(NEXSTAR) — Nearly one in five adults in the U.S. who had COVID-19 is still dealing with symptoms of the virus, a phenomenon commonly known as “long COVID.” A new study found there may be more than one variation of long COVID.

The study, out of King’s College in London, was published on MedRxiv last week but hasn’t yet been peer-reviewed. The findings suggest that there are three different types of long COVID, each with their own symptoms.

Researchers reviewed the cases of 1,459 people living in the U.K. who were experiencing symptoms for 12 weeks after testing positive for COVID. These patients could be divided into three “symptom profiles.”

The first was comprised of long COVID patients experiencing neurological symptoms. That includes changes to or loss of their sense of smell; fatigue; brain fog; depression; delirium; and headache. According to the study, most patients fitting this group likely had COVID early on, or the alpha or delta variants.

The second group reported cardiorespiratory symptoms, such as difficulty breathing and chest pains, and potential lung damage. Researchers say patients that had wild-type COVID — the original virus before variants — largely comprised this group.

The third, which was found among all COVID variants, included abdominal symptoms and muscle aches.

None of these symptoms are new – the Centers for Disease Control and Prevention (CDC) list 19 commonly-reported symptoms broken down into five categories: general, respiratory and heart, neurological, digestive, and other.

While the study acknowledged additional research is needed surrounding long COVID, researchers said their findings could help patients and healthcare providers better understand the individual’s condition and life with post-COVID.

Much remains unknown about the condition, including just how prevalent it is.

The federal government recently released information on what services are available to those who are experiencing long COVID, and what sort of research is still needed to understand the condition. This comes after President Joe Biden issued a memorandum in April outlining what is needed to support individuals facing long COVID.

The CDC says they are continuing to work with researchers to learn about the condition.