According to a study from Mexico*, published this month, the benefit of ginkgo biloba extracts may potentially be extended to include antidepressant activity.
The study used what the authors state to be "the most widely used preclinical model for assessing antidepressant-like behaviour", namely the mouse forced swimming test. This is also perhaps more aptly known as the behavioural despair test.
Basically, mice are placed into deep water in a glass cylinder, from which they cannot get out. They are left there for 15 minutes. The next day, they are treated with the test substance or a placebo and put back in the water for 5 minutes. The time during which they remain motionless during this second session is supposedly a measure of their level of "hopelessness". If treatment with a substance reduces the immobile time, that substance is considered to be a promising candidate for further investigation as an antidepressant.
My thoughts on the test itself would divert too far from the subject of this post! Nevertheless, the results are interesting.
The time spent immobile by mice treated with a ginkgo biloba extract was nearly 40% less than that spent by untreated mice. They also had lower values for two indicators of oxidative stress (lipid peroxidation and superoxide radical production). It is thought that oxidative stress plays and important part in the development of depression.
In addition, the gingko biloba extract affected the transmission of nerve signals through the brain that is regulated by serotonin and dopamine. These substances are also known to be involved in determining whether a person feels depressed or not.
This study confirms similar results of a US study performed with another ginkgo extract in 2007 and adds extra knowledge about the possible mechanisms. A number of studies on the benefit of gingko biloba in elderly patients with dementia over the past decade have also reported positive effects on mood.
Ginkgo biloba is also being researched in other conditions and diseases, reviewed in my hub: What is the benefit of ginkgo biloba supplements?
*Rojas et al, Antidepressant-like effect of a ginkgo biloba extract (EGb761) in the mouse forced swimming test: Role of oxidative stress, Neurochemistry International, June 6, 2011 (Epub ahead of print)