Ashwagandha: Benefits for Stress, Sleep and Hormones

Ashwagandha (Withania somnifera), also known as “Indian ginseng” or “winter cherry,” is a small evergreen shrub native to India, the Middle East, and parts of Africa. Its roots and berries have been used for millennia in Ayurveda — India’s traditional system of medicine — as a rasayana, a tonic believed to promote physical and mental health, rejuvenate the body, and increase longevity.

The name “ashwagandha” comes from Sanskrit, roughly translating to “smell of a horse,” referring both to the unique odor of its root and the traditional belief that consuming it imparts the strength and vitality of a stallion. In recent decades, ashwagandha has gained global popularity as an adaptogen — a substance that helps the body resist physical and mental stress.

This article reviews the best-available evidence for ashwagandha’s effects on stress, sleep, and hormones, providing practical guidance for safe use.

What Is Ashwagandha? An Overview

Ashwagandha belongs to the Solanaceae (nightshade) family, which also includes tomatoes, potatoes, and peppers. The most therapeutically active parts of the plant are the roots, which contain a group of bioactive compounds called withanolides — steroidal lactones that are believed to be responsible for most of its pharmacological effects.

Proposed Mechanisms

Modern research has identified several potential mechanisms through which ashwagandha may exert its effects:

• HPA axis modulation: Ashwagandha may reduce hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis, the body’s central stress response system, leading to lower cortisol production.
• GABAergic activity: Withanolides may enhance the activity of GABA (gamma-aminobutyric acid), the brain’s primary inhibitory neurotransmitter, producing calming effects similar to some sedative medications (though much milder).
• Anti-inflammatory and antioxidant effects: Ashwagandha has demonstrated the ability to reduce inflammatory markers (such as C-reactive protein, CRP) and oxidative stress in clinical trials.
• Thyroid and reproductive hormone modulation: The herb may influence the hypothalamic-pituitary-thyroid (HPT) and hypothalamic-pituitary-gonadal (HPG) axes, affecting thyroid hormone and testosterone production.

These mechanisms are supported by preclinical and some clinical data, though more research is needed to fully understand how they translate into human health outcomes.

Evidence for Stress and Anxiety

The strongest evidence for ashwagandha supports its use for reducing stress, anxiety, and cortisol levels — the body’s primary stress hormone.

1. Cortisol Reduction

A 2025 systematic review and meta-analysis of 7 randomized controlled trials (RCTs) with 488 participants found that ashwagandha supplementation significantly reduced cortisol levels compared to placebo. The mean reduction was -1.16 µg/dL (95% CI: -1.64 to -0.69, P < 0.001).

Another 2025 meta-analysis of 15 studies (873 patients) found similar results, reporting a significant reduction in cortisol at 8 weeks of treatment.

A 2024 randomized placebo-controlled study examining a highly concentrated ashwagandha extract (Shoden, standardized to 35% withanolide glycosides) found that both 60 mg and 120 mg doses significantly reduced morning serum cortisol.

2. Stress (Perceived Stress Scale)

A 2025 meta-analysis reported that ashwagandha significantly reduced perceived stress as measured by the Perceived Stress Scale (PSS), with a mean reduction of -4.88 (95% CI: -7.84 to -1.91, P = 0.0013).

However, it is important to note that not all studies have been consistent. A different 2025 meta-analysis found a statistically significant reduction in cortisol but no significant impact on perceived stress (SMD = -0.355, 95% CI: -1.188 to 0.47; P = 0.40). This discrepancy highlights the complexity of stress research and suggests that while ashwagandha reliably lowers the biological marker of stress (cortisol), its effect on subjective feelings of stress may vary depending on the population, duration of treatment, or specific product used.

3. Anxiety

The evidence for anxiety is more consistent. A 2025 meta-analysis of 15 RCTs (873 patients) found that ashwagandha significantly reduced anxiety as measured by the Hamilton Anxiety Rating Scale (HAM-A). At 8 weeks of treatment, the mean reduction was -3.52 (95% CI: -6.00 to -1.04, P = 0.0053).

Another 2025 systematic review and meta-analysis of 14 studies (713 participants) in individuals with mental disorders found strong evidence for ashwagandha’s effectiveness in treating anxiety symptoms (outlier-corrected SMD: -1.13, 95% CI: -1.65 to -0.60). The same review also found benefits for depression (SMD: -1.28, 95% CI: -2.40 to -0.16) and stress (SMD: -0.95, 95% CI: -1.46 to -0.43).

