Ashwagandha for stress and anxiety: the evidence and the cautions

Short answer: Some clinical trials suggest ashwagandha extracts may reduce perceived stress and lower cortisol levels, but the NIH Office of Dietary Supplements grades this evidence as limited, not strong. Several safety cautions, especially around liver function, thyroid medications, and pregnancy, mean it is worth discussing with a clinician before you start.

What is ashwagandha?

Ashwagandha (Withania somnifera) is a shrub native to India and parts of Africa. It has been used for centuries in Ayurvedic practice and is now one of the most widely sold herbal supplements in the United States. Manufacturers market it as an adaptogen, a traditional-use concept describing a substance said to help the body resist and adapt to physical, chemical, and biological stress. The NIH Office of Dietary Supplements notes that adaptogen is a traditional-use concept, not an established nutrient function recognized by regulatory bodies.

What is in it?

According to the NIH Office of Dietary Supplements, ashwagandha is rich in phytochemicals, chiefly steroidal lactones called withanolides, along with alkaloids. Researchers believe these compounds drive many of the proposed effects seen in laboratory and clinical studies. Different commercial extracts vary in their withanolide content, which makes comparing products and study results difficult.

No established daily target or upper limit

Unlike vitamins and minerals, ashwagandha has no Dietary Reference Intake, no adult target intake, and no established upper limit, according to the NIH Office of Dietary Supplements. Because there is no official benchmark, consumers should consult a clinician or pharmacist for personal dosing guidance rather than relying on label claims alone.

What the research shows: an honest evidence grade

The NIH Office of Dietary Supplements has reviewed the available human trial data and assigned the following evidence grades:

• Perceived stress and anxiety, and serum cortisol levels: Ashwagandha extracts may reduce perceived stress and anxiety and lower serum cortisol. Evidence grade: Limited.
• Sleep quality: Ashwagandha extracts may improve sleep quality, efficiency, total sleep time, and sleep latency, especially in people with insomnia. Evidence grade: Limited.
• Adaptogen claim (resisting stress): The claim that ashwagandha helps the body resist stress as a true adaptogen is supported by Insufficient evidence at this time.
• Cognitive function: Claims that ashwagandha improves cognitive function are also supported by only Insufficient evidence.

A limited grade means early findings are promising but the body of research is small, short in duration, or inconsistent enough that firm conclusions cannot yet be drawn. An insufficient grade means the current evidence does not allow any reliable conclusion. Neither grade supports treating or curing a condition. As required by law, supplements are not intended to diagnose, treat, cure or prevent any disease, and these statements have not been evaluated by the FDA.

Safety: what is known and what is not

The NIH Office of Dietary Supplements notes that ashwagandha appears well tolerated for up to about three months of use. Its long-term safety, meaning use beyond roughly three months, is not yet known.

Common side effects

Most reported side effects are mild and include:

• Loose stools
• Nausea
• Drowsiness
• Stomach upset

More serious concerns

A small number of more serious effects have been reported, according to the NIH Office of Dietary Supplements. These include adverse effects on liver function and effects on thyroid function. These reports are rare but are important to be aware of, particularly if you already have a liver or thyroid condition.

Pregnancy

Some experts advise against ashwagandha use during pregnancy. The NIH Office of Dietary Supplements notes that some reports raise concern, so pregnant women should speak with their doctor before using this supplement.

Drug and medication interactions

Because ashwagandha can affect several physiological systems, it has the potential to interact with certain medications. The NIH Office of Dietary Supplements identifies the following areas of concern. Always talk to a doctor or pharmacist before combining any supplement with prescription or over-the-counter medications.

• Thyroid hormone medications: Ashwagandha may affect thyroid function. Small increases in T4 have been reported, and studies in people with subclinical hypothyroidism have shown lowered TSH alongside increased T3 and T4. Cases of thyrotoxicosis have also been reported. This creates a meaningful potential interaction with thyroid medications.
• Antidiabetes medications: Ashwagandha may affect blood glucose levels, which could alter how antidiabetes drugs work and affect blood sugar control.
• Antihypertensive medications: Ashwagandha may affect blood pressure, potentially adding to or working against the effect of blood pressure medications.
• Immunosuppressants: Ashwagandha may stimulate immune activity, which could counteract medications used to suppress the immune system, such as those taken after an organ transplant or for autoimmune conditions.

Practical guidance before you buy

If you are considering ashwagandha, the following steps are worth taking before you start:

• Talk to your doctor or pharmacist, especially if you take any prescription medication, have a liver condition, a thyroid disorder, diabetes, or high blood pressure.
• Do not use ashwagandha as a replacement for any prescribed treatment for anxiety, stress, or any other condition.
• Keep use to the short term, roughly up to three months, given the current limits of long-term safety data.
• Choose products that have been third-party tested for purity and withanolide content, since supplement quality varies widely.
• Stop use and contact a healthcare provider if you notice unusual fatigue, yellowing of the skin or eyes, or any other unexpected symptom.

The bottom line

Ashwagandha is one of the better-studied herbal supplements, and early trial data on stress, anxiety, and sleep are cautiously encouraging. However, the NIH Office of Dietary Supplements rates that evidence as limited, not strong, and rates the broader adaptogen claim as insufficient. There is no established daily target or upper limit, and long-term safety data are lacking. For most healthy adults who are not pregnant and not taking interacting medications, short-term use appears to carry relatively low risk, but the decision is best made in conversation with a qualified healthcare provider who knows your full health picture.