Ashwagandha (Withania somnifera) — an Ayurvedic adaptogen — has accumulated RCT evidence for sleep specifically through its cortisol-lowering and GABA-modulating properties, making it particularly effective for stress-disrupted sleep rather than simple insomnia.
What Does the Research Say?
The most rigorous ashwagandha sleep trial to date — a 2019 RCT published in PLOS ONE (n=60) — found 300mg KSM-66 ashwagandha extract twice daily for 10 weeks significantly improved sleep quality (PSQI score), sleep onset latency, sleep efficiency, and non-restorative sleep compared to placebo. Salivary cortisol levels dropped significantly in the supplemented group — the likely primary mechanism given cortisol’s role in suppressing deep sleep stages.
A 2020 double-blind RCT specifically in adults with non-restorative sleep found 120mg ashwagandha extract (Shoden, 35% withanolide glycosides) for 6 weeks significantly improved total sleep time, sleep quality, mental alertness on waking, and daytime sleepiness. Animal studies show withanolides (ashwagandha’s bioactive compounds) bind GABA receptors directly — a mechanism that bridges its anxiolytic and sleep-promoting effects. Ashwagandha’s benefits are most pronounced in individuals with elevated stress and anxiety, where HPA axis dysregulation is the primary sleep disruptor.
Key Findings
- RCT: 300mg KSM-66 daily for 10 weeks significantly improved PSQI sleep score and reduced cortisol
- Second RCT confirms improved total sleep time, quality, and next-day alertness with Shoden extract
- Withanolides bind GABA receptors — providing direct neurological sleepiness promotion beyond cortisol effects
- Most effective in stress-disrupted sleep; effect size larger in individuals with high baseline anxiety
Practical Takeaway
Use standardized extracts: KSM-66 or Shoden brands have the strongest clinical evidence. Dose: 300–600mg daily, taken in evening or split morning/evening. Allow 4–8 weeks for full effect as adaptogens work cumulatively. Do not use during pregnancy. Find ashwagandha: ashwagandha supplements.