TUESDAY, Nov. 3, 2026 (HealthDay News) — Troubling side effects — including sleep paralysis and nightmares — are causing some people to stop taking a cutting-edge insomnia drug, a new study says.

The drug lemborexant (Dayvigo) helped people fall asleep faster and stay asleep longer than a placebo in clinical trials that contributed to its U.S. approval in 2019, researchers said.

But about 1 in 4 online reviewers of the drug have either stopped or plan to stop taking the drug, citing side effects that left them shaken, researchers report in the January issue of the journal Sleep Medicine.

Sleep paralysis — being awake but unable to move or speak — came up in 2 out of 5 (40%) reviews from people who were quitting lemborexant, researchers found.

“Felt paralyzed to move. Wanted to scream and could not make a sound,” wrote one reviewer who gave the drug a 1 out of 10. “Was able to touch my husband’s arm and waken him. He said he never saw such terror in my eyes.”

Nightmares also were reported by many of the reviewers, researchers found.

“The dreams [nightmares] are VERY vivid and that’s the reason I can no longer take this medication,” one wrote.

Lemborexant belongs to a new class of insomnia drugs that work not by broadly sedating the brain, but instead by blocking signals from the brain chemical orexin, researchers said in background notes. Orexin helps keep people awake.

For the new study, researchers analyzed 260 online reviews of lemborexant posted between 2020 and 2023 on the website Drugs.com.

About 30% of people said they’d had meaningful improvements in their sleep quality after taking lemborexant, results showed.

“One of the important messages from our study is that lemborexant was reported to work very well for some people,” senior researcher Morgan James, an adjunct assistant professor at Rutgers Brain Health Institute, said in a news release.

However, 50% of reviewers reported minimal or no perceived benefit, researchers found. About 70 of the 260 reviewers had written that they’d stopped the drug or planned to stop.

Two-thirds (68%) of reviewers reported at least one side effect from lemborexant, researchers said.

That included 32% (84) who reported vivid dreams or nightmares that disturbed their sleep and left a lasting impression on them after waking, and 22% (56) who reported sleep paralysis.

“What surprised us most was how unsettling some patients found certain side effects,” said lead researcher Abanoub Armanious, a pharmacoepidemiologist and neuropsychiatry researcher at the Rutgers University Brain Health Institute. “For these individuals, stopping the medication was not simply about it failing to improve sleep.”

These side effects might be due to the way the drug inhibits orexin, researchers speculated.

Blocking orexin can increase a person’s dream sleep, during which the brain normally switches off most of the body’s muscles, researchers said. Increased dream sleep might spill vivid dreams and muscle shutdown over into a person’s waking moments.

Not everyone reacted poorly to the side effects.

One reviewer, who rated the drug a 9, said they looked forward to their “wild crazy dreams.”

Another reviewer who gave the drug a 10 said that “I was a little afraid of the ‘sleep paralysis’ but I learned I could pull myself out of it if I wanted to.”

Researchers warned that their study can’t show how common these experiences are across all users, because people most likely to post a review tend to have very bad or very good experiences.

For example, the most common score given lemborexant on Drugs.com was a 1, followed by a 10.

But in lemborexant’s two main clinical trials, fewer than 2 in 100 participants taking it had sleep paralysis, and about 1 to 3 in 100 reported nightmares or abnormal dreams.

“A clinical trial can tell you how often side effects occur,” Armanious said. “It is less equipped to tell you how much that side effect matters to the person living it. A side effect can be rare and still be the reason someone discontinues treatment.”

Anyone taking any prescribed sleep med should talk with their doctor before stopping it or changing it, researchers said.

In the meantime, doctors prescribing lemborexant or pharmacists handing out the drug should take some time describing these potential side effects to patients, so that they aren’t taken unawares, researchers said.

“What really stands out is how different people’s experiences with this medication can be, which highlights the importance of setting expectations and finding the right treatment for the individual,” James said.

More information

The Mayo Clinic has more on prescription medications for insomnia.

SOURCES: Rutgers University, news release, Oct. 29, 2026; Sleep Medicine, January 2027

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