Many people are convinced their extreme fatigue, brain fog, and trouble sleeping are caused by a condition that most medical practitioners say doesn't exist.

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It seems like everyone's talking about adrenal fatigue, and it's pretty easy to see why. The condition's extremely-common-yet hard-to-pin-down symptoms include fatigue, body aches, trouble sleeping, and dark under-eye circles, and adrenal fatigue wraps them up in a tidy diagnosis that can supposedly be treated with a cocktail of supplements.

Thing is, there's no scientific evidence this condition actually exists.

An alternative medicine specialist named James L. Wilson first introduced the concept of adrenal fatigue with his 1998 book, Adrenal Fatigue: The 21st Century Stress Syndrome. The condition, as he explained it, is a group of non-specific symptoms associated with "below optimal adrenal function resulting from stress." When the adrenals (small glands that sit on top of the kidneys and produce vital hormones and help the body to regulate metabolism and respond to stress) are overtaxed, he argued, we can suffer from everything from "'gray' feelings" to the inability to leave bed for more than a few hours. Wilson offered "unique dietary supplements" as the remedy.

Nearly two decades later, there's still no way to test for the condition. What's more, researchers have uncovered no concrete evidence that stress actually does drain the adrenal glands. The Endocrine Society, a group representing more than 18,000 physicians and scientists around the world, doesn't mince words in its fact sheet: "'Adrenal fatigue' is not a real medical condition. There are no scientific facts to support the theory that long-term mental, emotional, or physical stress drains the adrenal glands and causes many common symptoms."

"The symptoms people experience [when they believe they have adrenal fatigue] are very real, and sometimes it's difficult to have symptoms and not have a diagnosis, so that could be where the persistent myth of 'adrenal fatigue' syndrome comes from," says Salila Kurra, MD, co-director of the Columbia Adrenal Center and assistant professor of medicine at Columbia University Medical Center in New York City.

There really is harm in believing that myth and "waiting for the research to catch up," as some people put it, says Marilyn Tan, MD, an endocrinologist with Stanford Health Care and clinical assistant professor of medicine at Stanford School of Medicine in California. "Symptoms of fatigue, body aches, trouble sleeping, indigestion, and nervousness are non-specific and could be due to a variety of other diseases, including sleep disorders, depression, irritable bowel syndrome, and thyroid disease," she explains. "To attribute all symptoms to a single diagnosis of 'adrenal fatigue' risks missing the detection of other treatable underlying diseases."

Confusing matters, there is a similarly-named condition that's widely accepted in the medical community, with research supporting its existence: adrenal insufficiency.

Primary adrenal insufficiency, also known as Addison's disease, occurs when the adrenal glands are damaged and can no longer produce enough cortisol, a hormone that plays a role in bone growth, blood pressure control, immune system function, metabolism, nervous system function, and stress response. It's very rare, affecting 110 to 144 of every 1 million people in developed countries. Autoimmune disorders cause about 80% of cases. Secondary adrenal insufficiency, on the other hand, is much more common, and occurs when the pituitary gland won't produce enough of a hormone that stimulates the adrenal gland to produce cortisol. It can be brought on by long-term glucocorticoid (steroid) use, pituitary disease, radiation, or other causes.

Both types of adrenal insufficiency can be detected with lab tests, and patients suspected of having it might receive, for example, a morning blood test to measure their production of cortisol. "The reason you check cortisol levels in the morning to look for whether or not someone is making enough is because that's when it should be the highest," Dr. Kurra explains. "Most people with a normal sleep/wake cycle should have a spike of cortisol around 8 a.m." Adrenal insufficiency is a serious condition treated with hormone substitution and replacement, and people diagnosed with it are urged to carry medical identification so that they can receive appropriate help in the event of a crisis.

If your adrenal glands aren't working properly, your primary-care physician will likely refer you to a specialist. And take note: Although proponents of "adrenal fatigue" suggest treating yourself with over-the-counter supplements that promise "adrenal support" or "thyroid support," you absolutely should not do this to treat potential adrenal concerns of any kind. "If you take a supplement that has thyroid extract or adrenal extract, it could cause the symptoms of having too much of those hormones," Dr. Kurra says. "Supplements can also make your own glands—especially the adrenal glands, if you're taking some derivative of cortisol—stop working. Then, if you stop taking the supplement all of a sudden, your adrenal glands may not work; it takes time for them to 'wake up' again."

Plus, supplements have other drawbacks. "Most supplements are not only costly and not covered by insurance, but they are not FDA regulated," says Dr. Tan. "We do not have a full understanding of all of the effects of various supplements. Even though components of the supplements may be 'natural,' that does not mean they will not affect the body in adverse ways." They can also make it trickier for your doctor to help you: "Supplements make testing [for hormone levels] really difficult," Dr. Kurra adds. "We don't really know the active ingredients; there can actually be something in a supplement that gives false positive or false negative results." This is especially true when it comes to herbal remedies and multi-ingredient supplements; mega-doses of vitamins can have their own drawbacks, of course, but they are less likely to cause harm.

If you're experiencing symptoms that may have led you to believe you have adrenal fatigue, it's time to reach out to your primary care doctor, says Dr. Kurra. "A primary-care physician can help guide you in the direction of your treatment and, if you need to, help you find a subspecialist." Dr. Tan concurs: "This provider is the one who will be coordinating all your care between various other providers. Since the symptoms attributed to 'adrenal fatigue' can be non-specific, it is best to speak with your primary care provider so that he or she can better assess whether there is another obvious underlying cause." You've got all the background you need; now, make that call.