The MSD Manuals (professional edition) note that a meta-analysis of 12 RCTs comparing ashwagandha with placebo in 1,002 adults reported a statistically significant reduction in anxiety and stress, and some clinical practice guidelines have stated that daily ashwagandha root extract can be used as an adjunctive treatment in patients with generalized anxiety disorder.

Evidence for Sleep

Ashwagandha has also been studied for its effects on sleep, particularly in individuals with stress-related insomnia.

A meta-analysis of RCTs in participants with insomnia or anxiety found that ashwagandha reduced sleep latency (time to fall asleep) by 7.5 minutes, increased total sleep time by 28 minutes, and improved sleep efficiency and overall sleep quality compared to placebo.

The MSD Manuals note that a meta-analysis of randomized studies comparing ashwagandha extract capsules with placebo demonstrated small improvements in sleep quantity and quality, particularly in adults treated for more than 8 weeks.

A 2024 review on ashwagandha as an adaptogenic herb concluded that clinical trials with standardized extracts have shown reductions in stress-related biomarkers along with improvements in sleep quality and mood parameters. The review noted that ashwagandha demonstrates sleep-promoting and circadian-modulating properties.

Evidence for Hormones

Ashwagandha has been studied for its effects on several hormonal systems, with the strongest evidence for testosterone and more preliminary (and cautionary) evidence for thyroid function.

1. Testosterone and Male Fertility

Multiple studies suggest that ashwagandha may increase testosterone levels and improve sperm quality in men.

A 2025 randomized, double-blind, placebo-controlled trial in healthy male participants (aged 50–70 years) found that 200 mg of ashwagandha root extract twice daily for 180 days significantly increased testosterone levels by 15.7% compared to placebo.

A 2024 study of the Shoden extract (35% withanolide glycosides) found that both 60 mg and 120 mg doses increased total testosterone while reducing stress and anxiety.

A 2025 systematic review on reproductive health concluded that ashwagandha appears to be a promising natural adjunct for the enhancement of reproductive health. The findings indicate that ashwagandha has the potential to improve sexual health and can serve as a therapeutic agent in certain reproductive disorders due to its antioxidant nature. Other studies have shown that ashwagandha enhances sperm motility and numbers, impedes lipid peroxidation, and elevates antioxidant enzymes.

However, more research is needed to understand its long-term effects and optimal dosing fully.

2. Thyroid Function — A Cautionary Note

The evidence for ashwagandha’s effect on thyroid function is more complex and requires careful interpretation.

A 2025 safety study found that ashwagandha root extract (200 mg twice daily for 180 days) caused no adverse changes in thyroid hormone levels in healthy male participants.

However, case reports have documented thyrotoxicosis (excessively high thyroid hormone levels) associated with ashwagandha supplementation. One 8-week RCT in patients with subclinical hypothyroidism found that 300 mg of ashwagandha root extract twice daily increased thyroxine (T4) levels by 20% and decreased thyroid-stimulating hormone (TSH) by 17% compared to placebo.

In contrast, the same dose and type of extract did not affect thyroid hormones in healthy (euthyroid) individuals.

Clinical implication: Ashwagandha may have thyroid-stimulating properties. People with hyperthyroidism, Grave’s disease, or those taking thyroid hormone replacement should use ashwagandha with extreme caution and under medical supervision. Case reports suggest that in susceptible individuals, it can push thyroid hormone levels into the toxic range.

Evidence for Cognitive Function and Physical Performance

1. Cognitive Function

A 2024 review on the multifaceted effects of ashwagandha root extract found that it improved memory, attention, and anxiety and depression scores. A systematic review and meta-analysis in individuals with mental disorders also found improvements in depression symptoms. The mechanisms are thought to include antioxidant protection of brain cells, modulation of neurotransmitter systems, and reduction of stress-induced cognitive impairment.

2. Physical Performance

The same 2024 review found that ashwagandha supplementation enhanced endurance, strength, and muscle hypertrophy (growth), especially when combined with resistance training. These effects are likely mediated through reduced cortisol (catabolic hormone) and increased testosterone (anabolic hormone).

