Ginkgo biloba is not a smart drug: an updated systematic review of randomised clinical trials testing the nootropic effects of G. biloba extracts in healthy people.

Here, we update our earlier systematic review of 2001, which critically evaluated the data from clinical trials to determine whether Ginkgo biloba enhances cognitive function in healthy subjects. Literatures searches of six computerised databases, updated to January 2007, were made for randomised, placebo-controlled, double-blind clinical trials of the effects of standardised Ginkgo biloba (G. biloba) extracts on cognitive function in healthy subjects under the age of 60 years. Trials published in any language were included, and data were extracted independently by the two authors following a standardised protocol. We include 15 randomised clinical trials of which 7 are single-dose studies and 8 are longer term studies with treatment periods ranging from 2 days to 13 weeks. Three single dose studies and 4 longer term studies are newly included. Several of the studies have methodological flaws. A number of the acute studies used multiple outcomes and report positive effects on one or more of these at particular time points with particular doses but these findings are either not replicated, or are directly contradicted by other studies. The evidence from longer term studies is largely negative. Of those studies which measured subjective effects, only one of five acute studies and one of six longer term studies reported any significant positive results. Overall, and in line with our previous conclusions, we have found no convincing evidence from randomised clinical trials for a robust positive effect of G. biloba ingestion upon any aspect of cognitive function in healthy young people, after either acute or longer term administration.