22 Trials: Ashwagandha May Improve Anxiety, Stress, & Sleep

RADiKAL EVIDENCE

Our analysis addresses the following question:

“Does ashwagandha improve anxiety, stress, or sleep better than placebo?”

To answer this question:

We analyzed 990 data points from 22 relevant clinical trials (1,504 participants) conducted over the past 23 years.

Here’s the most objective answer:

Ashwagandha might improve anxiety, stress, and sleep better than placebo in the general population.

But people with specific medical conditions may not benefit as much.

Let’s explore.

Last Literature Review: Nov. 2023. Last Content Update: Nov. 22, 2023. Content Policy & Disclaimer.

Author Bio Icon
This image shows a summary table comparing ashwagandha vs. placebo and ashwagandha’s effect on anxiety, stress, and sleep. It shows that ashwagandha likely reduces anxiety, lowers stress, and improves sleep in the general adult population and in generally healthy people. Ashwagandha likely reduces anxiety but doesn’t improve sleep in people with generalized anxiety disorder. Ashwagandha might reduce anxiety and improve sleep in people with insomnia. Ashwagandha may reduce anxiety and lower stress better than placebo in people with schizophrenia. Finally, ashwagandha may not effectively reduce anxiety in bipolar disorder nor lower stress in type 2 diabetes mellitus.

Key Stats

  • Compared to trials conducted in the U.S. and Australia, trials from India and Iran were 2.1 times more likely to find that ashwagandha was more effective than placebo. (Stat Image)
  • In up to 71.4% of clinical trials, the study’s subjects may have been able to determine if they got a treatment or “placebo” due to ashwagandha’s unique smell. (Stat Image)
  • 69.2% of trials found that ashwagandha might reduce anxiety better than placebo. (Stat Image)
  • 72.7% of trials found that ashwagandha might lower stress better than placebo. (Stat Image)
  • 70.0% of trials found that ashwagandha might improve sleep quality better than placebo. (Stat Image)
  • 38.1% of clinical trials had financial conflicts of interest. (Stat Image)
  • 28.6% of clinical trial abstracts incorrectly implied that ashwagandha improves anxiety, stress, or sleep. In fact, the data inside the full paper made it clear that ashwagandha didn’t work better than placebo. (Stat Image)

1 Minute Summary

Ashwagandha is also called Winter Cherry or Indian Ginseng. (R)

It contains active compounds called withanolides, withanosides, and withaferins. (R)

It’s believed such compounds might reduce anxiety, lower stress, and improve sleep. They may do so by affecting specific receptors in the brain, like GABA receptors. (R, R)

Prescription medications, like benzodiazepines used for anxiety, affect GABA receptors as well. (R, R)

As many people know: anxiety, stress, and sleep quality are often closely related. (R)

A person’s anxiety, stress, or sleep quality can be measured objectively or subjectively.

Objectively:

Cortisol is the “stress hormone”. We can objectively measure the levels of cortisol or changes in blood pressure in order to approximate a person’s level of stress. But lab-based measurements like these don’t always reflect how a person actually feels. (R, R)

For example, a person with high blood pressure isn’t necessarily stressed. So too, cortisol levels can change for a wide range of reasons other than psychological stress.

Subjectively:

Questionnaires transform a person’s subjective feelings and experiences into a somewhat objective “score”. Questionnaires are imperfect as well. But it’s something we can work with.

Therefore:

Our analysis reflects the way ashwagandha might affect anxiety, stress, or sleep. Mainly through the data provided by relevant (scientific) questionnaires. These scientific questionnaires were answered by researchers and patients in clinical trials.

We found 22 clinical trials that provide such data.

Here’s what these trials reveal:

It appears that ashwagandha may reduce anxiety and stress better than placebo.

It also appears that ashwagandha may improve the quality of sleep better than placebo.

However:

These results are not consistent across various medical conditions. The Results section of this analysis goes into further detail about this.

Furthermore:

The Discussion section of this analysis goes over some concerns we have about the data provided by the clinical trials we found. The data may not be as reliable as it seems.

In summary:

While ashwagandha’s effectiveness appears quite promising, higher-reliability trials are lacking.

