Nmn And Memory Preservation
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Ashwagandha is a plant root that may help improve sleep by lowering cortisol, your body’s stress hormone. When cortisol stays high in the evening, your brain stays alert and sleep becomes difficult. Research shows ashwagandha works by helping your stress system calm down rather than forcing drowsiness, which is a healthier mechanism for your brain.
Multiple clinical trials found that ashwagandha meaningfully reduced cortisol levels and improved sleep quality, particularly in people with insomnia. The most pronounced improvements appeared with doses of 300 to 600 mg daily over at least eight weeks. A standardised extract containing higher withanolide content (the active compound) may work better than taking higher amounts of a weaker formulation. Anxiety also improved in several studies, which matters because anxiety and poor sleep feed each other.
The short-term safety record is excellent with no serious side effects reported across studies. However, long-term safety data beyond 12 weeks is limited. If you take thyroid medication or hormone therapy, mention ashwagandha to your doctor, though no documented harm exists. The research is genuinely promising but comes from small studies, so this is a reasonable low-risk option to try rather than a proven cure.
Verdict: Ashwagandha shows consistent, modest-to-meaningful benefits for sleep and stress in clinical trials, making it a reasonable low-risk option for people struggling with poor sleep and chronic stress, though it works best as part of a broader approach to managing stress itself.
What if the reason you can’t sleep properly has nothing to do with your bedtime routine, your phone screen, or your mattress? What if the real culprit is a stress hormone quietly misfiring in your body for hours before you even try to close your eyes, and what if a well-researched botanical could help reset it?
Cortisol is your body’s primary stress hormone. In a healthy system, it follows a graceful arc: high in the morning to wake you up, gradually declining throughout the day, and low by night so your brain can shift into sleep mode. But modern life has a habit of keeping that arc flattened, or worse, spiking it at exactly the wrong time. The result isn’t just poor sleep. It’s a cascade of downstream effects on mood, memory, and long-term brain health that researchers are only beginning to fully map.
This is where ashwagandha, a root used in Ayurvedic medicine for centuries, has attracted serious scientific attention. Not as a sedative. Not as a quick fix. But as what researchers call an *adaptogen*: something that appears to help your body regulate its own stress response rather than simply overriding it. The research here is genuinely interesting. Vitacuity analysed over 1.77 million research papers and selected the most relevant studies on this topic to bring you a clear, honest picture of what we actually know.
To understand why ashwagandha might improve sleep, you need to understand the system it appears to target: the hypothalamic-pituitary-adrenal (HPA) axis. Think of this as your body’s stress command centre. When your brain perceives a threat, whether real or imagined, physical or psychological, it sends a signal down this chain that ends with your adrenal glands releasing cortisol [2].
In small, timely doses, cortisol is your friend. It sharpens attention, mobilises energy, and prepares your body to respond. But when the HPA axis is chronically activated, as it is for many adults navigating work pressure, financial worry, or even the low-level anxiety of modern life, cortisol stops following its natural rhythm. Evening cortisol stays elevated. Your brain, reading this chemical signal as “danger is still present,” delays or disrupts the sleep initiation process [13].
Ashwagandha’s active compounds, primarily a group called withanolides, appear to modulate this system rather than suppress it outright. Research suggests they act on the HPA axis centrally, reducing the signalling that triggers cortisol release [2]. This is mechanistically different from taking a sleeping tablet, which forces sedation regardless of what your stress system is doing. Ashwagandha appears to work upstream.
There’s a second pathway, too. Animal studies, and some preliminary human research, suggest ashwagandha may interact with GABA receptors in the brain [14]. GABA is the nervous system’s primary “calm down” neurotransmitter. It’s the same system targeted by many pharmaceutical sleep aids. In a 2023 study using an enzyme-treated ashwagandha extract, researchers found dose-dependent increases in sleep duration in rodent models, along with increases in GABA content in the brain and enhanced expression of GABA receptors. Critically, this treatment also increased delta-wave (deep, restorative) sleep as confirmed by electroencephalogram analysis [14]. Worth noting: this is animal research, so we should treat it as mechanism-building rather than proof in humans.
