Quick Facts
- Evidence Level Moderate
- Also Known As Withania somnifera, Indian ginseng
- Research Dosages 120–600 mg/day (root extract)
- Optimal Duration 8+ weeks for sleep benefits
- Primary Measures PSQI, sleep onset latency, efficiency
Key Studies
Ashwagandha's effect on sleep has been evaluated in two meta-analyses and multiple individual RCTs. The evidence is stronger than for many herbal supplements, though still based on relatively small total sample sizes.
Effect of Ashwagandha extract on sleep: A systematic review and meta-analysis
This is the most comprehensive meta-analysis to date. It found ashwagandha had a significant positive effect on overall sleep quality (SMD -0.59, 95% CI -0.75 to -0.42). Subgroup analyses revealed that benefits were more pronounced with doses of 600 mg/day or higher, treatment lasting 8 weeks or more, and in participants with diagnosed insomnia rather than healthy sleepers. Ashwagandha also improved sleep onset latency and total sleep time, though these individual outcomes showed more variability.[1]
Safety and efficacy of Withania somnifera for anxiety and insomnia
This more recent review examined ashwagandha for both anxiety and insomnia. It confirmed significant improvements in sleep onset latency, total sleep time, PSQI scores, and sleep efficiency. Anxiety scores also improved significantly (HAM-A mean difference: -5.96). This dual effect suggests ashwagandha may improve sleep partly by reducing anxiety — a plausible mechanism given its classification as an adaptogen.[2]
What the evidence does NOT show
- No large-scale RCTs (500+ participants) have been conducted specifically for sleep
- Most studies used proprietary extracts (KSM-66, Sensoril, Shoden), making comparison across studies difficult
- Healthy sleepers showed less benefit than those with insomnia — ashwagandha may not meaningfully improve already-good sleep
- Long-term data beyond 12 weeks is sparse
How Ashwagandha May Affect Sleep
Ashwagandha's sleep-promoting effects likely operate through multiple pathways:
- GABAergic activity: Withanolides, the active compounds in ashwagandha, have demonstrated GABA-mimetic activity in animal models. GABA is the primary inhibitory neurotransmitter that promotes relaxation and sleep onset.
- Cortisol reduction: Multiple studies have shown ashwagandha reduces serum cortisol levels. Elevated cortisol — particularly in the evening — is associated with difficulty falling asleep and poor sleep maintenance.
- Anxiety reduction: The 2024 meta-analysis found significant anxiety reduction alongside sleep improvements, suggesting an indirect pathway where reduced anxiety facilitates better sleep.[2]
- Triethylene glycol: Research has identified triethylene glycol in ashwagandha leaf extracts as a sleep-inducing compound, though most supplements use root extracts where this compound is less concentrated.
It's important to note that most mechanistic evidence comes from animal and in-vitro studies. The human RCTs confirm the endpoint (improved sleep) but the exact pathway in humans remains an area of active research.
Dosages Used in Research
The meta-analyses reviewed studies using a range of dosages and extract types:
| Extract Type | Dosage | Notes |
|---|---|---|
| KSM-66 (root extract) | 600 mg/day | Most commonly studied. Full-spectrum root extract standardized to 5% withanolides. |
| Sensoril (root + leaf) | 125–250 mg/day | Higher withanolide concentration. Lower doses needed. |
| Shoden (root + leaf) | 120 mg/day | Standardized to 35% withanolide glycosides. Lowest effective dose studied. |
The Cheah et al. meta-analysis found that doses of 600 mg/day or higher produced significantly greater sleep improvements than lower doses.[1] However, extract standardization varies, making direct dose comparisons between products unreliable.
Safety Considerations
- Generally well-tolerated: Both meta-analyses reported no serious adverse events across all included trials. The most common side effects were mild GI discomfort and drowsiness.
- Thyroid effects: Ashwagandha may increase thyroid hormone levels (T3 and T4). People with hyperthyroidism or those on thyroid medication should consult their healthcare provider before use.
- Liver concerns: Rare cases of liver injury have been reported with ashwagandha. The WHO and some regulatory agencies have issued advisories. Those with liver disease should avoid use.
- Pregnancy and breastfeeding: Not recommended due to insufficient safety data. Some traditional texts classify ashwagandha as an abortifacient.
- Drug interactions: May interact with sedatives, immunosuppressants, thyroid medications, and blood sugar-lowering drugs. Ashwagandha can enhance the effects of CNS depressants.
- Autoimmune conditions: As an immunomodulator, ashwagandha may stimulate immune activity and is generally not recommended for people with autoimmune conditions like lupus, rheumatoid arthritis, or multiple sclerosis.
The Bottom Line
Ashwagandha has moderate evidence supporting its use for sleep quality, backed by two meta-analyses showing statistically significant improvements. The effect size (SMD -0.59) is meaningful — larger than that seen for magnesium or melatonin's effect on total sleep time.
The evidence is strongest for:
- People with diagnosed insomnia (rather than healthy sleepers)
- Doses of 600 mg/day or higher (of root extract)
- Treatment durations of 8 weeks or more
- Those whose sleep issues are linked to stress or anxiety
Key limitations include small total sample sizes, variability in extract types, and limited long-term data. If sleep difficulties are primarily driven by anxiety or stress, ashwagandha may be particularly relevant given its dual anxiolytic-sleep evidence.
References
- Cheah KL, Norhayati MN, Husniati Yaacob L, Abdul Rahman R. "Effect of Ashwagandha (Withania somnifera) extract on sleep: A systematic review and meta-analysis." PLoS One. 2021;16(9):e0257843. PubMed
- Fatima K, et al. "Safety and efficacy of Withania somnifera for anxiety and insomnia: Systematic review and meta-analysis." Hum Psychopharmacol. 2024;39(6):e2911. PubMed