ASHWAGANDHA

Updated August 17, 2016

Ashwagandha is a common name for the plant Withania somnifera, which is also known as "winter cherry" and "Indian ginseng." It is used in Indian traditional medicine to treat anxiety, chronic inflammation, depression, fatigue, stress, and weakness. While it is also used to improve cognition, the evidence in humans is very limited and it is unknown if ashwagandha can slow cognitive decline or prevent Alzheimer's disease. Ashwagandha is likely safe for most people though it has some drug interactions and should not be used during pregnancy.

EVIDENCE

A few studies have examined short-term cognitive effects of ashwagandha, but no studies have tested whether it can prevent age-related cognitive decline or dementia. Our search identified:

• 0 clinical studies in humans examining the treatment or prevention of cognitive decline or dementia
• 1 randomized controlled clinical trial in healthy adults examining the effects on cognitive function
• 1 randomized controlled clinical trial in bipolar disorder patients
• Numerous preclinical studies on possible mechanisms of action

POTENTIAL BENEFIT

It is currently unknown whether ashwagandha can prevent cognitive decline or dementia in humans. In a small double-blind placebo-controlled clinical trial, supplementation at 250 mg twice daily for 2 weeks improved psychomotor performance (reaction time) in healthy men [2]. In another randomized controlled study, patients with bipolar disorder treated with 500 mg/day experienced greater improvements in a type of working memory, a measure of reaction time, and a measure of social cognition, compared to those receiving placebo [3]. However, no benefits with ashwagandha were seen in other cognitive measures including executive function, processing speed, and psychomotor speed. Both of these trials were too small and short to determine whether ashwagandha has long-term benefits for cognitive health. Laboratory studies have shown that ashwagandha may benefit cognitive function by promoting neuronal growth and protecting neurons from damage and oxidative stress [4-7], but these benefits have not been confirmed in humans.