Results

Anxiety

This image shows that 69.2% (9 of 13) clinical trials found that ashwagandha might reduce anxiety significantly better than placebo in adults in the general population.

13 clinical trials provide data on anxiety. These trials included a total of 801 participants.

The trials were randomized, double-masked, and placebo-controlled. They compared an ashwagandha supplement to placebo.

Collectively, these trials focused on individuals who met one of the following criteria:

  • Generally healthy
  • Diagnosed with insomnia
  • Diagnosed with schizophrenia
  • Diagnosed with bipolar disorder
  • Diagnosed with generalized anxiety disorder (GAD)

Here are the results:

69.2% (9 of 13) clinical trials found that ashwagandha might reduce anxiety significantly better than placebo in adults in the general population. [Moderate Evidence]

Stress

This image shows that 72.7% (8 of 11) clinical trials found that ashwagandha might lower stress significantly better than placebo in adults in the general population.

11 clinical trials provide data on psychological stress. These trials included a total of 838 participants.

The trials were randomized, double-masked, and placebo-controlled. They compared an ashwagandha supplement to placebo.

Collectively, these trials focused on individuals who met one of the following criteria:

  • Generally healthy
  • Overweight or with obesity
  • Diagnosed with schizophrenia

Here are the results:

72.7% (8 of 11) clinical trials found that ashwagandha might lower stress significantly better than placebo in adults in the general population. [Moderate Evidence]

Sleep

This image shows that 70.0% (7 of 10) clinical trials found that ashwagandha might improve sleep quality significantly better than placebo in adults in the general population.

10 clinical trials provide data on sleep quality. These trials included a total of 722 participants.

The trials were randomized, double-masked, and placebo-controlled. They compared an ashwagandha supplement to placebo.

Collectively, these trials focused on individuals who met one of the following criteria:

  • Generally healthy
  • Diagnosed with insomnia
  • Diagnosed with generalized anxiety disorder (GAD)

Here are the results:

70.0% (7 of 10) clinical trials found that ashwagandha might improve sleep quality significantly better than placebo in adults in the general population. [Moderate Evidence]

Bipolar Disorder

This image shows that 100% (1 of 1) clinical trials found that ashwagandha is unlikely to reduce anxiety significantly better than placebo in adults with bipolar disorder.

1 clinical trial focused on individuals with bipolar disorder.

This trial was randomized, double-masked, and placebo-controlled.

Here are the results:

100% (1 of 1) clinical trials found that ashwagandha is unlikely to reduce anxiety significantly better than placebo in adults with bipolar disorder. [Weaker Evidence]

Diabetes (Type 2)

This image shows that 100% (1 of 1) clinical trials found that ashwagandha is unlikely to lower stress significantly better than placebo in adults with type 2 diabetes.

1 clinical trial focused on individuals with type 2 diabetes.

This trial was randomized but not double-masked.

Here are the results:

100% (1 of 1) clinical trials found that ashwagandha is unlikely to lower stress significantly better than placebo in adults with type 2 diabetes. [Weaker Evidence]

Generalized Anxiety Disorder

3 clinical trials focused on individuals diagnosed with generalized anxiety disorder (GAD). These trials included a total of 165 participants.

The trials were randomized, double-masked, and placebo-controlled.

3 trials provided data on anxiety and 1 of these trials also provided data on sleep quality.

Here are the results:

This image shows that 66.7% (2 of 3) clinical trials found that ashwagandha might reduce anxiety significantly better than placebo in adults with generalized anxiety disorder.

66.7% (2 of 3) clinical trials found that ashwagandha might reduce anxiety significantly better than placebo in adults with generalized anxiety disorder. [Moderate Evidence]

This image shows that 100% (1 of 1) clinical trials found that ashwagandha is unlikely to improve sleep quality significantly better than placebo in adults with generalized anxiety disorder.

100% (1 of 1) clinical trials found that ashwagandha is unlikely to improve sleep quality significantly better than placebo in adults with generalized anxiety disorder. [Weaker Evidence]

Healthy (Generally)

12 clinical trials focused on generally healthy individuals. These trials included a total of 860 participants.

The trials were randomized, double-masked, and placebo-controlled.

