The Leading Scientific Theories for Near-Death Experiences, Compared

Near-death experiences are vivid and consistent enough that scientists have tried to explain them in many ways. None of the explanations has won agreement. This article lists the main ones and what the evidence says, including from researchers on different sides.

What are the main explanations?

They fall into two groups. A review in Frontiers in Psychology says the first group treats the experience as a side effect of problems in the brain. These include low oxygen or high carbon dioxide in the blood. They also include odd electrical activity, such as dream-sleep (REM) activity breaking into waking life, or seizures in the temporal lobes. The second group is psychological. It includes expectation, feeling detached from oneself or the world, and dissociation, a kind of mental distancing. Greyson’s overview adds brain chemicals, most often endorphins and a possible ketamine-like protective substance, which he calls speculative.

What is the case against low oxygen?

Greyson directs the University of Virginia’s Division of Perceptual Studies. He notes that people often assume low oxygen is behind NDEs. He argues that NDEs also happen without low oxygen, such as in illnesses that are not life-threatening. He says low oxygen usually causes confused, frightening hallucinations. He adds that studies found carbon dioxide levels normal or low during NDEs.

What about REM intrusion and the temporal lobes?

Greyson argues against both. He says the dream-sleep idea does not fit NDEs that happen under general anesthesia, which suppresses REM sleep. It also does not fit the finding of less REM sleep in people who have had NDEs. He also says NDE-like experiences are almost never seen in temporal lobe seizures. Electrical stimulation of that area usually produces fragments of music or isolated memories.

What do skeptics say?

That expectation matters, and that the experiences do not prove life after death. Psychologist Susan Blackmore wrote a chapter on NDEs for the Skeptic Encyclopedia of Pseudoscience. She lists expectation, drugs, endorphins, low oxygen or high carbon dioxide, and temporal lobe stimulation as common theories. She writes that expectation clearly has an effect. She also writes that the claim that NDEs are evidence of survival after death is untenable.

Is there a newer model?

Yes. A recent review in Nature Reviews Neurology by Charlotte Martial and colleagues was summarized by MDLinx. It found parallels between NDEs and states caused by psychedelic drugs such as DMT and ketamine. It also notes that a tendency to dissociate, and dream-sleep activity breaking into waking life, may make some people more likely to have NDEs under stress. The authors built a model called NEPTUNE. It combines the brain’s and the mind’s responses to severe stress.

Where does that leave us?

Unresolved. Greyson says the explanations lack empirical support, while others find them persuasive in part. For related findings, see What Does the Brain Experience When We Die?, and for how faiths understand these experiences, How Different Faith Traditions Interpret Near-Death Experiences.