A posting at Scientific American has taken the time to aggregate all of the scientific findings on near death experiences (NDEs). As this is a big deal for the skeptic community, I though that I would summarize the evidence for you here, for resource purposes.
The Science of Near-Death
Although only approximately 3% of Americans declare to have had a near-death experience, their seemingly paranormal components have perpetuated pseudoscience for years. Until now.
You DO NOT have to be actually dying to have them
One study showed that out of 58 patients that reported experiencing “unusual” experiences associated with NDEs, 30 of them were not actually in any danger of dying, although they thought they were.
The scientific assumption is that there is a biological underpinning to all of the effects experienced by those who have NDEs. Therefore, taking this study into consideration, we could come up with a plausible account for why people only have to think that they are dying, and not be actually in danger, to have these experiences.
Death is a scary thing. We could imagine the body having a response mechanism to such fear, such as producing chemicals in the brain that calm the individual and produce euphoric sensations, so that the individual experiences less trauma. This is an artifact of how the brain is evolutionarily wired. If we truly believe that we are going to die, with the accompanying dread, it is very possible that the brain will produce the same calming effects. This may sound like speculation, but as we will see below, it is supported by evidence.
The evidence shows that most people who are dying do not even experience a NDE. Large scale studies showing the number of people who report NDEs show that a large proportion (82%) of near-death survivors do not report near-death experiences. Furthermore, around half of the people who reported near-death experiences in these studies were not in danger of dying.
You do not have to be, in reality, dying to go through a NDE. Even if you are dying (but survive), you probably won’t have one. This contradicts the notion that NDEs are the hallmark of your spiritual passing over. This evidence speaks to a purely physical phenomenon, brought on by fear and grounded in neurology, not anything paranormal.
People who have had NDEs felt like they were dead
I’m sure they did but this experience is not even limited to them. Patients with Cotard or “walking corpse” syndrome hold the delusional belief that they are deceased. This disorder has occurred following trauma, such as during advanced stages of typhoid and multiple sclerosis, and has been linked with brain regions such as the parietal cortex and the prefrontal cortex.
If experiencing yourself as a corpse is explained by damage or alterations to your brain, a purely physical cause, it is then extremely unlikely that the exact same effect is produced by something paranormal. Why invoke an explanation that requires so many more assumptions to be true and so much more science to be overturned? Following Occam’s Razor, the natural explanation suits us just fine.
Science can explain out-of-body sensations
Quoting from Scientific American:
Out-of-body experiences are now known to be common during interrupted sleep patterns that immediately precede sleeping or waking.For instance, sleep paralysis, or the experience of feeling paralyzed while still aware of the outside world, is reported in up to 40 percent of all people and is linked with vivid dreamlike hallucinations that can result in the sensation of floating above one’s body. A 2005 study found that out-of-body experiences can be artificially triggered [emphasis mine] by stimulating the right temporoparietal junction in the brain, suggesting that confusion regarding sensory information can radically alter how one experiences one’s body.
Being that out-of-body experiences can be triggered remotely from inside your brain leads us to the obvious conclusion: it is all in your brain. You don’t even have to be dying!
People may feel like they are outside of their own bodies, but they are merely remembering memories of the room, and not experiencing it in real-time as a “floating spirit.” For example, Dr. Penny Sartori placed playing cards in obvious places on top of operating room cabinets at a hospital in Wales in 2001, while she was working as a nurse, as part of a supervised experiment. Although she’s a believer in the afterlife, and documented fifteen cases of reported out-of-body experiences by patients during her research, not one person ever reported seeing the playing cards or even knowing they were there. We would expect differently if patients were actually floating around up there.
Trauma can have severe effects on your brain. Your own sense of where you body is in space is a complex construction of sensation and cognition. When this sense is affected by trauma, such as being close to death, many “weird” things may be felt. Imagine if instead of locating “you” somewhere behind your eyes, trauma in your brain caused that location to be switched to the bottom of your feet. This would surely feel “out-of-body” and go beyond anything we have ever experienced before. This confusion is at the root of this experience.
Science can explain the sight of loved ones during NDEs
Again, quoting from Scientific American:
A variety of explanations might also account for reports by those dying of meeting the deceased. Parkinson’s disease patients, for example, have reported visions of ghosts, even monsters. The explanation? Parkinson’s involves abnormal functioning of dopamine, a neurotransmitter that can evoke hallucinations [emphasis mine]. And when it comes to the common experience of reliving moments from one’s life, one culprit might be the locus coeruleus, a midbrain region that releases noradrenaline, a stress hormone one would expect to be released in high levels during trauma. The locus coeruleus is highly connected with brain regions that mediate emotion and memory, such as the amygdala and hypothalamus.
During an NDE you may be “seeing” loved ones, but the evidence shows that these meetings are constructs of memory evoked during stress. As in the other explanations, if a chemical in your brain can produce the exact same effects, the paranormal explanation is no longer plausible.
The benefit of seeing your loved ones or reliving your life is the calming effect that it produces. Evolution, as one possible explanation, may have selected for this so that during times of high stress you brain secretes hormones and chemicals in order to bring about this calm. It makes sense, paranormal ghost contacting does not.
Near-death experiences are not unique
Research has found that recreational drugs produce similar effects as NDEs. Drugs such as ketamine can also trigger out-of-body experiences and hallucinations. Ketamine affects the brain’s opioid system, which can naturally become active even without drugs when animals are under attack, suggesting trauma might set off this aspect of near-death experiences.
Insights like this again lead us to the conclusion that our brain is producing certain chemicals that give us these experiences.
But I saw a bright white light at the end of a tunnel!
Tunnel vision can occur when blood and oxygen flow is depleted to the eye, as can happen with the extreme fear and oxygen loss that are both common to dying. This sensation is also linked to having high levels of carbon dioxide in the brain, which is why many people who have not been in danger of dying have experienced this tunnel vision.
Quoting Scientific American:
Altogether, scientific evidence suggests that all features of the near-death experience have some basis in normal brain function gone awry [emphasis mine]. Moreover, the very knowledge of the lore regarding near-death episodes might play a crucial role in experiencing them—a self-fulfilling prophecy.
It makes no sense that people don’t have to be dying to have a NDE, or that not every dying person experiences an NDE, or that drugs and chemicals exactly mimic NDEs, or that brain trauma produces similar effects, if the supernatural “crossing-over” theory is correct.
We have a scientific explanation for every component of the near-death experience. But this does not diminish its importance to us, as the experience itself has had profound, life-changing results on people. However, proceeding with the debunked notion that a near-death experience shows you the “other side” or Heaven or the afterlife is to proceed in ignorance of science.
It is surely an interesting phenomenon, and plays to our emotions and our beliefs, but is absolutely of this world.