Ashwagandha
ashwagandha · Withania somnifera · KSM-66
An adaptogenic herb promoted for stress, sleep and testosterone.
TypeSupplement / dietary
The grade answers: What does the human evidence support for: Stress & sleep?
Grade
C
Limited
The grade rates evidence quality — it is not advice to take or buy.
- Class
- Adaptogen
- Primary use
- Stress & sleep
- Evidence strength
- medium
- Last reviewed
- 2026-07-01
Bottom line
Reasonable short-term evidence for reducing stress and improving sleep; it is not a longevity molecule, and rare liver-injury reports mean it isn't consequence-free.
What the evidence says
Ashwagandha has a cluster of small randomized trials showing reductions in perceived stress and cortisol and improvements in sleep over 6–12 weeks, with some data on modest strength or testosterone changes in men. The effects are real but short-term and studied mostly with standardised extracts. It has no aging or longevity outcome data. Balanced against that are sporadic reports of drug-induced liver injury and thyroid effects. Grade C: a legitimate short-term stress/sleep aid, not a geroprotector and not risk-free.
Key studies
- [1]
Ashwagandha for stress and anxiety (meta-analysis) · meta-analysis
Reduced perceived stress and cortisol short-term.
Open on PubMed ↗ - [2]
- [3]
Ashwagandha-associated liver injury (case reports) · safety
Rare but real hepatotoxicity signal to be aware of.
Open on PubMed ↗
Mechanism
Proposed modulation of the hypothalamic-pituitary-adrenal (stress) axis and GABAergic activity; withanolides are considered the active constituents.
Safety
Generally well tolerated short-term. Concerns include occasional GI upset, thyroid hormone changes, and rare but documented cases of liver injury. Avoid in pregnancy and with certain autoimmune/thyroid conditions without medical advice.
Dosage context
Trials typically use ~300–600 mg/day of a standardised root extract for 6–12 weeks. Long-term safety beyond a few months is not well characterised.
Examples of application
- Taken as a standardised root extract (~300–600 mg/day) for short periods.
- Aimed at stress and sleep, not longevity.
- Watched for the rare liver-safety signal; avoided in pregnancy.
From the field
Ashwagandha is one of the better-evidenced adaptogens for stress — which is not the same as longevity. We grade it C and, unusually for a herb, flag a genuine (if rare) liver-safety signal.