnesses. Recent interest has focused on extracts of its leaves, especially a German extract EGb 761, found in many products. Originally, the herb was investigated for its effect on blood circulation. This led to suggestions it might improve bloodflow in the brain. Gingko is the most widely consumed herbal remedy used to prevent age-related cognitive decline and dementia.
EVIDENCE FROM STUDIES
Popular interest in ginkgo increased dramatically after a 1997 study, which enrolled just over 300 patients with Alzheimer’s disease or dementia. After a year, those taking ginkgo had no deterioration in their symptoms, while those taking a placebo scored significantly worse on cognitive tests. However, studies conducted since have had inconsistent results.
Many of these were not large enough or conducted for long enough. For these reasons, two of the largest dementia-prevention trials ever conducted were initiated with gingko. The GuidAge study is being conducted in Europe; but results are not yet available.
The Gingko Evaluation of Memory (GEM) study was conducted in the US and reported its main findings at the end of 2008. It involved 3,069 participants over 75 years of age. They were at increased risk for dementia, but had no or only mild symptoms of cognitive decline when the study began. Participants were randomised to take placebo or 120mg ginkgo twice daily for an average of six years. At the end, the groups did not differ significantly. It was concluded that gingko is not effective in preventing the development of dementia or delaying the onset of symptoms.
In June 2010, the French company funding the GuidAge study issued a press release. For the primary outcome, ginkgo did not significantly delay the onset of Alzheimer’s disease. However, further data analyses are being carried out, which the company stated are encouraging for those who take gingko for at least four years. We will have to await publication of the details to evaluation whether some people may benefit from gingko.
PROBLEMATIC ASPECTS
In the randomised controlled trials, the incidence of adverse effects has been the same with gingko and placebo. Concerns have been raised about using gingko along with blood-thinning drugs as ginkgo was originally used to increase circulation, but little evidence supports these concerns. However, among participants who started the GEM trial with diagnosed cardiovascular disease, significantly more developed dementia when given gingko compared with placebo. This is a new finding, and may reflect a worrisome connection between ginkgo and heart disease. Further research is needed.
RECOMMENDATIONS
Safe and effective ways of preventing dementia and promoting mental health are needed. To date, evidence does not support using ginkgo biloba. A Cochrane review concluded in 2009 that evidence that gingko is effective for dementia or cognitive impairment is inconsistent and unreliable. Since ginkgo is available in Ireland only by prescription, concerns about mental health or dementia should be discussed with a healthcare professional.
Dónal OMathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University