Some trials provided data exclusively on anxiety, stress, or sleep quality. Other trials provided data on any two or all three of these outcomes.

Here are the results:

This image shows that 66.7% (4 of 6) clinical trials found that ashwagandha might reduce anxiety significantly better than placebo in generally healthy adults.

66.7% (4 of 6) clinical trials found that ashwagandha might reduce anxiety significantly better than placebo in generally healthy adults. [Moderate Evidence]

This image shows that 75.0% (6 of 8) clinical trials found that ashwagandha might lower stress significantly better than placebo in generally healthy adults.

75.0% (6 of 8) clinical trials found that ashwagandha might lower stress significantly better than placebo in generally healthy adults. [Moderate Evidence]

This image shows that 85.7% (6 of 7) clinical trials found that ashwagandha might improve sleep quality significantly better than placebo in generally healthy adults.

85.7% (6 of 7) clinical trials found that ashwagandha might improve sleep quality significantly better than placebo in generally healthy adults. [Moderate Evidence]

Insomnia

2 clinical trials focused on individuals with insomnia. These trials included a total of 138 participants.

The trials were randomized, double-masked, and placebo-controlled.

Here are the results:

This image shows that 100% (2 of 2) clinical trials found that ashwagandha might reduce anxiety significantly better than placebo in adults with insomnia.

100% (2 of 2) clinical trials found that ashwagandha might reduce anxiety significantly better than placebo in adults with insomnia. [Weaker Evidence]

This image shows that 50.0% (1 of 2) clinical trials found that ashwagandha might improve sleep quality significantly better than placebo in adults with insomnia.

50.0% (1 of 2) clinical trials found that ashwagandha might improve sleep quality significantly better than placebo in adults with insomnia. [Weaker Evidence]

Overweight & Obesity

This image shows that 50.0% (1 of 2) clinical trials found that ashwagandha might lower stress significantly better than placebo in overweight or obese adults.

2 clinical trials focused on overweight or obese adults. These trials included a total of 170 participants.

The trials were randomized, double-masked, and placebo-controlled.

Here are the results:

50.0% (1 of 2) clinical trials found that ashwagandha might lower stress significantly better than placebo in overweight or obese adults. [Weaker Evidence]

Schizophrenia

1 clinical trial focused on adults diagnosed with schizophrenia.

The trial was randomized, double-masked, and placebo-controlled.

It provided information on anxiety and stress.

Here are the results:

This image shows that 100% (1 of 1) clinical trials found that ashwagandha might reduce anxiety significantly better than placebo in adults with schizophrenia.

100% (1 of 1) clinical trials found that ashwagandha might reduce anxiety significantly better than placebo in adults with schizophrenia. [Weaker Evidence]

This image shows that 100% (1 of 1) clinical trials found that ashwagandha might lower stress significantly better than placebo in adults with schizophrenia.

100% (1 of 1) clinical trials found that ashwagandha might lower stress significantly better than placebo in adults with schizophrenia. [Weaker Evidence]

Dosage

The following ashwagandha dosage information is not medical advice and is a summation of clinical trial data only.

The traditional dosage of ashwagandha root powder is 3 g twice a day, for a wide range of conditions. (R)

Clinical trial data suggests that it’s generally ok to take ashwagandha every day, when healthy.

But the ashwagandha dosage may need to be carefully adjusted. That’s because researchers caution that high amounts of specific withanolides in the ashwagandha root can be toxic.

Anxiety

This image shows that The ashwagandha dose used for anxiety in clinical trials was 125 mg – 4 g, taken 1–3 times a day, for 1–3 months.

The ashwagandha dose used for anxiety in clinical trials was 125 mg – 4 g, taken 1–3 times a day, for 1–3 months.

Where data allows:

The withanolide content was approximately 2.5%–35% (including withanosides and sitoindosides), depending on formulation.

The withaferin A content was approximately 1%–2%.

Stress

This image shows that The ashwagandha dose for used for stress in clinical trials was 125 mg – 500 mg, taken 1–2 times a day, for 1–3 months.

The ashwagandha dose for used for stress in clinical trials was 125 mg – 500 mg, taken 1–2 times a day, for 1–3 months.

Where data allows:

The withanolide content was approximately 1.5%–11.9%, depending on formulation.

