It's just your brain going haywire. Kinda like taking hallucinogens.

Been there twice still not convinced.

I strongly suspect that there are causes for near death experiences, specifically being near death!

I think that the fact that such experiences can be created by neurosurgeons poking around in your brain is fairly strong evidence that it is nothing to do with the supernatural or evidence for life after death. People want to believe in it so they do.

Had one. Carl Sagan's book, "Demon Haunted World" explained it to my satisfaction.

Any totally subjective experience which is, by its nature, untestable and unrepeatable by anyone, even including the original ‘observer’, cannot be considered as evidence for anything in any circumstances.

The interesting part about NDE's is the stories where people describe in detail things going on in other rooms while they were flatlining. Things which they could have had no way of observing, even if fully conscious.

Lack of oxygen

I had one. Well, I definitely was out of my body; I don’t believe I was dead.
It was during the delivery of my daughter, my second child. The labor was rapid and violent: I had about 5 contractions and felt the urge to push. I recall the florescent lights going by above my head as they ran me to delivery(1982, separate room for each stage); everything was very blurry because I’m near-blind-nearsighted, and my glasses were still in the labor room. I recall looking up from the delivery table, very briefly...then, suddenly, I was in the upper right corner of the room, looking down. I saw the back/head of the doctor, instrument table to his right; the nurses around the infant warmer, getting things from a cabinet in the back of the room(behind the head of my body). There I was, on the table, and the baby’s head was almost crowning; the doctor had one hand on it. I was bleeding heavily(turned out I lost two units)....I was very calm. I could see perfectly, every detail. There was no noise, but I understood what was happening.
No tunnel, lights, or any of that, but I was not afraid. I thought: that’s MY baby. That’s ME.
Then I was back in my body on the table, all my noisy and blurry, and I was in tremendous pain. Like fire in my whole body. The baby was out and they were working on the hemorrhage(doctor said I had a partial placental abruption, which explains the bleeding, severe pain, and rapid labor). I was screaming, so they gave me something and I calmed down.

It was years before I thought much about this. I later worked as an RN in that unit, and the room was exactly as I recalled. I think the pain, trauma, and blood loss caused my brain to dissociate for a few minutes. I’m kind of glad it did.

I think that, as the body draws close to death, the brain begins to do some very strange things as various processes slow down and are disrupted - that's likely to leave you with some pretty odd left-overs if you're then brought back from the edge.

When does near-death or death occur? Science cannot determine with certainty exactly when death occurs. We do know however, that the human brain is capable of very vivid hallucinations. We also know that believers' near death experiences precisely reflect their beliefs about an after life. Isn't it odd that Muslims experience an Islamic version of the afterlife, while Christians meet Jesus, and Hindus experience whichever version of the Hindu afterlife they expect?

What do famous authors and their views have to do with anything? Appeal to authority is a logical fallacy.

No, NDEs don't interfere with atheism, but believing in them conflicts with reality and reason.

Bah Humbug! Died 2 times...once from strangulation by ex hubby, once from a stroke.
First time just worried sick about my baby as I passed out. S3cond time, so nice & peaceful, and pain-free, and no memory of former life....came back to lots of pain, pain, lots of residual side effects from the stroke, fear, worry, etc.

"First, Alexander claims that his “cortex was completely shut down” and that his “near-death experience ... took place not while [his] cortex was malfunctioning, but while it was simply off.” In King's green room, I asked him how, if his brain was really nonfunctional, he could have any memory of these experiences, given that memories are a product of neural activity? He responded that he believes the mind can exist separately from the brain. How, where, I inquired? That we don't yet know, he rejoined. The fact that mind and consciousness are not fully explained by natural forces, however, is not proof of the supernatural. In any case, there is a reason they are called near-death experiences: the people who have them are not actually dead.

Second, we now know of a number of factors that produce such fantastical hallucinations, which are masterfully explained by the great neurologist Oliver Sacks in his 2012 book Hallucinations (Knopf). For example, Swiss neuroscientist Olaf Blanke and his colleagues produced a “shadow person” in a patient by electrically stimulating her left temporoparietal junction. “When the woman was lying down,” Sacks reports, “a mild stimulation of this area gave her the impression that someone was behind her; a stronger stimulation allowed her to define the ‘someone’ as young but of indeterminate .”

Sacks recalls his experience treating 80 deeply parkinsonian postencephalitic patients (as seen in the 1990 film Awakenings, which starred Robin Williams in a role based on Sacks), and notes, “I found that perhaps a third of them had experienced visual hallucinations for years before l-dopa was introduced—hallucinations of a predominantly benign and sociable sort.” He speculates that “it might be related to their isolation and social deprivation, their longing for the world—an attempt to provide a virtual reality, a hallucinatory substitute for the real world which had been taken from them.”

Migraine headaches also produce hallucinations, which Sacks himself has experienced as a longtime sufferer, including a “shimmering light” that was “dazzlingly bright”: “It expanded, becoming an enormous arc stretching from the ground to the sky, with sharp, glittering, zigazgging borders and brilliant blue and orange colors.” Compare Sacks's experience with that of Alexander's trip to heaven, where he was “in a place of clouds. Big, puffy, pink-white ones that showed up sharply against the deep blue-black sky. Higher than the clouds—immeasurably higher—flocks of transparent, shimmering beings arced across the sky, leaving long, streamerlike lines behind them.”
[scientificamerican.com]

They are NEAR death experiences, not death experiences.