The most robust finding across multiple studies is that ashwagandha appears to lower serum cortisol in stressed adults. A 2019 randomised, double-blind, placebo-controlled trial published in *Cureus* tested two doses, 250 mg/day and 600 mg/day, against placebo over eight weeks in 60 stressed healthy adults. Serum cortisol was significantly reduced in both the 250 mg group (p < 0.05) and the 600 mg group (p < 0.0001) compared to placebo [6].
A second 2019 randomised, double-blind, placebo-controlled study published in *Medicine* (n = 60 stressed adults, 60 days) found significant reductions in morning cortisol in the ashwagandha group (240 mg of a standardised extract, Shoden) compared to placebo (p < 0.001) [11]. This is meaningful because morning cortisol is both easier to measure accurately and a strong indicator of overall HPA axis activity.
A 2022 study published in the *Journal of Ayurveda and Integrative Medicine* tested 225 mg/day and 400 mg/day in 60 adults with perceived stress over 30 days. Both ashwagandha groups showed reductions in cortisol over time, with the 225 mg group reaching statistical significance from Day 0 to Day 30. The placebo group, by contrast, showed a non-significant *increase* in cortisol over the same period [7].
However, and this is important, a 2025 systematic review and meta-analysis published in *Nutrition & Food Science* found something intriguing: ashwagandha produced significant cortisol reductions on biological measurement, but this didn’t always translate into equivalent reductions in *perceived stress* scores [5]. So the hormone changes are real, but whether people *feel* less stressed is a more complicated picture. We’ll return to this below.
Evidence grade: Promising to Strong. Cortisol reduction has been demonstrated across multiple RCTs with consistent direction, though sample sizes are generally small (under 100 per trial) and study durations short.
A 2021 systematic review and meta-analysis published in *PLOS ONE* pooled data from five randomised controlled trials covering 400 participants and found that ashwagandha extract produced a small but statistically significant improvement in overall sleep quality (Standardised Mean Difference: -0.59; 95% CI: -0.75 to -0.42) [8]. The effects were more pronounced in people with diagnosed insomnia compared to healthy sleepers, and stronger at doses of 600 mg/day or more for durations of eight weeks or longer [8].
A 2021 study published in the *Journal of Ethnopharmacology* examined 80 participants, 40 healthy and 40 with insomnia, in a randomised, double-blind, placebo-controlled design over eight weeks. In the insomnia group, ashwagandha significantly improved sleep onset latency (the time it takes to fall asleep), total sleep time, wake after sleep onset, sleep efficiency, and sleep quality scores (all p < 0.0001 compared to baseline). Sleep onset latency and sleep efficiency showed the most dramatic improvements. The healthy group also benefited, though more modestly [10].
A 2019 randomised, double-blind, placebo-controlled study published in *Cureus* (n = 60 insomnia patients, 10 weeks, 300 mg twice daily) confirmed these findings using objective actigraphy, wrist-worn devices that track actual sleep movements, not just self-report. Sleep onset latency was significantly shorter after 10 weeks in the ashwagandha group (29.00 minutes) versus placebo (33.94 minutes) (p = 0.019). Sleep efficiency improved from 75.63% at baseline to 83.48% at 10 weeks for the ashwagandha group, compared to 75.14% to 79.68% in the placebo group [15].
Beyond the numbers: participants also reported significant improvements in mental alertness on rising, which matters enormously for how we actually function the next day [10][15].
Evidence grade: Promising. Multiple RCTs show consistent improvements in sleep quality, onset and efficiency. Meta-analysis confirms the direction of effect. But most studies have under 100 participants, and we lack long-term safety data beyond 12 weeks.
It would be a mistake to treat cortisol, anxiety and sleep as separate issues. They are deeply intertwined. Anxiety keeps the HPA axis activated. Elevated evening cortisol maintains anxiety-like arousal states. Poor sleep raises cortisol the following day. It’s a loop, and breaking it at any point tends to have knock-on benefits.
Ashwagandha appears to have genuine anxiolytic (anti-anxiety) effects. The 2019 *Cureus* dose-response study found significant reductions in Perceived Stress Scale (PSS) scores, at 250 mg/day (p < 0.05) and 600 mg/day (p < 0.001), alongside the cortisol reductions [6]. The 2019 *Medicine* study found significant improvements in the Hamilton Anxiety Rating Scale (HAM-A) (p = 0.040) with 240 mg daily [11].
