Ashwagandha Significantly Reduces Cortisol Levels
Ashwagandha supplementation consistently and significantly reduces serum cortisol levels, with reductions ranging from 66-67% in clinical trials, though this biological effect does not reliably translate to improvements in subjectively perceived stress.
Evidence for Cortisol Reduction
The most recent and comprehensive evidence demonstrates robust cortisol-lowering effects:
A 2025 systematic review and meta-analysis found a statistically significant reduction in cortisol levels of -1.16 µg/dL (95% CI: -1.64 to -0.69, P < 0.001) 1. This represents the highest-quality pooled evidence available.
Individual RCTs support these findings with even more dramatic effects. A 2024 study using Shoden (ashwagandha extract with 35% withanolide glycosides) at doses of 60-120 mg daily showed morning serum cortisol decreased by 66-67% compared to only 2.22% in placebo (p < 0.0001) 2.
A 2019 study using 240 mg daily of standardized extract demonstrated significant morning cortisol reduction (P < 0.001) compared to placebo 3.
Another 2019 trial showed dose-dependent cortisol reduction with both 250 mg/day (P < 0.05) and 600 mg/day (P < 0.0001) 4.
The Cortisol-Stress Perception Disconnect
Critically, the biological cortisol reduction does not consistently correlate with subjective stress relief:
The 2025 meta-analysis found no significant impact on Perceived Stress Scale (PSS) scores (SMD = -0.355,95% CI: -1.188 to 0.47; P = 0.40) despite the robust cortisol reduction 1. This disconnect suggests that cortisol lowering alone may not be sufficient for stress symptom relief, or that longer treatment durations are needed.
However, a 2024 meta-analysis of different studies showed significant improvements in PSS (MD = -4.72,95% CI = [-8.45 to -0.99]) and Hamilton Anxiety Scale scores (MD = -2.19,95% CI = [-3.83 to -0.55]) 5.
Mechanism of Action
Ashwagandha appears to work through modulation of the hypothalamus-pituitary-adrenal (HPA) axis 3. The herb's stress-relieving effects occur via its moderating effect on this axis, leading to reduced cortisol secretion. Additionally, studies show effects on DHEA-S levels (P = 0.004) and testosterone increases in males (P = 0.038) 3.
Dosing Considerations
Effective doses range from 60 mg to 600 mg daily:
- Low-dose, high-concentration extracts (35% withanolide glycosides): 60-120 mg daily is effective 2
- Standard extracts: 240-300 mg daily 3
- Higher doses: Up to 600 mg daily shows dose-dependent effects 4
A 2026 dose-response meta-analysis identified significant linear (coefficient = 0.005, P = 0.031) and non-linear (P-nonlinearity = 0.005) associations between dosage and stress levels 6.
Safety Considerations and Caveats
Important warnings from recent safety reviews:
A 2026 critical review identified several potential adverse effects 7:
- Hepatotoxicity: Metabolic transformation via cytochrome P450 enzymes can form reactive intermediates causing oxidative stress and liver toxicity
- Endocrine disruption: Cases of thyrotoxicosis and potential adrenal suppression have been reported
- Gastrointestinal effects: Common with prolonged or excessive use
- Drug interactions: Through CYP450 enzyme modulation
Clinical pitfalls to avoid:
- Do not assume cortisol reduction equals stress relief - the biological and subjective effects may diverge
- Monitor liver function with prolonged use, particularly in patients with pre-existing liver conditions
- Assess thyroid function in patients with thyroid disorders before initiating therapy
- Consider drug interactions in patients on medications metabolized by CYP450 enzymes
- Avoid in pregnancy due to insufficient safety data on endocrine effects
Clinical Application Algorithm
For patients seeking cortisol reduction:
- Baseline assessment: Measure morning serum cortisol, liver enzymes, and thyroid function
- Initiate therapy: Start with 240-300 mg daily of standardized extract (or 60-120 mg of high-concentration extract with 35% withanolides)
- Monitor at 4-8 weeks: Recheck morning cortisol, assess subjective stress symptoms, and monitor liver enzymes
- Dose adjustment: If inadequate response and no adverse effects, may increase to 600 mg daily
- Long-term monitoring: Reassess liver function and thyroid parameters every 3-6 months with continued use
The evidence strongly supports ashwagandha for biological cortisol reduction, but clinicians should set realistic expectations that subjective stress improvement may require longer treatment duration (>60 days) and may not occur in all patients despite cortisol normalization 1, 5.