When Isabella Cavallo was in college, she started having a series of panic-inducing dreams. “I had so many nightmares about getting kidnapped or running away from a stranger who was trying to attack me,” says Cavallo, an editor in New York. “One of my recurring dreams was that I was driving with a friend, and then the car would crash and we were being chased by a stranger who was trying to kidnap us,” she says.
A few years after these haunting dreams began, other strange things started happening: Weird cramps and pains developed in Cavallo’s side and kept getting worse, and a bad case of cystic acne, which had never been a problem before, cropped up on her face. She went to her gynecologist to figure out what was going on—a test for HPV came back negative, but a Pap smear showed some abnormal cells, so her doctor ordered a biopsy and an MRI.
A few months later, at only 21, she was diagnosed with stage 2 cervical cancer. After two surgeries, and now 25, she is fully recovered, and even ran a marathon recently. “Back then, I didn’t think much about those dreams, but now I really wonder if my brain was trying to warn me,” she says.
Meet Our Experts: Patrick McNamara, Ph.D., professor of psychology at National University and associate professor of neurology at Boston University School of Medicine; Marc Milstein, Ph.D., host of the Best of Your Brain podcast and author of The Age-Proof Brain; Sneha Mantri, M.D., chief medical officer of the Parkinson’s Foundation.
Predictive Dreams?
It’s possible that these dreams were a warning. As sci-fi (or perhaps woo-woo) as it sounds, there is solid, scientific reasoning to support the idea that dreams like Cavallo’s can sometimes be early warning signs that something is off with your health.
Known as prodromal dreams, “these types of dreams can indicate the onset of an illness before there are any classical medical signs that a disorder is coming on,” says Patrick McNamara, Ph.D., professor of psychology at National University and associate professor of neurology at Boston University School of Medicine (he adds that dreams can also be considered prodromal if they occur after unexplained symptoms appear, but before you have a diagnosis.)
In a paper he published in Frontiers in Psychiatry last year, McNamara pointed out that prodromal dreams have been documented in various research studies for gastrointestinal, pulmonary, gynecological, and arthritic illnesses, as well as autoimmune disorders, cognitive decline, and psychiatric disorders such as bipolar.
Of course, the vast majority of our dreams—even the nightmares that make us wake up in a sweaty panic—are just dreams, not harbingers of illness, serious or otherwise. We have these and other extremely vivid dreams with spookily interpretable storylines for all kinds of reasons, including stress, anxiety, poor sleep, even that spicy tuna bowl you snarfed down a little too close to bedtime. People experiencing post-traumatic stress disorder (PTSD) or bereavement can have vivid and disturbing dreams; medications designed to ease your mind and/or help you sleep, such as antidepressants, melatonin, sleeping pills such as Ambien, can also affect how you act and what you see when you sleep.
Still, if your dreams start to drastically change in certain ways, pay close attention. “Step one is to take your dreams seriously,” says McNamara. “Step two is to bring them up to your primary care physician.”
Here’s a closer look at what may be going on:
An evolutionary clue
Way, way back, before there were MRIs, CT scans, and blood tests to help diagnose disease, there were dreams. In ancient Greece, Mesopotamia, and China, for example, healers often looked to their patients’ nocturnal visions for clues to their ailments.
That mostly ended with the advent of modern science, but it doesn’t mean those old-school dream interpreters weren’t onto something. “All human beings have very sensitive threat detection circuits in their brains that pick up very faint signals from the body that something is wrong,” McNamara explains. “That threat detection center then can send a highly compressed signal to the brain that may (or may not) get picked up in your dreams.”
These faint but very real SOS signals can sometimes be heard by the subconscious brain weeks, months, or even years before the waking brain ever gets the message. “Our brains are constantly monitoring what’s happening in the body, but during the day we’re often distracted and focused outward,” says neuroscientist Marc Milstein, PhD, host of the Best of Your Brain podcast and author of The Age-Proof Brain. “But when we’re sleeping, your brain continues to process physical and emotional information that we may not have fully registered while awake.”
During sleep, the brain weaves together emotional, physical, and psychological inputs into narratives. “Dreams aren’t literal messages, but they can sometimes reflect stress or changes that deserve attention,” says Milstein. This process happens primarily in REM sleep, the stage when the most vivid dreams always occur (REM stands for rapid eye movement—your eyes dart around as you watch your dreams play out).
