Conclusion
Most trials of ashwagandha (Withania somnifera, a herb used in traditional medicine) report reductions in perceived stress, anxiety scores, and the stress hormone cortisol. However, the trials are small and vary widely, so the certainty of this evidence is low.
The drop in cortisol is fairly consistent across studies, while the effect on how stressed people actually feel is less settled, with at least one analysis finding no significant change.
How much does it help?
Pooled analyses report reductions of about 4 to 5 points on a common perceived-stress scale (0 to 40) and about 2 to 3 points on anxiety scales, along with measurable drops in blood cortisol.
Most results come from 300 to 600 mg per day of a standardized extract taken for around 8 weeks. Shorter courses may show little difference.
What the research shows
The evidence base is made up of small RCTs and the systematic reviews that pool them. Each review typically includes around 9 to 15 trials, with a few hundred participants in total.
Variation between trials (statistical heterogeneity) is high, and studies differ in the scales used and the specific extract tested. Many were conducted in India using particular commercial extracts, and some were supported by manufacturers, which is worth keeping in mind.
Cautions
- People who are pregnant or breastfeeding, and those with thyroid or autoimmune conditions, should consult a physician before starting
- Rare cases of liver injury have been reported. Stop and seek medical advice if fatigue, jaundice, or itching appears after starting
- Combining it with sedative medication may increase drowsiness
- Products differ in their content and standardization, so results from one extract may not carry over to another
A simple analogy
Cortisol is a bit like how hard a foot presses the accelerator, and ashwagandha appears to ease off slightly. But even when the measured pressure drops, whether the driver feels more relaxed is a separate question, and that is where the research disagrees.