The withaferin A content was approximately 1.05%, depending on formulation.

Sleep

This image shows that The ashwagandha dose used for sleep in clinical trials was 125 mg – 4 g of an ashwagandha supplement, 1–3 times a day, for 1–3 months.

The ashwagandha dose used for sleep in clinical trials was 125 mg – 4 g of an ashwagandha supplement, 1–3 times a day, for 1–3 months.

Where data allows:

The withanolide content was approximately 0.7%–11.09%, depending on formulation.

The withaferin A content was approximately 1%–2%, depending on formulation.

Side Effects

The following is not medical advice and is a summation of clinical trial data only.

Most researchers noted that people who took ashwagandha didn’t experience any adverse events (negative side effects). Or, the researchers noted that the side effect profile for ashwagandha was statistically similar to placebo.

Nonetheless, Ashwagandha appears to have at least the potential for side effects that deserve monitoring.

For example, 3.3%-21% of trial participants said ashwagandha made them sleepy. While this may help people sleep, it may be counterproductive or outright dangerous for some professions and circumstances.

Digestive disturbances were quite common as well.

Commonly Reported

In clinical trials, the most commonly reported side effects in people who took ashwagandha included:

  • Heavy-headedness (4%–23.5%)
  • Sleepiness (3.3%–21%)
  • Nausea (3.3%–20%)
  • Diarrhea (8%–18.1%)
  • Gastritis (17.6%)
  • Lethargy/tiredness/fatigue (2%–11.8%)
  • Decreased sleep (11.8%)
  • Digestive disturbance (10%)
  • Abdominal discomfort (9.1%)
  • Heartburn (9.1%)
  • Mood disturbance/changes (7%)
  • Nightmares (6.7%)
  • Acid reflux/hyperacidity (4%–6.3%)
  • Allergic dermatitis/rash (3.3%–6.3%)
  • Headache (2%–6.1%)
  • Dry mouth (6.1%)
  • Hyperactivity (6.1%)
  • Weight gain (6.1%)
  • Worsening of psychiatric condition (6.1%)
  • Decreased appetite (3.3%–5.9%)
  • Increased appetite (2%–5.9%)
  • Migraines (2%–5.9%)
  • Numbness in the hands (5.9%)
  • Blurred vision (4%)
  • Ear pain (4%)
  • Giddiness (4%)
  • Viral infection (3.1%–3.3%)
  • Constipation (3.3%)
  • Dizziness (3.3%)
  • Flatulence (3.3%)
  • Frequent urination (3.3%)
  • Nasal congestion (3.3%)
  • Swollen feet (3.3%)
  • Worsening of depression (3.3%)

For clarity, the list above is presented as:

  • Reported side effect (approximate percentage of people who took ashwagandha that experienced the side effect in any given trial, where data allows.)

Important Note

Many clinical trials purposefully excluded people with a known history of side effects and allergy to ashwagandha.

Therefore, the side effect profile herein may be an underestimation of the possible variety and risk of side effects that ashwagandha may truly present.

Discussion

Geographic Bias

This image shows that compared to trials conducted in the U.S. and Australia: Trials conducted in India and Iran were 2.1 times more likely to report that ashwagandha improved anxiety, stress, or sleep.

15 clinical trials were conducted in India, 5 in the U.S., 1 in Iran, and 1 in Australia.

Evidence shows that falsified data or fake clinical trials are a problem in medical literature. Especially from specific countries.

For example, 62% of closely-inspected Indian trials submitted to Anaesthesia had false data. 46% of closely-inspected Indian trials were found to be fatally flawed. The potential reasons for this are numerous. (R)

Similarly, our review on the effect of beet juice on blood pressure discovered a geographic bias as well.

Compared to trials conducted in the rest of the world:

Trials conducted in the U.S. or U.K. were 1.85 times more likely to find that beets lowered blood pressure significantly better than placebo/control.

In this particular case, financial conflicts of interest may explain our finding.

(U.S. and U.K. trials were more likely to have connections to commercial interests.)

What about the trials on ashwagandha’s effects on anxiety, stress, or sleep?

In the 6 clinical trials conducted in the U.S. and Australia:

37.5% of results showed ashwagandha worked better than placebo for anxiety, stress, or sleep.

