- a sensation of floating out of the body, which may include seeming to view the body from above;
- feelings of peace, joy or tranquility;
- a life-review in which previous life events are reviewed or relived in some sped-up manner;
- a passage through a tunnel;
- an encounter with a very bright light or a “being of light” or a light that is somehow sensed to be numinous or a source of thought or feeling;
- an experience of seeing some heavenly or supernatural realm;
- an experience of seeming to see one or more deceased relatives;
- an experience of being told that you must “go back” and continue to live your regular life;
- an experience of having heightened consciousness, mentality or perception.
Since near-death experiences were first reported, those who do not believe in a soul or life after death have been trying to suggest a natural explanation for the phenomenon. One attempt at an explanation is what we may call the "stash release" theory. This is the idea that when someone is at the verge of death or undergoing a cardiac arrest, there can be a release of hallucinogenic chemicals stored in the brain. A person may try to back up this claim by saying something like "DMT has been detected in the brain of mammals." However, there has never existed any evidence that any hallucinogenic chemicals exist in the brain of mammals other than in micro-traces a thousand times too small to produce a hallucination.
There's a new study on the topic published in a scientific journal. It is remarkable how the press release on this topic (and the NeuroscienceNews.com story based on the press release) misleadingly describe the study as if it were something supporting the "stash release" theory. The headline on NeuroscienceNews.com is " ‘Mystical’ psychedelic compound found in normal brains." The story tells us that DMT has been discovered in mammalian brains. It also says, "Her team’s work has also revealed that the levels of DMT increase in some rats experiencing cardiac arrest." But no mention is made in the story of what level of DMT was found in a mammalian brain, and no mention is made by how much the DMT level increased during cardiac arrest. You should tend to be suspicious of scientific news stories that fail to provide the relevant numbers.
Luckily the story is based on a study in a scientific journal, and the whole study can be read online here. Deplorably, the study does not reveal in its abstract what level of DMT was measured. But if you dive into the study we can get that information. The level of DMT detected was about 1 nanomole, a billionth of a mole. The paper states, "the normal rat brain contained detectable levels of DMT..ranging 0.05–1.8 nM with an average of 0.56 nM." The abbreviation nM stands for nanomole. So the study tells us that a rat brain has only about 1 nanomole of DMT.
How much is a nanomole? It's about 300,000 times smaller than the amount needed to produce a hallucinogenic result. The dose typically used to produce DMT hallucinations or a DMT "trip" is about 30 milligrams. That's a dose about 300,000 times stronger than a nanomole.
According to the site here, which can be used as a rough guide, 5750 milligrams of a particular substance is equivalent to .05 moles. So an amount 100 times smaller (about 57 milligrams) would be equal to about .0005 moles. We multiply that .0005 by a billion to get the equivalent number of nanomoles, leaving us with 500,000. So a dose of 57 milligrams is about 500,000 nanomoles, a dose of 30 milligrams is about 300,000 nanomoles, and a single nanomole is only about 1/300,000 of the minimum 30 milligrams to produce a hallucinogenic result.
According to the site here, which can be used as a rough guide, 5750 milligrams of a particular substance is equivalent to .05 moles. So an amount 100 times smaller (about 57 milligrams) would be equal to about .0005 moles. We multiply that .0005 by a billion to get the equivalent number of nanomoles, leaving us with 500,000. So a dose of 57 milligrams is about 500,000 nanomoles, a dose of 30 milligrams is about 300,000 nanomoles, and a single nanomole is only about 1/300,000 of the minimum 30 milligrams to produce a hallucinogenic result.
As for the claimed cardiac arrest increase in DMT, the paper shows that it is only an increase from 1 nanomole to 2 nanomoles. That means that even during cardiac arrest, the DMT would still be 150,000 times too small to produce a hallucinogenic result.
