Ashwagandha
Root extract (KSM-66 / Shoden)
Across five randomized trials, ashwagandha root extract improved objectively measured sleep — efficiency and time awake after sleep onset — and lowered serum cortisol by roughly a quarter at 600 mg per day. Effects need eight or more weeks and are largest in people who sleep poorly or feel stressed.
Strong: a meta-analysis of 5 RCTs (n = 400) with consistent direction; objective actigraphy/PSG outcomes in 3 of them; replicated cortisol reductions across independent meta-analyses. Downgraded from 'definitive' because most trials are small and come from a handful of extract manufacturers.
Withanolides appear to dampen the HPA stress axis (lower cortisol) and act on GABA-ergic signalling — calmer nights show up as fewer awakenings and higher overnight HRV.
Best in diagnosed insomnia and high perceived stress at ≥600 mg/day for ≥8 weeks. Little effect in already-good sleepers. Avoid with thyroid disease, pregnancy, autoimmune conditions.
Every estimate, against a line of no effect
Diamonds are point estimates; the hairline is the 95% confidence interval where the trial reported one.
- Sleep efficiency (SMD)SMD · Cheah 2021−0.68−1.06 … −0.30
- Sleep onset latency (SMD)SMD · Cheah 2021−0.53[not reported]
- Wake after sleep onset (SMD)SMD · Cheah 2021−0.39[not reported]
- Serum cortisol% · Chandrasekhar 2012−27.9%[not reported]
Units are never mixed on one line: each scale gets its own axis. Where a trial reported no confidence interval we leave it blank rather than inventing one.
4 studies across 10 years
- · Rare liver-injury case reports (NIH LiverTox) — stop on dark urine/jaundice.
- · Raises thyroid hormones — avoid with hyperthyroidism or levothyroxine.
- · Avoid in pregnancy and autoimmune disease.
References
- 1.Effect of Ashwagandha (Withania somnifera) extract on sleep: A systematic review and meta-analysisPLOS ONE · 2021 · meta-analysis · 5 trials · n = 400
Small-to-moderate overall sleep improvement (SMD −0.59); efficiency, latency, total sleep and WASO all improved; larger effects at ≥600 mg and ≥8 weeks.
- 2.A prospective, randomized double-blind, placebo-controlled study of safety and efficacy of a high-concentration full-spectrum extract of Ashwagandha root in reducing stress and anxiety in adultsIndian Journal of Psychological Medicine · 2012 · rct · n = 64
600 mg/day for 60 days reduced serum cortisol by 27.9% vs 7.9% with placebo.
- 3.Does Ashwagandha supplementation have a beneficial effect on the management of anxiety and stress? A systematic review and meta-analysis of randomized controlled trialsPhytotherapy Research · 2022 · meta-analysis · 12 trials
Significant reductions in anxiety and stress scores versus placebo.
- 4.Ashwagandha — LiverTox: Clinical and Research Information on Drug-Induced Liver InjuryNIH / NCBI Bookshelf · 2019 · case reports
Rare cholestatic liver injury case reports; resolves on discontinuation.
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