Potential clinical applications of Ashwagandha (Withania somnifera) in medicine and neuropsychiatry

ABSTRACT

Introduction

Ashwagandha (ASW) is the extract of the plant Withania somnifera. It is widely used in complementary, alternative, and integrative medicine (CAIM) but is little discussed in mainstream modern medical literature.

Areas covered

We performed a review of potential pharmacotherapeutic properties of ASW. Studies were sourced from relevant online and offline databases. In animal models, ASW displays antioxidant activity. It has GABAergic and other neurotransmitter modulatory effects. It reduces apoptosis and promotes synaptic plasticity. It improves cognition and reverses induced cognitive deficits. It attenuates indices of stress. In human subjects, ASW enhances adaptogenesis in healthy adults. It modestly benefits generalized anxiety disorder and obsessive-compulsive disorder, and symptom severity in schizophrenia, substance use disorders, and attention deficit hyperactivity disorder. It improves sleep quality.

Expert opinion

ASW may confer modest benefit in certain neuropsychiatric conditions. Its benefits may arise from induction of neuroplasticity, antioxidant and anti-inflammatory effects, and modulation of GABA and glutamate, as well as other neurotransmitters. The antioxidant and anti-inflammatory actions may also benefit neurodegenerative states. Reports of clinical benefit with ASW must be interpreted with caution, given the paucity of randomized clinical trials (RCTs). Greater methodological rigor is necessary before clinical recommendations on ASW can be confidently made.

Plain Language Summary

ASW is an extract of the Indian winter review and meta-analysis of four RCTs reported scientific studies on the use of ASW in animal and human subjects in order to identify potential clinical uses in modern medicine.

Our review finds that ASW has antioxidant and anti-inflammatory action. It also modulates the effects of several neurotransmitters in the brain. It attenuates laboratory and clinical indices of stress. These mechanisms may benefit mental illnesses such as anxiety, depression, obsessive-compulsive disorder, schizophrenia, attention deficit hyperactivity disorder, and addictive disorders. ASW improves exercise capacity in healthy adults. It also appears to improve sleep quality. In addition, ASW may also improve cognitive functioning post-brain injury and in those at risk of dementia. There is evidence from animal models that ASW may also be of benefit in cancer, stroke, and induced organ damage.

These studies, while suggesting a wide range of potential clinical applications for ASW, must be viewed with caution because the clinical data are based on small numbers of patients treated for a relatively short period of time. Many clinical trials that found benefits with ASW were one-off studies that have not been replicated. Larger and more methodologically stringent clinical trials are required before ASW can be confidently recommended for clinical use. Because ASW is a herbal extract and because the efficacy of its many constituents is not known, it is not possible to generalize conclusions to all extracts, whether standardized or not.

KEYWORDS:

• Ashwagandha
• Withania somnifera
• Indian winter cherry
• Ayurveda
• clinical applications
• pharmacology
• clinical pharmacology

Article highlights

• Ashwagandha (ASW) is an extract of the Indian winter cherry plant, which has been widely used in Ayurveda, a traditional system of medicine, and is believed to confer diverse health benefits.

• Extracts of ASH have been extensively studied in preclinical in vitro and in vivo models, which have identified a wide range of mechanisms through which ASW may benefit dysfunction and disease in humans.

• Animal data from in vivo studies suggest that extracts of ASW reduce indices of stress, anxiety, and depression, improves cognition and reverses induced cognitive deficits, reverses or attenuates movement disorders in animal models and also appears to protect against induced seizures, and against drug addiction and withdrawal.

• Clinical data, especially quality clinical data from large, well-designed, well-conducted, well-analyzed, and well-reported RCTs, are sparse and at best only suggest only a potential for ASW to improve sleep, reduce stress and anxiety, and reduce negative symptoms of schizophrenia.

• A strong recommendation can be made for further clinical trials of ASW; however, until data from such studies are available, ASW is best considered to be only a nutraceutical with potential application to neuropsychiatric disorders.

• Finally, ASW is a complex combination of several dozen chemical constituents, the benefits and risks associated with the individual constituents are unknown and findings with one formulation of ASW cannot be validly generalized to all formulations of ASW, whether standardized or not.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

This paper was not funded.