In the 16 clinical trials conducted in India and Iran:

77.8% of results showed ashwagandha worked better than placebo for anxiety, stress, or sleep.

In other words, as compared to trials conducted in the U.S. and Australia:

Trials conducted in India and Iran were 2.1 times more likely to report that ashwagandha improved anxiety, stress, or sleep.

There could be multiple explanations for this. Our analysis isn’t an implication that there’s outright data manipulation of any sort as we didn’t examine for this.

Genetic, environmental, and cultural differences between populations can also influence clinical trial results. (R)

One thing is very clear from this analysis:

Further high quality trials outside of India are necessary to clarify ashwagandha’s effect on anxiety, stress, and sleep in different populations.

Financial Bias

This image shows that 38.1% (8 of 21) clinical trials reported significant financial conflicts of interest.

Financial conflicts of interest often correlate to favorable clinical trial results. (R)

Where data allowed, we found that 38.1% (8 of 21) clinical trials reported significant financial conflicts of interest.

Often, this meant funding from an ashwagandha-related supplement company. Or, it meant one of the researchers had a stake in an ashwagandha-related company.

Of the trials with no stated financial conflicts of interest:

68.2% of results showed ashwagandha worked better than placebo for anxiety, stress, or sleep.

Of the trials with stated financial conflicts of interest:

69.2% of results showed ashwagandha worked better than placebo for anxiety, stress, or sleep.

In other words:

Trials with financial conflicts of interest were slightly more likely to report favorable results vs. trials with no stated conflicts of interest.

This is likely a conservative estimate.

That’s because undisclosed conflicts of interest are a common problem in medical literature. (R)

That means many of the trials that stated “no conflicts of interest” may not have done so honestly.

We discovered as much in our review on the effect of beet juice on blood pressure.

Highest Reliability Results

We filtered the clinical trials that we found to match the following criteria:

  • Randomized, double-blind, placebo-controlled trials
  • Trials where the placebo was indistinguishable from ashwagandha (details: Smell of Horse)
  • Trials with no reported financial conflicts of interest

We accounted for abstract bias (details: Abstract Bias).

Only 5 clinical trials met all such criteria (“higher reliability trials”).

The other 17 trials did not meet one or more of these criteria (“lower reliability trials”).

Of the higher reliability trials:

66.7% of results showed ashwagandha worked better than placebo for anxiety, stress, or sleep.

Of the lower reliability trials:

69.0% of results showed ashwagandha worked better than placebo for anxiety, stress, or sleep.

Lower reliability trials were slightly more likely to report favorable results for ashwagandha.

Abstract Bias

This image shows that 28.6% (6 of 21) clinical trials in this review had a misleading abstract.

The results and conclusions in study abstracts can be misleading. (R)

For example, a study may claim that ashwagandha lowers stress.

But the data in the trial itself fails to support such an assertion.

A reader who skims the abstract alone may walk away thinking that ashwagandha helps beat stress.

Where data allowed, we found that 28.6% (6 of 21) clinical trials in this review had a misleading abstract.

Most often, the misdirection had to do with the following:

The abstract claimed that ashwagandha helped improve anxiety, stress, or sleep.

The data actually showed that ashwagandha didn’t improve anxiety, stress, or sleep better than placebo.

Where did the misdirection occur?

1. People who took ashwagandha experienced an improvement in anxiety, stress, or sleep.

2. But so did the people who took a placebo.

3. The effect of ashwagandha wasn’t significantly different from placebo.

The abstract stated #1 without mentioning #3.

Smell of Horse

71.4% of clnical trials may not have properly controlled for Ashwagandha's unique horse-like smell.

Ashwagandha translates as “smell of horse”. Where “ashwa” means horse, and “gandha” means smell. As this suggests, ashwagandha roots have a distinct horse-like smell. (R, R, R)

Researchers investigating ashwagandha’s effects on anxiety, stress, and sleep recognize this fact. (R)

To be properly masked, a placebo needs to be as indistinguishable from ashwagandha as possible.

Of the 21 trials we had enough data on for this subanalysis:

Only 28.6% (6 of 21) trials explicitly mentioned they controlled for ashwagandha’s distinct smell.

