Most people experience nightmares or vivid dreams from time to time, especially during periods of stress, anxiety, or major life changes. But experts suggest that certain unusual or intense dreams could signal more than just worry—they may indicate an impending illness, even before any physical symptoms appear.
Psychologists refer to these as “prodromal dreams,” occurring when the brain detects subtle biological changes in the body at the earliest stages of illness. The theory is that as infections or other health disturbances begin, the body sends faint internal signals to the brain, which are then processed during REM sleep—the stage when dreaming is most vivid.
These signals are thought to be interpreted in paralimbic regions of the brain, such as the amygdala and anterior insula, which are responsible for detecting threats. The brain may then translate these early warning signs into symbolic or unsettling imagery in dreams, creating what appear to be alarming or unusual scenarios long before a person shows overt symptoms.
Professor Patrick McNamara, a sleep psychologist at Boston University School of Medicine, explains, “The brain constantly monitors signals from the body to maintain physiological balance. During REM sleep, it synthesises these signals, creating a kind of snapshot of what’s happening inside the body.”
Dreams as indicators of illness are not a new idea. In Ancient Greece, patients would sleep in Asklepieia temples hoping for healing dreams. Modern research is now attempting to identify the biological mechanisms behind these experiences. McNamara’s recent study in the journal Frontiers explores how dreams might act as early alerts for health issues.
Evidence supporting this theory comes from studies of neurological conditions such as Parkinson’s disease and dementia. A 2017 study of over 1,200 people with REM sleep behaviour disorder—a condition where people physically act out dreams—found that 73% were diagnosed with Parkinson’s or dementia within 12 years of their first dream disturbances. Similar patterns have been observed in other illnesses, including gastrointestinal, respiratory, gynaecological, dental problems, and arthritis.
Some studies even suggest that prodromal dreams could appear before serious illnesses such as cancer. A 2015 study reported that women who later developed breast cancer had vivid, intense, or unusually realistic dreams prior to diagnosis. McNamara also notes that prodromal dreams can occur with minor illnesses such as colds or the flu.
According to McNamara, recurring themes may indicate a looming health issue: unusual aggression directed at the dreamer, the presence of mildly threatening male strangers, or insects appearing in dreams may all act as symbolic warnings. A 2022 study examining 2,888 dreams before COVID-19 diagnoses found frequent references to maggots or snake bites.
Dream analysts also report anecdotal evidence. Theresa Cheung, who runs ITV’s Your Dreams Explained, says she receives countless messages from people claiming that dreams helped them detect serious health problems. One woman described a dream of a shadowy figure pointing at her breast, which led her to seek medical attention and discover stage-three cancer.
While the theory is still largely speculative and requires further research, it could have potential applications in healthcare. For example, monitoring dream changes in high-risk mental health patients might provide early warnings for suicidal ideation. A 2022 study found that 80% of patients who later attempted suicide experienced altered dreams in the months prior. McNamara envisions a future where AI could record and analyse dreams, alerting healthcare providers to potential risks.
Although practical use remains distant, the concept of prodromal dreams highlights the brain’s remarkable ability to detect subtle changes in the body—sometimes long before traditional medical tests can.
