Near-death experiences share some features with hallucinations, but they don’t fit neatly into that category. Between 10 and 20 percent of cardiac arrest survivors report vivid conscious experiences during the period when their brain showed no measurable activity. Whether these qualify as hallucinations, something more complex, or something else entirely depends on which specific features you examine.
What Makes NDEs Different From Typical Hallucinations
Hallucinations caused by brain injury, drugs, or illness tend to produce clouded thinking, confusion, irritability, and fragmented or idiosyncratic imagery. Near-death experiences look almost nothing like this. People who report NDEs consistently describe exceptionally clear thinking, a deep sense of peace, and a predictable set of elements: feeling separated from the body, moving through a tunnel or darkness toward light, encountering deceased relatives, experiencing a life review, and reaching some kind of threshold or boundary.
The clarity and consistency are unusual. Hallucinations vary wildly from person to person, shaped by the individual’s psychology, the drug involved, or the type of brain disruption. NDEs follow a remarkably stable pattern across cultures, ages, and medical circumstances. People also tend to remember them with unusual vividness for decades, unlike most hallucinations, which fade quickly or blur like dreams.
That said, most NDE features could theoretically be produced by a dying brain. Dream-like imagery, tunnel vision, feelings of euphoria: all of these have plausible neurological explanations. The sticking point, as researchers at the National Library of Medicine have noted, is that some NDEs include perceptions reportedly from outside the body that could not have been inferred from information received through ordinary senses, and that turn out to be verifiably correct. If even a fraction of those reports hold up under controlled testing, the hallucination explanation falls short.
What Happens in the Brain Near Death
A 2023 study published in the Proceedings of the National Academy of Sciences recorded the brain activity of four dying patients after ventilatory support was withdrawn. Two of the four showed a dramatic surge of high-frequency brain waves called gamma oscillations in the seconds after their hearts stopped. In some brain regions, gamma activity spiked between 2-fold and 391-fold above baseline levels. The surges were concentrated in areas associated with conscious awareness, including regions involved in processing sensory information and integrating experiences.
This matters because gamma oscillations are linked to conscious perception, attention, and memory formation in healthy brains. The fact that a dying brain can produce this kind of organized, large-scale electrical activity suggests a biological mechanism for the vivid experiences people report. The brain, rather than simply shutting down, may go through a brief period of heightened internal activity as oxygen drops.
Not every dying brain does this, though. Two of the four patients in that study showed no surge at all. This lines up with the clinical data: most cardiac arrest survivors don’t report NDEs. Only a subset of dying brains appears to generate this kind of activity, which may explain why only some people have these experiences.
Chemical Explanations: Ketamine and Natural Brain Compounds
A large-scale analysis comparing roughly 15,000 drug experience reports with 625 NDE narratives found that ketamine produced experiences most semantically similar to near-death experiences. The overlap was driven by descriptions of altered self-awareness, changes in how the environment felt, and themes related to spiritual or transcendent meaning. No other substance, out of 165 tested, came as close.
Ketamine works by blocking a specific type of receptor involved in processing sensory input and maintaining normal conscious awareness. The hypothesis is that the brain may release its own compounds with similar blocking effects when it’s under extreme stress or oxygen deprivation, essentially triggering an NDE-like state as a neuroprotective response. This remains speculative. A related idea involves DMT, a powerful hallucinogen that exists naturally in human brain tissue, but no study has confirmed that the brain releases it in significant concentrations during dying.
REM Sleep Intrusion
Another theory proposes that NDEs result from REM sleep features bleeding into waking consciousness. During REM sleep, the brain produces vivid imagery, suppresses muscle tone, and generates patterns of electrical activity similar to wakefulness. In some people, REM features can intrude during waking hours, causing visual and auditory hallucinations at the edges of sleep, along with temporary paralysis.
The overlap with NDEs is notable. The feeling of being unable to move, vivid visual scenes, and a sense of presence all appear in both REM intrusion and near-death reports. Research has found that people who report NDEs are also more likely to experience REM intrusion in everyday life. This doesn’t prove causation, but it suggests that individual differences in how the brain regulates sleep-wake boundaries may make some people more prone to these experiences.
The Oxygen and Carbon Dioxide Factor
When the brain loses oxygen, blood flow to the retina drops unevenly. The periphery of the visual field, which has a more fragile blood supply, goes dark first while the central portion stays active longer. This creates a natural tunnel-vision effect that could explain one of the most commonly reported NDE features: the sensation of moving through a dark tunnel toward a bright light. Rising carbon dioxide levels in the blood during cardiac arrest may also trigger hallucinations and feelings of detachment.
These explanations account for some elements of the experience but not others. They don’t easily explain the life review, the sense of encountering specific deceased people, or the feeling of reaching a point of no return. Oxygen deprivation also typically produces confusion and fragmented thinking, not the crystalline clarity that NDE survivors consistently describe.
Testing Veridical Perception
The strongest test of the hallucination hypothesis is whether people having NDEs can accurately perceive things they shouldn’t be able to see or hear. The AWARE II study, a prospective study across 25 hospitals, placed visual targets and played audio stimuli near patients undergoing CPR. Survivors were then interviewed about what they experienced.
The results were mixed. Of 28 survivors with some form of recalled experience, nobody identified the visual images. One person (3.5%) identified the auditory stimulus. Six of the 28 (about 21%) reported what researchers classified as a “transcendent recalled experience of death,” with features matching the classic NDE profile. The study confirmed that conscious experiences during cardiac arrest are real, but it did not produce strong evidence for perception from outside the body under controlled conditions.
Anecdotal reports of veridical perception during NDEs are far more numerous and sometimes strikingly detailed, but anecdotes are difficult to verify after the fact and are vulnerable to reconstruction bias.
Why NDEs Change People Permanently
One of the strongest arguments that NDEs are more than ordinary hallucinations is what happens afterward. People who have them undergo deep, lasting personality changes that persist for years or decades. The most commonly reported shifts include loss of fear of death, strengthened belief in an afterlife, increased compassion, reduced interest in material status, greater desire to help others, heightened appreciation for life, and deeper spirituality or sense of purpose.
Hallucinations from drugs, fever, or brain injury don’t typically produce this pattern. They might be frightening or memorable, but they rarely restructure someone’s core values. NDEs do, and not always comfortably. Some experiencers struggle with depression, broken relationships, disrupted careers, and a profound sense of alienation as their new worldview clashes with the expectations of people around them. The experience can be transformative in ways that are both positive and deeply disorienting.
Where the Evidence Stands
The honest answer is that NDEs occupy an uncomfortable middle ground. Many of their features have plausible neurobiological explanations: gamma surges in the dying brain, ketamine-like neurochemistry, oxygen deprivation effects, REM intrusion. If NDEs consisted only of vivid imagery, these explanations would likely be sufficient. But the consistent clarity of the experiences, the occasional reports of accurate out-of-body perception, and the profound long-term aftereffects don’t map cleanly onto what we know about hallucinations. Calling them “just hallucinations” oversimplifies the evidence. Calling them proof of an afterlife goes beyond what controlled studies have demonstrated. The brain clearly does something remarkable in the moments around death, and science is still catching up to what that something is.