Many clinicians will understandably dismiss a patient’s report of a vivid, frightening dream about falling ill as a byproduct of anxiety. However, a growing body of neurobiological research suggests these nocturnal narratives may be more than mere coincidence. Emerging evidence indicates that some dreams may serve as harbingers of disease, detecting physiologic changes before conventional diagnostics — or even symptoms — emerge.
Unlike typical dreams that fade upon waking, “prodromal dreams” stay with people and involve vivid, often disturbing imagery in which they discover a specific illness. Anecdotal examples from the International Association for the Study of Dreams include a woman who dreamt of her aunt, who had died of breast cancer, warning her that she too had the disease — later confirmed by mammogram.
Now, new neuroscientific models and clinical studies are beginning to provide biological plausibility for how the sleeping brain might detect early pathology.
A 2025 hypothesis and theory paper in Frontiers in Psychiatry, for example, proposes that some prodromal dreams emerge from interoceptive predictive processing during REM sleep. During REM, limbic and paralimbic regions involved in interoception compress high-dimensional visceral and autonomic inputs into low-dimensional summaries. When these summaries diverge from the brain’s predictions, a “prediction error” is generated. Because REM operates in a hallucinatory, hyper-associative mode with reduced external input, the brain’s attempt to explain that error is rendered as vivid, often threat-laden or metaphorical dream imagery that can foreshadow emerging pathology.
“In neurodegenerative conditions, such as Parkinson’s disease and Alzheimer’s disease, it is possible that changes to brain networks involved in dream generation and emotional tone may cause changes to dreaming years or decades before other symptoms of the disease emerge,” Abidemi Otaiku, MD, clinical research fellow at UK Dementia Research Institute, Imperial College London, London, England, told Medscape News Europe.
Early Warning in Disease
Research is revealing a possible connection between dreams and neurodegeneration in Parkinson’s disease, where dream-related symptoms can emerge years before motor dysfunction. Isolated REM sleep behavior disorder (iRBD) — in which people physically act out their dreams while having no overt neurologic disease — often emerges years before motor symptoms appear, according to a 2025 review in the Journal of Sleep Research. The predictive power of this phenomenon is sobering: a 2019 meta-analysis tracking nearly 4000 patients with iRBD found that about one third had developed Parkinson’s disease or dementia with Lewy bodies after an average of 5 years, with statistical modeling estimating this proportion would exceed 90% by 14 years. A smaller subset may develop multiple system atrophy.
These clinical observations now have a biological correlate. A 2025 Brain Communications study used advanced MRI to detect excess iron accumulation in the substantia nigra — a small but critical movement hub — in people with early Parkinson’s disease. Those with dream enactment showed iron levels intermediate between healthy control individuals and patients with Parkinson’s disease, and iron deposition increased measurably over 4 years. This suggests that dream enactment can coincide with subtle, yet detectable, brain changes that precede clinical diagnosis.
The genetic architecture of this subtype is equally revealing. A 2025 international genetics study comparing patients Parkinson’s disease with and without RBD uncovered distinct patterns at two pivotal genes: SNCA and LRRK2. This genetic fingerprint points to an alpha-synuclein-related subtype in which dream enactment may be woven into the disease pathway from its earliest stages. A 2023 review in Cell Death and Disease additionally reports that when RBD accompanies Parkinson’s disease, the disease typically follows a more aggressive trajectory, with faster progression and higher rates of cognitive decline, hallucinations, depression, and anxiety.
Otaiku’s own research includes a study that found frequent and distressing dreams are associated with an increased risk for Parkinson’s disease if the dreams occurred within 5 years prior to diagnosis. “My work has mostly been about nightmares as a prodromal sign in neurodegenerative diseases,” Otaiku said. “I think nightmares could be used alongside other prodromal symptoms like loss of smell, depression, and dream enactment to facilitate early detection.”
When Patients Report Prodromal Dreams
If a patient reports having prodromal dreams or aggressive nightmares, what should clinicians do? A sleep study may be warranted to differentiate prodromal dreaming from other sleep disorders. Nightmares and dream enactment are treatable, and evaluation can uncover conditions such as RBD, obstructive sleep apnea, or medication effects.
Some patients may report upsetting dreams to their physician and express a desire to stop them. “It is possible to wake yourself up from a dream, and there are those who may do so during a distressing one,” explained Anthony Bloxham, PhD, lecturer in psychology and member of the Sleep Research Group at Nottingham Trent University, Nottingham, England. “Lucid dreaming is all about recognizing when you are dreaming, and then maybe taking more active control of the dream as it unfolds.”
However, in the case of a prodromal dream, waking up may be counterproductive because important details may be lost. “Confronting whatever is bothering you in the dream, understanding it, and trying to change it into something positive or more pleasant seems a more problem-solving focused approach than simply trying to escape,” Bloxham told Medscape News Europe.
If a patient expresses fear or discomfort about their dreams, reassurance is important. Ensure the patient understands that a dream is not necessarily indicative of a diagnosis, but that you would like to gather more information.
“My advice would be to keep the topic light,” said Brigitte Holzinger, PhD, professor and scientific director of the postgraduate sleep coaching program at the Medical University of Vienna, Vienna, Austria. “Call it an experiment — ask if the patient would be interested in participating,” she told Medscape News Europe. Ask the patient to keep a dream journal, noting details as soon as they wake up. Even an incidental part of a dream may be a valuable clue.
Finally, a full medical workup is warranted if there is enough evidence to suggest a suspected illness.
Otaiku, Bloxham, and Holzinger reported no relevant financial relationships.
https://www.medscape.com/viewarticle/are-your-patients-bad-dreams-predicting-disease-2026a10000ff
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