# Ashwagandha: What the Evidence Actually Says About Stress and Cortisol
Canonical: https://www.migaku.app/guides/ashwagandha-stress-cortisol-evidence
Category: evidence
Summary: Multiple RCTs show ashwagandha reduces cortisol and perceived stress. This guide explains what the evidence shows, what it doesn't, and how to interpret the dosage research.
Last reviewed: 2026-05-09
Reviewed by: Migaku Editorial Team
## Quick Answer

Ashwagandha (Withania somnifera) has moderate clinical evidence for reducing self-reported stress and serum cortisol in chronically stressed adults. The most consistent results come from KSM-66 and Sensoril standardised extracts at 300–600 mg/day over 8–12 weeks.

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## What the Research Shows

Several randomised controlled trials have measured cortisol, stress scales (PSS), and anxiety measures. Key findings:

- A 2012 RCT in *Indian Journal of Psychological Medicine* (n=64) found 300 mg KSM-66 twice daily reduced PSS scores by 44% versus 5.5% for placebo.
- A 2019 RCT in *Medicine* (n=60) found Sensoril at 240 mg/day reduced cortisol by 22.2% after 60 days.
- A 2021 meta-analysis in *Journal of Ethnopharmacology* (7 RCTs, n=491) confirmed significant reductions in perceived stress and cortisol, with small-to-moderate effect sizes.

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## Evidence Quality Assessment

| Outcome | Evidence Level | Notes |
|---|---|---|
| Reduced perceived stress (PSS) | Moderate | Consistent across 5+ RCTs |
| Reduced serum cortisol | Moderate | 15–30% reductions in stressed adults |
| Improved sleep quality | Preliminary | 2 RCTs, small sample sizes |
| Testosterone increase in men | Preliminary | 1 RCT, mixed quality |
| Athletic performance | Preliminary | Mixed results, endpoint variability |

Most trials use proprietary extracts; generic root powder results may differ.

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## Standardisation Matters

Look for extracts standardised to withanolide content (the active compound class):

- **KSM-66**: Root extract, 5% withanolides
- **Sensoril**: Root + leaf extract, 10% withanolides
- **Generic "ashwagandha root powder"**: Variable withanolide content, limited trial data

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## Dosage Reference

- Typical studied dose: 300–600 mg/day of standardised extract
- Duration: 8–12 weeks to see stress and cortisol effects
- Timing: Morning or split morning/evening; some trials use evening dosing for sleep endpoints

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## Safety Notes

- Ashwagandha is generally well-tolerated at standard doses. Most common side effects are mild GI discomfort.
- **Thyroid conditions:** Ashwagandha may increase thyroid hormone levels. People on thyroid medication should use caution and monitor levels.
- **Pregnancy:** Avoid — traditionally considered abortifacient at high doses; no modern safety data exists.
- **Autoimmune conditions:** Theoretical concern about immune stimulation; data is limited but worth flagging.
- Rare cases of hepatotoxicity have been reported; causality is not established in most cases but warrants caution with pre-existing liver conditions.

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## What It Does Not Do (Yet)

- There are no long-term trials (>6 months) in humans.
- "Adrenal fatigue" as a clinical diagnosis is not validated by endocrinology consensus; ashwagandha should not be framed as treating it.
- Effects on HPA axis dysregulation in clinical populations (not just stressed healthy adults) are understudied.

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## Practical Next Steps

1. Choose a KSM-66 or Sensoril product, 300–600 mg/day.
2. Take with food to reduce GI effects.
3. Assess stress and sleep after 8 weeks before deciding to continue.
4. Cycle off every 3 months if using long-term, until more longitudinal data is available.