If you believe TikTok and pastel-colored ad campaigns, here is an incomplete list of what ashwagandha can do: reduce stress, “kill” emotions, focus a frantic mind, squelch social anxiety, fend off depression, give you a boost at the gym.

The ashwagandha plant — a staple of Ayurvedic medicine for thousands of years — has gone mainstream in 2023. Yet experts say it’s still not clear if, and how, it works.

“It’s the same story with ashwagandha as it is for many, many dietary supplements, botanicals, herbals,” said D. Craig Hopp, a deputy division director at the National Center for Complementary and Integrative Health. The science on the supplement is murky, but people keep turning to it.

Here’s what is known about ashwagandha, and what to consider if you’re thinking of trying it.

What is ashwagandha and what is it believed to do?

Ashwagandha, a flowering shrub, belongs to a trendy class of supplements known as adaptogens — as in, they help your body adapt to stress. From its long history up to present day, ashwagandha has been used to treat insomnia and bolster the immune system, as well as to reduce stress. It’s also thought to boost testosterone, slow the physical effects of aging and more.

One of the reasons it’s so tricky to pin down what the supplement can do is that the ashwagandha plant is complex. There are hundreds of active compounds, and those you find in the root of the plant can vary widely from those found in the leaves, for example, said Dr. Pieter Cohen, an associate professor at Harvard Medical School who studies supplements.

“Talking about ashwagandha as one compound, as if it’s Tylenol or vitamin C, makes absolutely no sense,” he said.

What’s more, today’s supplements may contain higher concentrations of ingredients than are found in nature, said Lilian Cheung, a lecturer on nutrition at the Harvard T.H. Chan School of Public Health. That means an ashwagandha pill you buy at a health store, for example, is most likely not the same strength or type of ashwagandha that was traditionally used in Eastern medicine.

And because supplements are so loosely regulated in the U.S., it’s hard to know whether you’re even purchasing actual ashwagandha.

Does ashwagandha work?

As with much of herbal medicine, there are very few rigorous, double-blind studies evaluating ashwagandha. Much of the knowledge around its benefits stems from its traditional usage, said Dr. Yufang Lin, an integrative medicine specialist at the Cleveland Clinic.

The studies on ashwagandha that do exist tend to have relatively small numbers of human participants. One meta-analysis consolidated 12 of these smaller studies and showed a promising link between the plant and stress relief — but additional research would be needed to demonstrate that connection on a larger scale, said Dr. Anand Dhruva, a professor of medicine and director of education at the Osher Center for Integrative Health at the University of California, San Francisco.

Dr. Hopp said that “oftentimes, people think, ‘Well, it’s been used for thousands of years — it must be good for something, otherwise people wouldn’t keep using it.’” But without definitive research demonstrating what ashwagandha can do, consumers are left without clear answers.

There are a few theories, though, about why people may report less stress after taking ashwagandha, based on what experts know about adaptogens overall. Dr. Melinda Ring, an integrative medicine specialist at Northwestern Medicine, said that the plant could potentially suppress dopamine receptors in the brain, which go into overdrive when we’re stressed. Ashwagandha is also thought to help regulate cortisol levels, she added. There’s also the power of the placebo effect — people can persuade themselves that their anxiety is abating.

As for the numb feeling that TikTok users claim to get, it’s possible that some people experience an easing of their stress and anxiety as blunting emotions overall, Dr. Ring said. “But in my experience, and in the 1,000 years that it’s been used, that is generally not the effect,” she said.

For ashwagandha to have a calming influence, in theory, Dr. Lin said, a person would need to consume it regularly (around twice a day) for several weeks — a capsule or drink infused with the supplement isn’t likely to have the kind of instant effect some manufacturers advertise. She recommended taking it during brief, discrete periods, not every day in perpetuity.

A short meditation, or even a cup of tea, is more likely to ground you during a moment of intense stress, she added.

“Adaptogens don’t work like an aspirin,” Dr. Ring echoed. “They work over time.”

Is ashwagandha safe?

For most people, ashwagandha has relatively minimal side effects, experts said. Some who consume it may experience an upset stomach, nausea or diarrhea; in rare cases, those using it may vomit.

Ashwagandha could be dangerous for certain groups, however. People with thyroid conditions should take caution with the supplement, and those with autoimmune disorders or hormone-sensitive prostate cancer should avoid it, Dr. Ring said. People who are pregnant should also steer clear, she said, because it may damage or terminate a pregnancy.

Experts interviewed for this story recommended talking with your doctor before trying ashwagandha, and being sure to ask if it could interact with any medications you’re taking. It’s also important to choose a supplement that comes from a vetted source. Dr. Cohen recommended seeking out supplements that have been certified by a third-party organization, such as the U.S. Pharmacopeia or NSF, but even that extra step of validation can’t confirm the active compounds that are actually inside an ashwagandha product.

“Right now, American consumers remain completely in the dark,” Dr. Cohen said.