(These 6 trials also ensured that the ashwagandha treatment matched the placebo for color, size, shape, etc.)

In other words:

In up to 71.4% of clinical trials, the study’s subjects may have been able to determine if they got a treatment or “placebo” due to ashwagandha’s unique smell. This might have altered the results in unknown ways.

What happened to the placebos in the other 15 trials?

We don’t know.

Perhaps the researchers controlled for the smell but didn’t mention it in the paper. Perhaps they didn’t control for the smell. In that case, the participants may have known if they got ashwagandha or placebo. This would, of course, influence the results.

This is nothing new.

Inadequately masked placebos are a recognized problem in clinical literature. (R)

Of the 6 (“smell-controlled”) trials:

75.0% of results showed ashwagandha worked better than placebo for anxiety, stress, or sleep.

Of the 15 (possibly “non-smell-controlled”) trials:

66.7% of results showed ashwagandha worked better than placebo for anxiety, stress, or sleep.

Trials that explicitly mentioned they controlled for ashwagandha’s smell were more likely to report that it was superior to placebo.

Double-Blind Bias

The term “double-blind” (“double-masked”) doesn’t have a standardized definition.

Many people assume “double-blind” implies that the study’s subjects didn’t know if they got treatment or placebo. This isn’t always the case.

There are up to 11 types of individuals that could be blinded in a clinical trial.

This includes doctors, patients, statisticians, technicians, outcomes assessors, etc. (R)

Therefore, the term “double-blind” is often ambiguous, not defined, or even misused.

We were able to closely examine 21 clinical trials for this section’s analysis.

Of these 21 trials:

20 (95.2%) claimed to be “double-blind”. For many, this automatically implies the study’s subjects were “blind”.

(The subjects supposedly didn’t know if they got ashwagandha or placebo).

Of these 20 “double-blind” trials:

25.0% (5 of 20) did not state that the study subjects were “blinded”. This could simply have been an omission and the subjects were actually blinded. Or it might mean the study’s subjects knew that they got ashwagandha or placebo, while other trial participants (e.g. statisticians) were blinded instead.

15 double-blind trials confirmed that the study’s subjects were, indeed, “blind”.

Of the 15 double-blind trials where the subjects were confirmed to be “blind”:

73.1% of results showed ashwagandha worked better than placebo for anxiety, stress, or sleep.

Of the 5 double-blind trials where the subjects may not have been “blind”:

62.5% of results showed ashwagandha worked better than placebo for anxiety, stress, or sleep.

Double-blind trials that confirmed the subjects were blind were more likely to report that ashwagandha is superior to placebo.

Methods

Clinical Question

Our literature review and analysis sought to answer the following clinical question:

“How does the consumption of isolated ashwagandha affect patient-centered measures of anxiety, stress, or sleep?”

Primary intervention of interest: Withania somnifera (L.) Dunal (Solanaceae) isolated from other likely active ingredients.

Primary outcomes of interest: questionnaire-based measures of anxiety or psychological distress, questionnaire-based and actigraphic measures of sleep quality or quantity.

Inclusion/Exclusion Criteria

The purpose of this literature review was to determine the direction of the effect that ashwagandha supplements have on a person’s anxiety, stress, or sleep.

We included studies that focused exclusively on the extracts and powders of the Withania somnifera plant, namely the roots and/or leaves.

We excluded any studies where the ashwagandha intervention was mixed with another product or supplement, such as another herb— unless the non-primary intervention comparator arm(s) excluded the ashwagandha product in an otherwise generally equivalent fashion, thereby allowing us to isolate the effect of ashwaganda in such cases.

We included studies where the primary or secondary endpoint data was derived from a questionnaire-based measure of anxiety or any form of psychological stress. Examples include, but are not limited to, the Hamilton Anxiety Rating Scale (HAM-A) and the Perceived Stress Scale (PQSI), respectively.

We included studies where the primary or secondary endpoint data was derived from a questionnaire-based measure of sleep quality or quantity, such as the Pittsburg Sleep Quality Index (PQSI) or an actigraphic measure of sleep quality or quantity.