More recently, a 2025 randomised, double-blind, placebo-controlled trial published in *Advances in Therapy* (n = 90, 84 days) tested an unusually low dose, just 125 mg daily of a high-withanolide formulation (Zenroot™). Despite the lower dose, it produced significant improvements in Perceived Stress Scale scores, Beck Anxiety Inventory scores, and Pittsburgh Sleep Quality Index scores from Day 28 onwards (p < 0.05) [1]. It also improved objective heart rate variability measures, a physiological marker of nervous system regulation, within just 14 days [1]. Notably, this study found no significant effect on serum cortisol itself, reinforcing the point from the 2025 meta-analysis [5] that the relationship between cortisol reduction and subjective wellbeing is not always linear.
Evidence grade: Promising. Multiple RCTs support anxiolytic effects across a range of doses. The consistency of direction is encouraging, though samples remain small and mostly short-term.
One of the genuinely surprising things to emerge from the ashwagandha literature is that dose response doesn’t always work the way you’d expect. Higher is not automatically better.
The 2019 *Cureus* study showed benefits at both 250 mg/day and 600 mg/day, with stronger cortisol effects at the higher dose [6]. But the 2022 cognition study found significant cortisol reductions at 225 mg/day, while the 400 mg group showed a trend that didn’t reach significance [7]. And the 2025 Zenroot study found meaningful sleep and anxiety improvements at just 125 mg/day of a concentrated extract standardised to 1.5% withanolides [1].
This suggests that the withanolide content of the extract, the standardised concentration of active compounds, may matter more than the raw weight of the dose. A lower-milligram, higher-potency extract may outperform a higher-milligram, lower-potency one. The 2021 review published in *Current Neuropharmacology* noted that “significant variability in the WS extracts examined prevents a consensus on the optimum WS preparation or dosage” [13], which is honest and accurate. The 2025 *Phytotherapy Research* review echoed this, noting that limitations in existing studies include high variability in formulations [2].
Evidence grade: Conflicted, not because the ingredient doesn’t work, but because the optimal dose and extract type remain genuinely unclear. What the research suggests is that looking for standardised withanolide content (typically 1.5–5%) matters more than simply buying the highest milligram count on the label.
Chronic cortisol elevation isn’t just bad for sleep. Sustained high cortisol is associated with impaired memory, reduced cognitive flexibility, and accelerated brain ageing, which is why ashwagandha’s cognitive findings are relevant here.
The 2022 study published in the *Journal of Ayurveda and Integrative Medicine* found that ashwagandha groups significantly outperformed placebo on measures of cognitive flexibility, visual memory, reaction time, psychomotor speed, and executive functioning over 30 days (p < 0.05) [7]. The researchers noted that both ashwagandha groups often outperformed placebo even when self-reported stress measures weren’t always significantly different between groups, suggesting direct cognitive effects beyond simply feeling calmer [7].
A 2021 comprehensive review published in *Current Neuropharmacology* summarised that ashwagandha’s neuropsychiatric benefits appear to work through multiple pathways simultaneously: HPA axis modulation, sympathetic nervous system regulation, GABAergic activity, and serotonergic pathways [13]. This multi-pathway action is characteristic of adaptogens and may explain why the benefits seem to be spread across mood, sleep, and cognition rather than isolated to one domain.
Evidence grade: Early to Promising for cognitive effects specifically. Most cognitive data comes from small, short trials. It’s consistent in direction but needs larger, longer-term studies to confirm.
Honesty matters here, because ashwagandha has attracted enough hype that it’s worth being precise about where the evidence runs out.
The cortisol-stress disconnect. The 2025 meta-analysis found that ashwagandha reliably lowers measured cortisol, but doesn’t always produce equivalent improvements in perceived stress [5]. This is genuinely puzzling. It could mean that psychological stress involves more than cortisol alone; it could reflect placebo effects inflating self-report measures in some studies; or it could mean cortisol reduction matters biochemically even when people don’t notice it subjectively. We don’t know.