Practical Applications: How to Use Ashwagandha Safely

Choosing a Product

Ashwagandha is available in several forms:

• Root powder (traditional): The dried root ground into powder. The traditional dose is 3–6 grams daily, typically mixed into warm milk (golden milk) or water.
• Standardized extracts: The most common form in clinical trials. Look for products standardized to withanolide content (typically 2.5–10%). Common branded extracts include KSM-66 (root-only extract), Sensoril (root and leaf extract, higher withanolide content), and Shoden (ultra-high concentration, 35% withanolides).
• Liquid extracts (tinctures): Less standardized; follow product instructions.

Dosage Recommendations

General guidance: Start with a lower dose (e.g., 300 mg of KSM-66 or equivalent) and gradually increase if needed. Most clinical trials have used 8–12 week protocols. Cycling (e.g., 3 months on, 1 month off) is common in traditional practice, though evidence for this practice is limited.

Best Time to Take

Ashwagandha can be taken with or without food. For sleep support, evening dosing may be beneficial due to its mild sedative properties. For daytime stress and anxiety, morning or divided dosing is appropriate. Some people take it twice daily (morning and evening).

Comparison with Conventional Treatments

Ashwagandha is not a substitute for prescription medications in moderate to severe anxiety disorders, panic disorder, or clinical depression. It is best used for mild to moderate stress, situational anxiety, and as a supportive agent alongside lifestyle changes.

Safety, Side Effects, and Who Should Avoid Ashwagandha

Common Side Effects

Ashwagandha is generally well-tolerated. Reported side effects include:

• Mild digestive upset (nausea, diarrhea, stomach irritation)
• Headache
• Drowsiness (more common with higher doses)
• Occasional dizziness

A 2025 long-term safety study (180 days) found that 200 mg of ashwagandha root extract twice daily was well-tolerated with no adverse effects reported, and all hematological, hepatic, renal, and lipid profiles remained within normal ranges.

Serious but Rare Risks

• Liver injury: Although ashwagandha is generally considered safe from a liver perspective, there have been recent case reports of possible liver injury with elevated liver enzymes that improved with cessation of ashwagandha. A 2024 case report described a potential liver injury associated with ashwagandha use. Discontinue use and see a doctor if you develop jaundice (yellowing of skin or eyes), dark urine, or severe abdominal pain.
• Thyrotoxicosis: Case reports have documented excessively high thyroid hormone levels in people taking ashwagandha. People with thyroid disorders should use ashwagandha only under medical supervision.

Who Should Avoid Ashwagandha

• Pregnant women: Ashwagandha is contraindicated during pregnancy as it may cause uterine contractions and has been associated with abortion (pregnancy termination).
• Breastfeeding women: There is no published experience with ashwagandha during breastfeeding. It should be avoided, especially while nursing a newborn or preterm infant.
• People with hormone-sensitive cancers (prostate, breast, uterine): Ashwagandha may increase testosterone levels and should be avoided in patients with hormone-sensitive prostate cancer.
• People with hyperthyroidism or Grave’s disease: Due to the risk of thyrotoxicosis.
• People with autoimmune diseases (theoretical risk): Ashwagandha may stimulate the immune system, which could theoretically worsen conditions like rheumatoid arthritis, lupus, or multiple sclerosis. Caution advised.

Medication Interactions

• Sedatives, benzodiazepines, barbiturates: Ashwagandha may have additive sedative and GABAergic effects, potentially causing excessive drowsiness.
• Thyroid hormone replacement: Ashwagandha may have additive effects, potentially leading to thyrotoxicosis if taken with levothyroxine.
• Immunosuppressants: Theoretically, ashwagandha may reduce the effectiveness of immunosuppressive drugs.
• Diabetes medications: Ashwagandha may lower blood sugar; monitor glucose levels.
• Antihypertensives: Ashwagandha may lower blood pressure; monitor for dizziness.
• Anticonvulsants: Potential interaction due to GABAergic effects.

FAQ

Q1: How long does it take for ashwagandha to work for stress and anxiety?

Most clinical trials show measurable improvements in stress, anxiety, and cortisol levels after 4–8 weeks of consistent daily use. Some people report benefits within 2 weeks, but this varies. Do not expect immediate results.

Q2: Can ashwagandha be taken every day long-term?

A 2025 safety study showed that 200 mg twice daily for 180 days (6 months) was safe and well-tolerated with no adverse effects. However, traditional Ayurvedic practice often recommends cycling ashwagandha (e.g., 3 months on, 1 month off). Long-term safety beyond 6 months has not been well-studied. If you plan to use ashwagandha for more than 6 months, consult a healthcare provider.

