This is from Near-Death Experiences: A Neurophysiologic Explanatory Model by
Melvin L. Morse, M.D.
David Venecia, Jr., M.D.
Jerrold Milstein, M.D.
in the J. of Near Death Studies, fall 1989, p. 50
We searched the medical literature without success for other agents
or psychological processes that could cause NDEs or OBEs. For example,
studies of hypoxia, other hallucinogens, psychotic conditions, or
intensive care unit stress syndromes do not produce NDEs. One study
described a complex hallucination in a patient on narcotics, reversed
by naloxone (Judson & Wiltshaw, 1983). Careful review of that patient's
experience revealed that it lacked most of the descriptive elements
of NDEs, including an OBE, and that the patient was semiconscious
during the experience. Although that case has been cited as
clinical evidence that perhaps endorphin systems are involved with
NDEs, it is unlikely that that patient had an NDE. Naloxone, which
the patient was treated with, has been well documented to cause very
similar hallucinations, including a sense of soullessness and paranoid
ideation. These elements, which are seen in drug-induced hallucinations,
are not seen in NDEs (Cahal, 1957).
This is from Susan Blackmore's site, taken from The Skeptic Encyclopedia of Pseudoscience (I gather it's her article)
Occasionally, NDEs change from pleasant to hellish, as occurred in one seventy-two-year old cancer patient who was administered naloxone. His pleasant NDE turned to horror and despair as the friendly creatures morphed into the doctors treating him—suggesting that the naloxone (a morphine antagonist) had blocked the endorphins that were providing the pleasant feelings (Judson and Wiltshaw 1983). This is circumstantial, though, and Melvyn Morse has argued that endorphins are not responsible, suggesting that the neurotransmitter serotonin plays a more important role. Of eleven children who had survived critical illnesses, including coma and cardiac arrest, seven reported NDEs, while twenty-nine age-matched controls, who had had similar treatments including the use of narcotics, did not report any NDEs (Morse et al. 1986).
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From the podcast:
Dr. Steven Novella: And in fact, it’s been reported that in patients who have had naloxone, which blocks those receptors, that they have the more negative NDE experience. Why would a drug change the way someone experiences their near-death experience unless it were a brain phenomenon?
Alex Tsakiris: Great. I’d love to look at that study, too. Please send me that reference.
Dr. Steven Novella: I will send you a good overview that gives all of these references that I’m going to be talking about tonight.
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It sounds possibly like Steven Novella is referring to this case reported by Judson and Wiltshaw in 1983, but making more of it than what it is.