We excluded endpoint data on measures of anxiety, stress, or sleep that were part of a composite (overall) score that did not allow us to isolate an individual score for each of anxiety, stress, or sleep.

We excluded endpoint data on non-patient-centered approximations of anxiety, stress, or sleep, such as—but not limited to—biomarker levels (e.g. cortisol), variations in heart rate, changes in blood pressure, and similar surrogate outcomes.

In order to gather the best available evidence for any potential cause-and-effect relationship pertinent to the clinical question, we focused on data solely from published, peer-reviewed, clinical trials and any meta-analyses thereof. This means we excluded observational and basic science literature and any meta-analyses thereof, any interim analyses, conference abstracts, whitepapers, and other non-peer-reviewed data.

We excluded all studies published in a non-English language.

We excluded all studies focused on individuals under the age of 18 years.

Search Strategy

Our clinical question, and primary interventions/outcomes of interest, largely defined our search strategy.

An initial literature search was conducted in November of 2023, using three distinct searches to maximize the number of relevant clinical trials we could find.

(See the Last Literature Review date in the beginning of this article to see when we last searched for any new trial data on this topic.)

Search #1:

Using PubMed, search #1 used search terms focused on identifying published studies where the primary intervention was any ashwagandha-based product (higher specificity, lower sensitivity intervention search) using a combination of keywords and wildcards. We didn’t use any keywords relevant to the primary outcomes of interest in order to maximize the sensitivity of this part of the search (lower specificity, higher sensitivity outcomes search).

The search terms were applied to the titles and abstracts of PubMed’s database.

Filters for clinical trials on humans, practice guidelines, and errata/retractions were applied.

Search #1 yielded 82 results.

Search #2:

Using PubMed, search #2 focused on maximizing the specificity of the outcomes search. Clinical trials related to anxiety, stress, and sleep were specifically searched for using a combination of keywords and wildcards while focusing on the primary intervention (ashwagandha) of interest at the same time.

Search #2 yielded 167 results.

Search #3:

Search #3 was a “sweep”.

The sweep is an acknowledgement that PubMed doesn’t contain all studies of interest (or may not at the time of our search) and that PubMed filters are imperfect and, on occasion, miscategorize or fail to categorize studies of interest. Moreover, search #1 and #2 are neither perfect nor exhaustive searches on their own.

Therefore:

Using search #1 and #2, we identified 9 systematic reviews and meta-analyses (SRMAs) of relevance to our clinical question.

We examined all of the studies included in these SRMAs of interest and identified a small number of clinical trials of interest missed by search #1 and #2.

Limitations

Our literature review did not include studies published in a language other than English.

Our search and analysis focused on patient-centered (questionnaire and actigraphic-based) measures of anxiety, psychological distress, and sleep.

We excluded surrogate measures that may be of relevance in some cases, such as changes in cortisol and blood pressure. Inclusion of such surrogate markers may have changed the results of this analysis. However, while the use of surrogate endpoints for anxiety, stress, and sleep may be useful in select cases, such relationships are not always well-correlated and may have little to do with the subjective (lived) patient experience. (R)

Our search may have missed trials where “ashwagandha” (or related terms) weren’t mentioned in the title/abstract but were actually used in the trial. We believe that our third search (the “sweep”) largely addressed such sensitivity/specificity concerns. However, we cannot exclude the possibility that the sweep also missed trials of interest, especially those with primary interventions or primary outcomes of interest not mentioned in the title nor abstract.

Virtually all of the trials that found that ashwagandha had a beneficial effect on anxiety, stress, or sleep mentioned this fact in the title/abstract. This means we likely found nearly all of the trials with a beneficial effect. Trials that didn’t find a beneficial effect were less likely to report this lack of effect in the title/abstract. Therefore, we believe that if we missed any relevant trials, it was likely trials that did not find a difference between ashwagandha and placebo. This means that ashwagandha may be less effective than our analysis suggests. In other words, we believe that our analysis might be systematically biased in favor of ashwagandha as a result of our review’s limitations.

We didn’t mathematically model the potential for publication bias. This may have further skewed our results in favor of ashwagandha.

Disclosure

We declare no conflicts of interest. We do not sell any supplements and this review hasn’t been sponsored by, nor is it affiliated with, any outside entity in any way.

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