Ashwagandha does appear to improve sleep, and the evidence is stronger than for many herbal supplements. A meta-analysis published in PLOS One found that ashwagandha extract significantly improved sleep onset latency, sleep quality, and mental alertness upon waking compared to placebo. In one clinical trial, 72% of participants taking ashwagandha reported improved sleep quality, compared to just 29% in the placebo group.
What the Clinical Evidence Shows
Several randomized controlled trials have tested ashwagandha against placebo for sleep, and the results are consistently positive across multiple sleep measures. Participants taking ashwagandha showed improvements in sleep efficiency (the percentage of time in bed actually spent sleeping), total sleep time, how quickly they fell asleep, and how often they woke up during the night. These weren’t just self-reported improvements. Some studies used actigraphy, a wrist-worn device that objectively tracks sleep and wake patterns, confirming that the benefits were measurable and not just perceived.
The NIH’s Office of Dietary Supplements reviewed the available research and concluded that ashwagandha extract “may improve several aspects of sleep, including sleep quality, sleep efficiency, total sleep time, and sleep latency.” That’s a cautious endorsement, reflecting the fact that while the evidence is promising, the total number of studies is still relatively small.
How Ashwagandha Affects the Brain During Sleep
Ashwagandha promotes sleep through at least two pathways in the brain. First, it increases levels of GABA, the brain’s primary calming neurotransmitter. GABA slows down nerve activity and is the same system targeted by many prescription sleep medications. Research shows ashwagandha boosts GABA content in the brain and changes how GABA receptors are expressed, making the brain more responsive to this calming signal.
Second, ashwagandha activates adenosine receptors. Adenosine is the molecule that builds up in your brain throughout the day and creates “sleep pressure,” that increasing feeling of sleepiness the longer you’ve been awake. It’s also the molecule that caffeine blocks to keep you alert. By enhancing adenosine signaling, ashwagandha essentially amplifies your body’s natural drive to sleep.
Beyond these direct sleep pathways, ashwagandha also influences genes related to serotonin signaling and lowers cortisol levels. Multiple trials have found that participants taking ashwagandha had measurably lower cortisol, the body’s main stress hormone. Since stress and racing thoughts are among the most common reasons people can’t fall asleep, this cortisol-lowering effect likely contributes to the overall sleep benefit, especially for people whose poor sleep is driven by anxiety or tension.
How Long It Takes to Work
Don’t expect results the first night. Ashwagandha is not a sedative that knocks you out like a sleeping pill. Most clinical trials run for six weeks or longer before measuring outcomes, and that appears to be a reasonable timeline to expect noticeable changes. In one six-week randomized trial of 150 adults with sleep disturbances, participants taking 120 mg of ashwagandha extract showed improvements in how quickly they fell asleep, how long they stayed asleep, sleep efficiency, and nighttime wakefulness by the end of the study period. Other trials have run for 8 to 12 weeks with similarly positive results.
The benefit seems to build gradually as ashwagandha modulates brain chemistry over time, particularly by increasing GABA levels and adjusting receptor expression. If you’ve been taking it for two weeks with no change, that’s expected. Give it at least six weeks of consistent daily use before deciding whether it’s working for you.
Dosage and Extract Types
The doses used in clinical trials vary quite a bit depending on the type of extract, which matters because different extracts concentrate the active compounds differently. Studies have used doses as low as 120 mg of highly concentrated extracts and as high as 600 mg of root extracts. One trial found that even a 225 mg dose was enough to lower cortisol levels compared to placebo. Most supplements on the market use standardized root extracts in the 300 to 600 mg range, taken once or twice daily, which aligns with the dosing in successful trials.
Look for products that specify they use a standardized extract and list the concentration of withanolides, the active compounds in ashwagandha. The specific extract brand matters less than knowing what concentration you’re actually getting, since unstandardized products can vary widely in potency.
Side Effects and Safety Concerns
For most people, ashwagandha is well tolerated in the short to medium term. The clinical trials lasting 6 to 12 weeks generally report mild or no side effects. However, there are some real safety concerns worth knowing about.
Rare cases of liver injury have been documented. A case series from Iceland identified five patients, and additional cases have been reported in Japan and elsewhere. None required a liver transplant, and liver function typically returned to normal within about three and a half months after stopping the supplement. The toxicity appeared to be dose-dependent, with higher doses linked to more severe effects. These cases are uncommon, but they’re a reason to stick to recommended doses and not assume that more is better.
Ashwagandha can also interact with several categories of medications:
- Sedatives and sleep medications: Ashwagandha may amplify their effects, leading to excessive drowsiness
- Thyroid medications: It can increase thyroid hormone levels, potentially throwing off a carefully calibrated dose
- Blood sugar medications: It may lower blood glucose further than intended
- Blood pressure medications: It can enhance their blood pressure-lowering effects
- Immunosuppressants: Ashwagandha may stimulate immune activity, counteracting drugs designed to suppress it
Who Should Avoid It
The National Center for Complementary and Integrative Health specifically recommends against ashwagandha for people with autoimmune disorders, thyroid conditions, or those about to have surgery. Because ashwagandha can increase testosterone levels, people with hormone-sensitive prostate cancer should also avoid it. It should not be used during pregnancy or while breastfeeding.
If you’re taking any of the medication categories listed above, the interaction risk is real enough to warrant a conversation with your pharmacist or prescriber before adding ashwagandha to your routine. This is especially true for sedatives, since combining two substances that both enhance GABA activity can produce unpredictable levels of sedation.
How It Compares to Other Sleep Aids
Ashwagandha occupies a different niche than most sleep supplements. Melatonin, for instance, works by signaling to your brain that it’s nighttime, primarily helping with circadian rhythm issues like jet lag or delayed sleep phase. Ashwagandha works through entirely different mechanisms: calming the nervous system via GABA, enhancing sleep pressure via adenosine, and reducing the stress hormones that keep you wired at night.
This makes ashwagandha potentially more useful for people whose sleep problems are tied to stress, anxiety, or an overactive mind at bedtime, rather than a shifted internal clock. It also means ashwagandha and melatonin target different problems and aren’t directly interchangeable. The tradeoff is speed: melatonin works the same night you take it, while ashwagandha requires weeks of consistent use to reach its full effect.