The news article written about the study failed to make any mention of the fact that mere nano-traces of DMT had been measured. This is not quite chicanery and deceit. It is also not quite chicanery and deceit for a man to vaguely tell his girlfriend, "I have accumulated some savings," when these savings consist merely of one penny deposited each month into a piggy bank.
See the post here for why there is a huge difference between DMT experiences and near-death experiences, and why DMT could not actually explain near-death experiences, even if it existed in the brain a million times greater than the nano-traces that have been detected.
A DMT trip is a little like this
Postscript: There's a new study indicating that near-death experiences are astonishingly common. The study is entitled “Prevalence of near-death experiences and REM sleep intrusion in 1034 adults from 35 countries.” Using a “crowdsourcing” platform to get a random sample of 1034 adults from many different countries, the study authors found that 28% of the respondents answered “Yes” when asked whether they had ever had a near-death experience.
This 28% was then asked to answer “Yes” or “No” to the following questions (called “Greyson scale questions”):
• Did
time seem to speed up or slow down?
• Were
your thoughts speeded up?
• Did
scenes from your past come back to you?
• Did
you suddenly seem to understand everything?
• Did
you have a feeling of peace or pleasantness? *
• Did
you have a feeling of joy?
• Did
you feel a sense of harmony or unity with the universe?
• Did
you see, or feel surrounded by, a brilliant light?
• Were
your senses more vivid than usual?
• Did
you seem to be aware of things going on elsewhere, as if by
extrasensory perception or telepathy?
• Did
scenes from the future come to you?
• Did
you feel separated from your body?
• Did
you seem to enter some other, unearthly world?
• Did
you seem to encounter a mystical being or presence or hear an
unidentifiable voice?
• Did
you see deceased or religious spirits?
• Did
you come to a border or point of no return?
Only those who answered “Yes” to 7 or more of these questions were judged to have had a “full-scale” near-death experience. Ten percent of the respondents answered “Yes” to 7 or more of these questions.
You may realize how remarkable such a result is when you consider that only a small fraction of the population have ever come close to death. There are no exact figures on what percentage of the population has come close to death, but a reasonable ballpark estimate might be between 10% and 20%. So it seems like a very high fraction of those who come to death experience near-death experiences.
The
scientific paper tries to suggest some causal relation between what
is called “REM sleep intrusion” and near-death experiences. REM
sleep intrusion is supposedly some state in which someone can briefly
dream while he is awake. To try to determine the level of “REM
sleep intrusion” in respondents, the scientific survey asked these
questions:
- Just before falling asleep or just after awakening, have you ever seen objects, things or people that others can’t see?
- Just before falling asleep or just after awakening, have you ever heard voices, music or sounds that other people can’t hear?
- Have you ever awakened and felt paralyzed or found that you were unable to move?
- Have you ever had abrupt muscle weakness in your legs or knee buckling, or felt sudden muscle weakness in your face or head drop?
Twenty
percent of the overall respondents answered “Yes” to three or
more of these four questions, but 34% of those who claimed to have a
near-death experience answered “Yes” to three or more of these
questions. 47% of those who were judged to have had “full-scale”
near-death experiences answered “Yes” to three or more of these
“REM sleep intrusion” questions.
The
authors have tried to play this up as something significant, but it
may have no causal significance at all. We can easily explain the
difference without imagining any causal relation between “REM sleep
intrusion” and near-death experiences.
The
“REM sleep intrusion” questions are questions about abnormal
experiences. Anyone answering the survey and reporting a near-death
experience might simply be someone more prone to candidly admit to an
abnormal experience.
In
many ways we are socially conditioned not to report abnormal
experiences, for fear of being ridiculed as an oddball. But if a
person has already admitted in a survey that he has had one type of
abnormal experience (a near-death experience), he may then be much
more likely to admit another type of abnormal experience involving
sleeping. This greater tendency to confess to a second abnormal
experience (after confessing to a first abnormal experience) can
easily explain the somewhat greater “REM sleep intrusion” scores
of people who experienced near-death experiences.
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