This is also the phase of sleep when the threat detection circuits in your brain are highly activated, picking up those signals from the internal body sensors, such as the amygdala and prefrontal cortex, McNamara says. These circuits don’t necessarily know specifics—merely that your homeostatic set points, or a sense of balance in your body, are awry. When the balance is off, infection-fighting T cells, for example, become activated, and a signal is relayed that something is wrong, even if it doesn’t know why the T cells are on on the case.
What are prodromal dreams like?
There is no specific content that defines a prodromal dream, says McNamara, and they are almost always metaphorical and so need interpreting. But there are a few types we know about:
General dreams of being threatened: “I was running down the stairs, being chased by a group of men I didn’t recognize”
A common theme is being chased or threatened by an animal or a male stranger, McNamara says. These dreams can be vivid, or you may not even remember exactly what happened as you wake up in a sweaty panic with your heart racing. “It’s really about detecting a threat,” he adds.
But why does the aggressor tend to be a stranger rather than, say, that kid who bullied you in third grade or your nasty old boss? Evolutionary psychology. “We know from 40 years of studies about dream content that strangers indicate a threat,” McNamara explains. From the earliest paleolithic days of humankind, he says, tribal conflict has been one of the greatest threats to our life.
Threatening, unusual, and exceptionally vivid nightmares often begin before the onset of a mental health condition, including bipolar disorder, depression, and schizophrenia. (A recent study, for example, found that 59% of people with bipolar disorder experienced sleep disturbances in the weeks leading up to a manic or depressive phase, and 44% had parasomnias, which includes disturbing dreams.)
Specific, predictive dreams: “I kept hearing someone whisper, ‘You have cancer…’”
Every once in a while, a dream takes the message one step further with specific, detailed clues: Perhaps the most well-known example of this was when the Avengers actor Mark Ruffalo went to sleep one night and dreamed he had a brain tumor: “It wasn’t even a voice, it was just pure knowledge: You have a brain tumor and you have to deal with it immediately,” he later told the hosts of the podcast Smartless. He saw his doctor the next day, who ordered an MRI, which revealed a large but benign tumor behind Ruffalo’s ear. He had surgery to keep it from growing. In another case, McNamara says, a Russian physician wrote about a patient who dreamed of being shot in the chest, then later died of a heart attack.
These more precise dreams may involve a combination of the subconscious signals and a few actual physical symptoms that may not have seemed important on their own (Ruffalo says he had an earache the night before his prophetic dream.)
A few studies have tried to suss out what’s going on: In a 2015 survey of 18 women who say they had prodromal breast cancer dreams, most said the dreams were extremely vivid and included a feeling of being attacked or menace—that is, generally threatening dreams, such as the ones mentioned above. Still, 44% of the dreams specifically involved the words “breast cancer” or “tumor.”
The above small survey demonstrates that some women can have nightmares, sometimes about getting breast cancer, before being diagnosed. The converse, however, does not follow—most women with breast cancer do not have such dreams. In a follow-up 2020 study by the same author, an anonymous survey of 163 women undergoing breast biopsy found that only 1 reported having a dream that compelled her to ask for a breast cancer screening.
And in another case of the dreamscape reflecting an imminent health crisis, researchers have found a striking connection to dreams and suicide attempts: A 2023 study of 40 people in a psychiatric emergency department following suicide attempts found that 80% had experienced nightmares, some of them suicide-themed, within three months preceding their own attempt. Recurrent distressing dreams, especially when they’re intense or escalating, shouldn’t be ignored, says Milstein, adding that they should be a signal that someone is under significant psychological strain and may benefit from professional support.
Acting out dreams: “I kicked my partner so hard, I was afraid I broke her back”
The condition in which people seem to have the most prodromal dreams is Parkinson’s disease (PD), the progressive, neurodegenerative disease that affects movement and, eventually, cognition. It’s estimated that between 33-46% percent of people with Parkinson’s experience a sleep disorder called REM sleep behavior disorder, or RBD, in which they have dreams that they act out physically while they’re asleep, years or even decades before other symptoms appear.
John Poma, a 61-year-old lawyer in Virginia, had his first prodromal dream in the summer of 2018. “I literally attacked my wife in my sleep,” he recalls. “She went flying off the bed and ended up on the floor. When I woke up, I was just dazed, and she asked me, ‘What the heck are you doing?’ I remembered that I had a dream where I was being attacked and I was defending myself, but I had no idea that I had actually attacked her.”