Long-term safety. Almost all the human RCTs run for eight to twelve weeks. The 2021 meta-analysis noted that “data on serious adverse effects of ashwagandha extract are limited, and more safety data would be needed to assess whether it would be safe for long-term use” [8]. The 2023 systematic review published in *Nutrients* added that none of the studies evaluated whether cortisol reduction could affect adrenal function over the long term [12]. This is not a reason for alarm, short-term studies show a consistently excellent safety profile, but it is a genuine knowledge gap.
Hormonal effects need monitoring. The 2025 *Phytotherapy Research* review flagged that ashwagandha may influence thyroid hormones, testosterone in men, and oestrogen and gonadotrophins in women, likely through central HPA and HPG axis modulation rather than direct receptor binding [2]. For most healthy adults taking normal doses, this is probably a feature rather than a bug. But for people with thyroid conditions or those on hormone-related medications, this warrants attention and ideally professional guidance.
Who benefits most? The meta-analysis found effects were more pronounced in people with diagnosed insomnia [8]. Whether ashwagandha produces meaningful sleep benefits in people who already sleep reasonably well is less clear.
Extract standardisation. The variability in formulations across studies makes direct comparison difficult. Without knowing the withanolide content of a given product, it’s genuinely hard to translate a dose from a study into a practical recommendation [13].
The GABA mechanism in humans. The GABA receptor evidence is interesting but comes primarily from rodent models [14]. We don’t yet have clean human mechanistic data confirming this pathway operates the same way in people.
Let’s be practical about this. The research picture for ashwagandha and sleep is not “proven miracle herb”, but it’s also not “insufficient evidence, see your doctor.” It sits somewhere more interesting: a genuinely promising adaptogen with multiple RCTs showing consistent, modest-to-meaningful effects on cortisol regulation, sleep quality, sleep onset latency, and anxiety, with an excellent short-term safety record.
Here’s how a sensible, informed person might think about this:
If you sleep poorly and feel chronically stressed, the research suggests ashwagandha is a reasonable, low-risk intervention worth trying. The effects in insomnia patients are more pronounced than in healthy sleepers [8], which makes intuitive sense given the cortisol-sleep connection. Give it at least eight weeks, shorter trials show less robust results [8].
On dosing, look for a standardised extract rather than raw powder. The research spans 125 mg of high-withanolide extract to 600 mg of standard extract. If you’re using a concentrated, standardised product (1.5% withanolides or higher), the evidence suggests even lower milligram doses can be effective [1]. If using a standard extract, 300–600 mg daily appears to be the range with the strongest sleep-specific evidence [10][15][8].
Timing matters. Several researchers suggest evening dosing makes intuitive sense given the goal of lowering evening cortisol, though head-to-head dosing-time comparisons haven’t been done in the human literature reviewed here.
It’s not a sedative. This distinction matters. Ashwagandha doesn’t knock you out. It appears to work by helping your stress system settle down so that natural sleep can occur. That’s actually a better mechanism for brain health over the long term than forcing sedation.
Safety: In all the trials reviewed here, ashwagandha was consistently well tolerated with no serious adverse events [1][6][8][10][11][15]. At normal supplement doses, it appears to be a genuinely low-risk intervention. If you’re on thyroid medication, hormone therapy, or immunosuppressants, it’s worth flagging to your GP simply because of the hormonal modulation pathway, not because there’s documented harm, but because the research on interactions is limited [2].
The practical bottom line: Chronic stress is a real, measurable threat to sleep quality and long-term cognitive health. Ashwagandha has more good human evidence behind it than most herbal supplements, multiple double-blind, placebo-controlled trials, a meta-analysis confirming the sleep direction of effect, and consistent cortisol data. It’s not a substitute for addressing the sources of stress in your life. But as part of a serious approach to protecting your brain as you age, it earns its place.
