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SleepUncovered

Ashwagandha for sleep — the evidence

Updated16 May 2026Read time5 minReviewed bySleepUncovered editorial

Short answer

Limited evidence

Ashwagandha has small but real effects on sleep in controlled trials — mostly mediated through reduced cortisol and anxiolytic action. Effect sizes are modest (10–15 min improvement in sleep onset). Stronger evidence in stressed or anxious populations than in good sleepers.

Key points

  • Standardised extract (KSM-66 or Sensoril) at 300–600 mg daily is the most-studied protocol.
  • Meta-analyses show small benefits on sleep onset, quality, and daytime cortisol — effect sizes are modest.
  • Best evidence in anxiety- or stress-related sleep difficulty, not chronic primary insomnia.
  • Takes 2–4 weeks of consistent use to see effects.
  • Quality control is a major issue — actual content varies widely between brands. Buy verified standardised extracts.

Verdict

Ashwagandha is the most-studied adaptogen for sleep and anxiety, and the evidence is genuinely positive — but modest. If you have anxiety-related sleep difficulty, ashwagandha is a reasonable low-risk trial. If you have chronic primary insomnia, CBT-I outperforms it by a large margin and should come first.

Mechanism

Ashwagandha (Withania somnifera) contains withanolides, plant compounds that appear to:

  • Reduce serum cortisol in stressed populations.
  • Modulate GABA receptor activity (mild anxiolytic effect).
  • Reduce inflammatory markers.

The plant has a long history in Ayurvedic medicine. Modern evidence is moderate-quality but consistent across small trials.

What trials show

A 2021 systematic review (Cheah et al, Cureus) pooled five RCTs of ashwagandha extracts on sleep:

  • Sleep onset latency: improved by ~10 min.
  • Total sleep time: improved by ~25 min.
  • Sleep efficiency: improved by ~3 percentage points.
  • Subjective sleep quality: significantly improved.

Effects were larger in patients with clinically diagnosed insomnia or significant stress; smaller in healthy adults.

Dose and form

The studied protocols use standardised extracts:

  • KSM-66: 300–600 mg daily, taken once (typically with breakfast) or split into morning + evening doses.
  • Sensoril: 125–250 mg daily.

Unstandardised crude root powder doses (1.5g+ daily) have less consistent evidence. Effect takes 2–4 weeks to develop.

Side effects and contraindications

Most side effects are mild: mild GI upset, drowsiness. Rare but documented: hyperthyroidism-like symptoms in some users (ashwagandha increases T4).

Avoid or use with caution if:

  • You have hyperthyroidism or take thyroid medication.
  • You take immunosuppressants (theoretical interaction).
  • You take sedatives (additive effect).
  • You're pregnant (limited safety data).
  • You have autoimmune conditions (theoretical immune modulation).

Quality control

Ashwagandha is sold both as crude root powder and as standardised extracts. The standardised extracts (KSM-66, Sensoril, Shoden) are tested for withanolide content. Many cheaper products simply state “ashwagandha root” with no concentration verification.

Buy a brand that lists withanolide content (typically 2.5–5%) and ideally uses one of the named standardised extracts.

Practical trial protocol

  1. Start with 300 mg KSM-66 daily, with food.
  2. Keep a simple sleep diary across 4 weeks.
  3. If no benefit by week 4, increase to 600 mg.
  4. If no benefit by week 8, stop. The protocol isn't working for you.
  5. Re-test after a 2-week wash-out to distinguish effect from placebo.

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