Near-death experiences: how far can science explain them?

What people describe

A near-death experience is the term researchers use for a cluster of sensations reported by people who came close to dying, most often during cardiac arrest. Common examples include a sense of leaving the body, moving through darkness toward a light, unusual calm, a rapid review of one's life, and an encounter with deceased relatives or a compassionate presence.

The University of Virginia's Division of Perceptual Studies, where the psychiatrist Bruce Greyson began collecting such accounts in the 1970s, describes them as “intensely vivid and often life-transforming experiences” that occur under conditions — cardiac arrest, trauma, deep anesthesia — where “awareness shouldn't be possible according to conventional neuroscience.” That these reports are real, in the sense that survivors reliably describe them in consistent detail, is not seriously disputed; why they happen is the open question.

How researchers measure it

To compare reports that vary from person to person, Greyson built a standardized questionnaire in 1983 called the Near-Death Experience Scale. It scores 16 items across four groups: cognitive changes such as time distortion, emotional features like peace and joy, reported paranormal impressions, and transcendental elements such as a sense of entering another realm. Each item is worth zero to two points, a score of seven or higher counts as a near-death experience for research purposes, and the average score in one large sample of experiencers was 15.

How common it is

Not everyone who nearly dies reports one. A 2024 scoping review in Discover Mental Health that pooled 11 interview-based studies found incidence ranging from 6.3 percent to 39.3 percent of cardiac-arrest survivors, with in-hospital arrests at the low end of that range and out-of-hospital arrests clustering between about 19 and 21 percent. In the AWARE II study, the largest of its kind, roughly 40 percent of surviving patients recalled some form of consciousness during resuscitation that standard monitoring had missed.

Watching it happen: the AWARE studies

Sam Parnia at NYU Langone led AWARE II across 25 hospitals, mostly in the United States and Britain, following 567 patients who received CPR for cardiac arrest between May 2017 and March 2020. Fewer than 10 percent survived to discharge, and only 85 had usable EEG recordings during resuscitation. Close to 40 percent of those 85 monitored patients showed spikes of brain activity linked to higher mental function — gamma, delta, theta, alpha, and beta waves — sometimes as long as an hour into CPR. Parnia said the recalled experiences were “different from hallucinations, delusions, illusions, dreams, or CPR-induced consciousness.”

A surge before the end

In 2013, Jimo Borjigin's team at the University of Michigan placed electrodes in nine rats and induced cardiac arrest. Within 30 seconds, every rat's brain produced a burst of highly synchronized activity; a co-author, George Mashour, said the electrical signatures of consciousness “exceeded levels found in the waking state.” It was the first study to give the phenomenon a measurable neural basis.

A decade later, Borjigin's group recorded four dying, comatose patients in hospital. Two of the four showed a surge of gamma waves, concentrated at the temporoparietal junction where the temporal and parietal lobes meet, within 30 seconds to two minutes of the ventilator being removed. Borjigin said the pattern resembled brain activity seen in wakefulness or dreaming.

Physiological explanations

Several biological processes converge in a dying brain. Oxygen loss triggers an initial burst of activity before slower waves take over and the EEG eventually flattens; the final cascade of misfiring neurons has been described as a “triphasic wave of death” by Dr. Ajmal Zemmar, a neurosurgeon. A 2024 scoping review also found that one small study recorded significantly higher carbon dioxide levels in patients who later reported a near-death experience, and that REM sleep intruding on waking consciousness has been linked to similar experiences.

The researcher Charlotte Martial has proposed that a mix of chemical signals could shape what people feel as oxygen runs short: serotonin contributing to vivid imagery, endorphins to the sense of peace, noradrenaline to how sharply the episode is later remembered. Separately, the neuroscientist Christof Koch has pointed to reduced blood flow reaching the outer retina first, which may explain the tunnel-like narrowing many survivors describe.

What the explanations do not cover

None of this settles the matter. The neurologist Daniel Kondziella has argued that gamma surges may be “aberrant electrophysiological activity” rather than evidence of conscious experience, and because Borjigin's four hospital patients did not survive, no one could ask what, if anything, they felt. Koch has written that it remains “mysterious” why a dying brain would register its own shutdown as blissful rather than frightening. A 2017 University of Virginia study that Greyson co-authored found experiencers recall the episode as “realer than real” compared with actual or imagined memories, a quality no explanation yet accounts for.

Where the science stands

Two conclusions can be kept separate. That people survive cardiac arrest with vivid, consistent, well-documented memories is no longer seriously disputed; the Greyson Scale, AWARE II, and independent surveys agree on that much. What causes them is not settled — oxygen loss, gamma surges, REM intrusion, and shifting neurotransmitters each explain some reported features but not all of them, and researchers who study the same data still disagree about whether awareness briefly persists after the heart stops or the brain is only staging a final, disordered performance. Real or Legend files this record as disputed, not because the reports are doubted, but because their cause is not yet agreed.

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