Ashwagandha for Stress: Does It Actually Work?

Ashwagandha (Withania somnifera) has been used in Ayurvedic medicine for 3,000 years. Modern interest started in the 2000s when standardised extracts entered Western markets. As of 2025, it’s among the most-studied adaptogens, with multiple double-blind RCTs showing effects on stress, cortisol, sleep, and exercise performance — though with notable caveats.

What the evidence says

Stress & cortisol: Multiple RCTs (Chandrasekhar 2012; Lopresti 2019; Gopal 2021) show 600 mg/day of KSM-66 ashwagandha for 8 weeks reduces self-reported perceived stress by ~40 % and morning cortisol by 14–28 % vs placebo.

Sleep: 600 mg/day improves sleep onset latency and sleep quality scores (Pittsburgh Sleep Quality Index) in adults with mild insomnia (Langade 2019).

Anxiety: A 2021 systematic review (Akhgarjand et al.) of 9 RCTs found significant reductions in anxiety scores with effect sizes comparable to mainstream anxiolytic treatments — though with smaller study sizes and shorter durations than psychiatric medication trials.

Exercise / strength: Modest effect on muscle strength and recovery in untrained adults (Wankhede 2015), small effect in trained adults.

Choose the right extract

KSM-66 (Ixoreal Biomed) is the most-studied extract — 5 % withanolides, root-only. 300–600 mg once daily.

Sensoril (Natreon) is a leaf+root extract standardised to 8–10 % withanolides. Higher withanolide concentration but smaller body of evidence. 250 mg once or twice daily.

Generic "ashwagandha root powder" without standardisation has unpredictable potency. The clinical trials all use standardised extracts — that’s what to buy.

Who should NOT take ashwagandha

Pregnant and breastfeeding women: traditional Ayurvedic medicine considers it abortifacient and there is human case-report evidence of liver toxicity. Avoid.

Hyperthyroid (Graves’ disease, Hashimoto’s): can raise thyroid hormone levels and worsen symptoms.

On anti-anxiety / sedative medications (benzodiazepines, gabapentin, opioids): may potentiate sedation. Talk to a physician.

On thyroid replacement (levothyroxine): may interfere — recheck TSH after starting.

Liver disease: rare but documented case reports of drug-induced liver injury. Avoid.

How to take it (if it’s right for you)

300–600 mg KSM-66 once daily, with food. Morning is best (some people feel mildly sedating effects in the evening).

Try for 6–8 weeks before assessing — the cortisol effect builds over 4 weeks.

Cycle: take for 8–12 weeks, then take a 2–4 week break. Long-term continuous use isn’t well-studied beyond 12 weeks.

Recommended Canadian brand: Pure Encapsulations Ashwagandha (300 mg KSM-66, ~$30–40 / 60 caps). Sold at Pure Pharmacy, ND clinics, and online. Most other Canadian brands also carry KSM-66.

The bottom line

Ashwagandha is the rare supplement with credible RCT data. If you have stress + sleep difficulty and aren’t in any of the contraindication groups, 600 mg/day of KSM-66 for 8 weeks is a reasonable trial. If it doesn’t move the needle by week 8, stop. Don’t take it indefinitely — the long-term safety data isn’t there yet.

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