Ashwagandha

Overview

Ashwagandha (Withania somnifera) is a shrub native to India whose root extract is classified as an adaptogen and has a long-documented history in Ayurvedic medicine^1,2. It contains steroidal lactones called withanolides, along with alkaloids and other secondary metabolites, which are believed to underlie its pharmacological activity³. Modern clinical research has focused mainly on its effects on stress and anxiety: a 2022 meta-analysis of 12 RCTs (n=1,002) found a significant reduction in anxiety scores (SMD: -1.55, 95% CI: -2.37 to -0.74) with ashwagandha supplementation⁴, and a second 2024 meta-analysis of 9 RCTs (n=558) confirmed significant effects on both subjective and objective stress and anxiety measures⁵. Individual randomized, double-blind, placebo-controlled trials have reported reductions in anxiety scale scores and changes in stress hormones (cortisol, DHEA-S, testosterone) after 60 days of use^6,1. A separate meta-analysis of 5 RCTs (n=400) found a small but statistically significant improvement in overall sleep quantity and quality⁷. A pilot RCT in subclinical hypothyroid patients found ashwagandha root extract (600 mg/day) reduced TSH levels over 8 weeks compared to placebo². Beyond stress and thyroid research, early-phase and observational work is exploring other applications: a Phase 1 dose-ranging trial of a pharmaceutical-grade Withania somnifera leaf extract (RH324) assessed safety/tolerability and short-term tumor metabolism changes in advanced non-small cell lung cancer⁸, and a single Ayurvedic case report described symptomatic improvement in a Parkinson's disease patient given ashwagandha combined with Kapikachhu over 60 days⁹. These latter two are exploratory/preliminary and should not be read as established indications.

Safety

The reviewed trials generally describe ashwagandha as well tolerated over 8–60 day periods, including in a subclinical hypothyroid population where safety was specifically assessed alongside efficacy². A Phase 1 trial of a related leaf-extract formulation (RH324) in cancer patients specifically assessed short-term safety and tolerability, indicating that formal safety monitoring is an active area of research⁸. No dedicated large-scale safety trial or systematic adverse-event analysis is included in this brief. Documented supplement-drug interaction data (see Interactions) note relevance to thyroid-modulating agents and CNS-active substances, suggesting caution particularly in those contexts. No data on use in pregnancy, breastfeeding, or in children was found in the reviewed studies — this population-specific safety information is not addressed in the brief.

Dosage

Studies used varying doses depending on the outcome studied: 240 mg/day of a standardized extract (Shoden) for 60 days for stress/anxiety⁶; 500 mg/day root extract standardized to 2.5% withanolides (with 5 mg piperine, delivering ~12.5 mg withanolides/day) for 60 days for stress and anxiety¹; and 600 mg/day root extract for 8 weeks in subclinical hypothyroid patients². The meta-analyses pooled trials using a range of doses and did not specify a single uniform dose across the 9–12 included studies^4,5,7. No single optimal or standardized dose can be derived from this brief.

Interactions

Documented supplement-drug interaction data list relevance to nitric oxide, 3,4-methylenedioxyamphetamine (MDMA), antioxidants, central nervous system stimulants, corticosterone, glutathione, and propylthiouracil. Given a trial showing ashwagandha lowers TSH in subclinical hypothyroid patients², caution with thyroid-modulating medications (such as propylthiouracil, noted above) is warranted. No other specific drug interaction studies are included in this brief.

Traditional Use

In Ayurvedic medicine, ashwagandha (Withania somnifera) is traditionally used as a rejuvenating tonic and is often prescribed for thyroid dysfunction and stress-related complaints^2,1. It is described in Ayurvedic case-based practice combined with other botanicals (such as Kapikachhu) for conditions like Kampavata, the Ayurvedic correlate of Parkinson's disease⁹. Reviews of the plant's traditional use note applications across a range of ailments alongside its documented phytochemistry of withanolides and alkaloids³.

Evidence Strength

Ashwagandha's effects on stress and anxiety are supported by consistent findings across three separate meta-analyses pooling multiple randomized controlled trials, plus individual RCTs replicating the effect with hormonal outcome measures — this constitutes a relatively strong and consistent evidence base for this specific use. Evidence for sleep improvement is more modest (a small effect size from 5 pooled RCTs). Evidence for thyroid effects comes from a single small pilot RCT and needs replication. Evidence for cancer and Parkinson's disease applications is very preliminary (a Phase 1 safety trial and a single case report) and should not be considered established.