[1] A New Ashwagandha Formulation (Zenroot™) Alleviates Stress and Anxiety Symptoms While Improving Mood and Sleep Quality: A Randomized, Double-Blind, Placebo-Controlled Clinical Study. (2025). *Advances in Therapy*. DOI: 10.1007/s12325-025-03327-z | https://pubmed.ncbi.nlm.nih.gov/40875185/ | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12474591/
[2] Evaluation of Potential Hormonal Activities of Ashwagandha (Withania somnifera). (2025). *Phytotherapy Research*. DOI: 10.1002/ptr.70155 | https://pubmed.ncbi.nlm.nih.gov/41454558/
[3] Withania somnifera (Ashwagandha) supplementation: a review of its mechanisms, health benefits, and role in sports performance. (2025). *Nutrition & Metabolism*. DOI: 10.1186/s12986-025-00902-7 | https://pubmed.ncbi.nlm.nih.gov/39910586/ | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11800443/
[4] Ashwagandha (Withania somnifera) and mental health, cognitive function, sleep quality and related outcomes. (2025). *Nutrients*. DOI: 10.3390/nu17132143 | https://pubmed.ncbi.nlm.nih.gov/40647248/ | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12252077/
[5] Dual impact of Ashwagandha: Significant cortisol reduction but no effects on perceived stress, A systematic review and meta-analysis. (2025). *Nutrition & Food Science*. DOI: 10.1177/02601060251363647 | https://pubmed.ncbi.nlm.nih.gov/40746175/
[6] Adaptogenic and Anxiolytic Effects of Ashwagandha Root Extract in Healthy Adults: A Double-blind, Randomized, Placebo-controlled Clinical Study. (2019). *Cureus*. DOI: 10.7759/cureus.6466 | https://pubmed.ncbi.nlm.nih.gov/32021735/ | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6979308/
[7] Efficacy of Withania somnifera supplementation on adult’s cognition and mood. (2022). *Journal of Ayurveda and Integrative Medicine*. DOI: 10.1016/j.jaim.2021.08.003 | https://pubmed.ncbi.nlm.nih.gov/34838432/ | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8728079/
[8] Effect of Ashwagandha (Withania somnifera) extract on sleep: A systematic review and meta-analysis. (2021). *PLOS ONE*. DOI: 10.1371/journal.pone.0257843 | https://pubmed.ncbi.nlm.nih.gov/34559859/ | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8462692/
[10] Clinical evaluation of the pharmacological impact of ashwagandha root extract on sleep in healthy volunteers and insomnia patients: A double-blind, randomized, parallel-group, placebo-controlled study. (2021). *Journal of Ethnopharmacology*. DOI: 10.1016/j.jep.2020.113276 | https://pubmed.ncbi.nlm.nih.gov/32818573/
[11] An investigation into the stress-relieving and pharmacological actions of an ashwagandha (Withania somnifera) extract: A randomized, double-blind, placebo-controlled study. (2019). *Medicine*. DOI: 10.1097/MD.0000000000017186 | https://pubmed.ncbi.nlm.nih.gov/31517876/ | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6750292/
[12] Effects of Withania somnifera on cortisol levels in stressed humans: A systematic review. (2023). *Nutrients*. DOI: 10.3390/nu15245015 | https://pubmed.ncbi.nlm.nih.gov/38140274/ | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10745833/
[13] Effects of Withania somnifera (Ashwagandha) on stress and the neurobiology of anxiety and depression. (2021). *Current Neuropharmacology*. DOI: 10.2174/1570159X19666210712151556 | https://pubmed.ncbi.nlm.nih.gov/34254920/ | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8762185/
[14] Sleep-promoting activity of amylase-treated Ashwagandha (Withania somnifera L. Dunal) root extract via GABA receptors. (2023). *Journal of Microbiology and Biotechnology*. DOI: 10.38212/2224-6614.3456 | https://pubmed.ncbi.nlm.nih.gov/37335157/ | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10281725/
[15] Efficacy and Safety of Ashwagandha (Withania somnifera) Root Extract in Insomnia and Anxiety: A Double-blind, Randomized, Placebo-controlled Study. (2019). *Cureus*. DOI: 10.7759/cureus.5797 | https://pubmed.ncbi.nlm.nih.gov/31728244/ | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6827862/
This article is for informational purposes only and does not constitute medical advice. Food supplements should not be used as a substitute for a varied and balanced diet and healthy lifestyle. If you are pregnant, breastfeeding, taking medication or have a medical condition, consult your doctor before taking any supplement. These statements have not been evaluated by the Food and Drug Administration (FDA) or the Medicines and Healthcare products Regulatory Agency (MHRA). This product is not intended to diagnose, treat, cure, or prevent any disease.
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