After this happened a few more times, and Poma grew increasingly concerned about injuring his wife, he made an appointment with a sleep disorders specialist, who diagnosed him with RBD. The doctor also noticed he had a slight tremor and referred him to a movement disorder specialist. “He said, ‘You don’t have Parkinson’s disease now, but you are at risk for developing it,” Poma recalls.
This is true of anyone with RBD, as the vast majority go on to develop Parkinson’s. Here’s the connection: In REM sleep, when the most vivid dreams occur, the body normally goes into a paralyzed state to protect you from acting out your dreams, says Sneha Mantri, M.D., chief medical officer of the Parkinson’s Foundation. “But one of the early changes that happens for people with Parkinson’s is that protein deposits called Lewy bodies start to form in the part of the brain that controls sleep paralysis, so they start to move around when they’re dreaming,” she explains.
Other recent studies have found that in addition to physically active dreams, frequent, disturbing dreams/nightmares in the five years prior to diagnosis are related to a greater risk for developing PD and a more rapid decline in motor and cognitive skills in PD patients, possibly due to structural changes in the brain.
What should you do if you are having recurrent disturbing dreams?
First, remember that we all have bad dreams every now and then, even the same ones over the years. They could be about stress at work, that infuriating news story you scrolled by just before you fell asleep, a side effect of medications or lack of sleep. Those are normal, and don’t necessarily mean anything.
And even in conditions for which there is documented evidence of prodromal dreams, that doesn’t mean any given dream is a warning—there are many online message boards with women describing their dreams of having breast cancer, for example, and very few of those turn out to be predictive. These dreams may simply represent a generalized fear of the cancer, or a “worry dream,” says McNamara. As of yet, it seems that no one has studied how many of these predictive dreams actually turn out to be correct.
If you’re prone to dreams in which you’re being chased or haunted or find yourself restlessly moving about during sleep, Milstein suggests you consider what you’re doing before bed. “Reducing stress in the evening, whether that’s limiting upsetting news or practicing relaxation techniques, can help create a calmer sleep environment and may reduce the likelihood of distressing dreams,” he says.
If the dreams persist, pay attention to their content, suggests McNamara. “If you’re being chased, that’s one thing. But if you’re being chased and there’s also a large number of strangers in the dream, and you dream you just got shot in the chest, now there are three different prodromal indicators,” he says. If you notice a meaningful change in your sleep or dreams, it’s reasonable to mention it to your doctor as part of a broader health conversation, adds Milstein. “It doesn’t mean something is seriously wrong, but patterns in sleep can sometimes offer useful clues,” he says. This also may spur a conversation with your doc about reviewing any medications you may be on to see if you’re having side effects. They also may suspect that you have anxiety or possible PTSD, and refer you to a therapist, as these conditions often include bad dreams.
There’s no downside of deploying these potentially powerful warning signs. “Dreams are key to early identification for Parkinson’s, because it is such a classic early symptom,” Dr. Mantri says. “That’s an opportunity to make lifestyle changes around diet and exercise to reduce your risk of developing Parkinsonism down the line.” John Poma started an intense exercise program as soon as he was diagnosed with his REM sleep disorder, and though he did get officially diagnosed with Parkinson’s in 2022, he believes his disciplined exercise routine has helped keep his physical symptoms at a level—for now—with minimal disruption to his daily routine. (Research has shown that exercising at least 2.5 hours per week can improve physical and emotional well-being as well as slow the progression of symptoms, according the Parkinson’s Foundation.)
Disturbing dreams can also provide an opportunity to address any serious mental illnesses early on: “If someone has a personal or family history of mental illness and begins experiencing new or worsening nightmares, it’s important to discuss with a psychiatrist,” says Milstein. “Early intervention in mental health tends to improve long-term outcomes.”
Experts hope to learn more about prodromal dreams in the future. “We should learn how to capture that information and content to see if it can be used to prevent preventable disorders or to begin treatment in the earliest stages,” says McNamara. Milstein is optimistic: “As technology advances, tools like AI may eventually help researches analyze complex patterns linking sleep, mood, and health. We’re still in the early stages of understanding that relationship, but it’s an area worth studying,” he says.
Remember: The odds are fantastic in favor of your dream signaling you’re way overdue for a a vacation somewhere peaceful. As for Isabella Cavallo, whose dreams preceded her diagnosis, her cervical cancer was caught early, and she says she is “totally fine” now. “But best of all, I don’t have any of those scary dreams anymore,” she says.
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