Ginseng is widely used in herbal medicine as an ‘adaptogen,’ which is a plant that ameliorates the effects of stress. In particular, ginseng has been recognized as having substantial effects on the central nervous system, but there are few well-designed clinical trials evaluating the effects of American Ginseng (Panax Quinquefolius L.) on human neurological performance.
In a recent study, Ossoukhova et al  studied the effects of a single dose of a standardized extract of P. Quinquefolius on the performance of middle-aged (40-60 years old) healthy individuals on a battery of standardized cognitive tests. This same research group had previously studied the effects of single-dose P. Quinquefolius cognitive performance in younger adults . Their hypothesis was that similar cognitive improvement would be observed in an older population, given the normal decline in CNS performance due to aging.
The study was a placebo-controlled, double-blinded, single center, crossover design. A total of 52 subjects were enrolled, and were assessed on 2 days a week apart after informed consent. Subjects were given either placebo or a 200 mg dose of a standardized ginseng extract. All subjects were given the Cognitive Drug Research Battery and the Computerized Mental Performance Assessment System to evaluate cognitive function at 1, 3 and 6 hours after treatment.
The 200 mg dose of ginseng was found to acutely improve overall working memory and spatial working memory at 3 hours after the dose. This study has several limitations; first is the ‘crossover’ design in which all subjects take the treatment (ginseng) and the placebo at some point in the trial. Effects due to the order of treatment (placebo or ginseng) may be present. Second, subjects may exhibit a ‘learning effect,’ in that they become more familiar with the cognitive test battery due to practice.
1. Ossoukhova, A., et al., Improved working memory performance following administration of a single dose of American ginseng (Panax quinquefolius L.) to healthy middle-age adults. Hum Psychopharmacol, 2015. 30(2): p. 108-22.
2. Scholey, A., et al., Effects of American ginseng (Panax quinquefolius) on neurocognitive function: an acute, randomised, double-blind, placebo-controlled, crossover study. Psychopharmacology (Berl), 2010. 212(3): p. 345-56.