Q3: Does ashwagandha interact with antidepressants?

Ashwagandha is generally considered safe with SSRIs and SNRIs, but there is a theoretical risk of additive sedation. A more significant concern is that ashwagandha may lower anxiety to the point where antidepressant doses could be reduced — but this should only be done under medical supervision. Do not stop or reduce antidepressant medications on your own.

Q4: Is ashwagandha safe for women? Does it affect female hormones?

Ashwagandha is safe for most women when used appropriately. Some studies suggest it may help balance hormones in perimenopause. However, pregnant women should avoid it entirely. Women with hormone-sensitive conditions (e.g., breast cancer, uterine fibroids, endometriosis) should consult a doctor before use. Ashwagandha is generally considered safe during breastfeeding, though formal safety studies are lacking, and it is best avoided in nursing newborns.

Q5: Can ashwagandha help with thyroid problems?

Ashwagandha has shown potential to increase thyroid hormone levels in people with subclinical hypothyroidism. However, case reports have documented thyrotoxicosis (dangerously high thyroid hormone levels) in some individuals. Do not use ashwagandha to self-treat hypothyroidism. If you have a thyroid disorder, consult your endocrinologist before taking ashwagandha. People with hyperthyroidism or Grave’s disease should generally avoid it.

Q6: What is the difference between KSM-66, Sensoril, and Shoden?

• KSM-66: A root-only extract, standardized to 5% withanolides. Most researched for stress, anxiety, and physical performance. Good for daytime use.
• Sensoril: A root-and-leaf extract, standardized to 10% withanolides. Higher potency; often used for sleep support.
• Shoden: An ultra-high-concentration extract, standardized to 35% withanolides. Most potent; clinical trials used 60–120 mg doses.

All three are effective; choose based on your goals and budget. KSM-66 has the most published research.

Key Takeaways

• Ashwagandha has the strongest evidence for reducing stress, anxiety, and cortisol levels, with meta-analyses showing statistically significant benefits after 8 weeks of treatment.
• It may improve sleep quality by reducing sleep latency (by about 7.5 minutes) and increasing total sleep time (by about 28 minutes).
• Evidence supports modest increases in testosterone and improvements in sperm quality in men, but more research is needed on long-term effects.
• Caution: Ashwagandha may stimulate thyroid function and has been associated with thyrotoxicosis in case reports. People with hyperthyroidism should avoid it; those with hypothyroidism should use it only under medical supervision.
• Rare but serious risks include liver injury and, during pregnancy, potential uterine stimulation. Pregnant women should avoid ashwagandha entirely.
• Ashwagandha is not a substitute for prescription medications for moderate to severe anxiety disorders, panic disorder, or clinical depression.
• If you choose to take ashwagandha, use standardized extracts from reputable manufacturers, start with a low dose (e.g., 300 mg of KSM-66), and discontinue use if you experience jaundice, dark urine, or symptoms of hyperthyroidism (racing heart, heat intolerance, unexplained weight loss).

Internal Links Used

1. Adaptogens: ancient herbs for modern stress — in the introduction, as ashwagandha is a key adaptogen
2. Natural remedies for anxiety without medication — in the anxiety section, for readers seeking other natural approaches to anxiety
3. Herbal teas that help you sleep better — in the sleep section, for readers interested in other natural sleep aids
4. How to detox your liver naturally with herbs — in the liver injury safety section
5. Adaptogens: ancient herbs for modern stress – in the introduction (already there)
   Add: Natural remedies for anxiety without medication – in the anxiety section
6. Medicinal mushrooms: lion’s mane, reishi and chaga – in the sleep section
7. CBD oil: benefits, risks and what doctors think – in the hormone section

Sources

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7. Roy, D., et al. “Effects of Ashwagandha on Reproductive Health: A Systematic Review of Sex-Specific Hormonal and Fertility Outcomes.” Phytotherapy Research. 2025. 
8. “Safety and Tolerability of Withania somnifera Root Extract in Healthy Male Participants: A Pilot Randomized, Double‐Blind, Placebo‐Controlled Clinical Trial.” Food Science & Nutrition. 2025;14(1):e71388. 
9. “What’s the story with ashwagandha for hypothyroidism?” Examine.com. May 16, 2025. 
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