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Ashwagandha for Stress and Sleep: What Clinical Trials Actually Show

November 1, 2026 · Researched and written with AI.

Ashwagandha (Withania somnifera) is one of the most widely used adaptogenic herbs in traditional wellness practices. In recent years, researchers have conducted numerous clinical trials to evaluate how standardized extracts affect everyday stress, anxiety, sleep quality, and physiological markers like serum cortisol. With a significant body of literature synthesized through 2026, systematic reviews offer a clear picture of what the clinical evidence shows.

What Clinical Trials Show for Stress and Anxiety

Multiple randomized controlled trials (RCTs) show that ashwagandha extracts can help reduce self-reported stress and anxiety scores. A 2026 systematic review analyzing clinical trial data found that ashwagandha demonstrated efficacy for anxiety across 10 RCTs and for stress across 8 RCTs, typically testing doses between 30 and 600 milligrams per day of standardized withanolide extract. A separate 2026 meta-analysis pooling 22 clinical studies reported significant statistical reductions in measured levels of stress, anxiety, and low mood among adult participants.

Individual clinical trials offer specific details on how these stress reductions present:

Healthy adults with moderate stress: An 8-week trial involving 141 healthy adults evaluated 300 milligrams of ashwagandha root extract taken twice daily. Participants receiving the extract showed significant reductions in serum cortisol as well as lower scores on the Perceived Stress Scale (PSS) and Hamilton Anxiety Rating Scale (HAM-A) compared to placebo.
Multi-herb comparison: A 60-day trial with 186 adults suffering from high stress evaluated a full-spectrum ashwagandha extract against placebo. Supplementation was associated with reductions in perceived stress, fatigue, and anxiety alongside improvements in mood.
Lower daily dosing: An 84-day trial in 90 adults with mild to moderate stress found that a 125-milligram daily dose of standardized ashwagandha extract lowered Perceived Stress Scale scores, anxiety symptoms, and sleep quality scores relative to placebo.
Stress with cardiometabolic factors: A 60-day trial in 60 adults managing stress alongside pre-existing hypertension tested 300 milligrams of standardized extract twice daily. Participants in the ashwagandha group experienced a 30.47% drop in perceived stress scores, a 26.94% reduction on the Hamilton Anxiety scale, a 50.77% reduction on Generalized Anxiety Disorder (GAD-7) scores, and a 13.00% drop in blood triglycerides.

Sleep Quality and Fatigue

Shoppers frequently look to ashwagandha for evening relaxation and sleep support. Clinical trials indicate that improvements in sleep quality frequently accompany stress reduction.

In systematic review data, ashwagandha demonstrated positive effects on sleep outcomes across 3 randomized controlled trials. In studies measuring standardized sleep questionnaires, such as the Pittsburgh Sleep Quality Index (PSQI), participants taking ashwagandha reported better sleep quality, less fatigue, and more restorative sleep than those taking a placebo. However, researchers note that the total number of clinical trials focused primarily on sleep remains small compared to those evaluating stress and anxiety.

Biological Impact: Cortisol and Other Hormones

To understand how ashwagandha exerts its adaptogenic effects, researchers measure physiological markers of the hypothalamic-pituitary-adrenal (HPA) axis, which governs the body's stress response. Serum cortisol—a major stress hormone—is frequently evaluated.

A 2026 systematic review calculated a pooled cortisol reduction of -3.27 micrograms per deciliter (-3.27 µg/dL) across clinical trials. In addition, a comprehensive meta-analysis of 23 randomized placebo-controlled trials encompassing 1,706 adults evaluated systemic hormonal changes following oral ashwagandha supplementation. The meta-analysis confirmed a statistically significant reduction in cortisol alongside an average increase in circulating serotonin of 31.75 nanograms per milliliter (ng/mL).

The same 23-trial meta-analysis and a related 2026 endocrinology review evaluated other hormonal pathways:

Thyroid Function: Supplementation showed no significant effect on thyroid-stimulating hormone (TSH) or triiodothyronine (T3), but resulted in a modest increase in thyroxine (T4) levels (a mean difference of 0.61 µg/dL). Reviews note that ashwagandha appears to elevate thyroid hormones in hypothyroid contexts.
Sex Hormones: Supplementation significantly increased serum testosterone in men (a mean difference of 57.43 ng/dL), but did not cause a significant change in testosterone for women (5.09 ng/dL). Estradiol levels were not significantly affected in either group.

Study Quality and Research Gaps

While these clinical findings are positive, systematic reviewers emphasize several study limitations:

Methodology concerns: In a 31-trial systematic review, only 10 trials were rated as having a low risk of bias, while the remainder raised some methodology concerns. Overall certainty of evidence using standard GRADE criteria was rated as moderate at best.
Heterogeneity: Meta-analyses report high statistical heterogeneity across trials due to variations in extract processing, withanolide concentrations, daily dosages, and trial lengths.
Unstudied conditions: Systematic reviewers emphasize that no randomized controlled trials exist for severe stress-related conditions such as clinical burnout or posttraumatic stress disorder (PTSD), despite preclinical research on those mechanisms.

Safety, Side Effects, and Precautions

In short- to medium-term clinical trials lasting between 30 and 84 days, ashwagandha was generally well tolerated with low rates of adverse events. However, safety researchers highlight key precautions for extended use:

Liver function: Systematic reviews note that ashwagandha-associated hepatotoxicity (liver injury) has been reported, suggesting liver enzyme monitoring may be prudent during prolonged use.
Thyroid and blood pressure interactions: Because ashwagandha can modestly increase T4 thyroid hormone levels and lower cortisol and blood pressure, it may interact with prescription treatments.

Always talk to your doctor or pharmacist before starting ashwagandha, particularly if you take prescription medications (such as thyroid or blood pressure drugs), are pregnant or breastfeeding, or have an underlying liver or endocrine condition.

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Sources

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