According to at least one person I've spoken with recently, the fact that people have near death experiences is supposed to convince me that there is an afterlife. At first glance, it does seem kind of convincing. Johnny gets into a car crash and sees God. Jane almost drowns in a swimming pool and has an "out of body experience". Supposedly, the soul leaves the body and is in some sort of temporary limbo. They're not really alive. They're not really dead. It sounds kind of groovy, but I'm not buying it.

 I'm not buying it for two reasons. First, no hard and fast evidence has ever surfaced that supports the notion of either a) an afterlife, or b) a metaphysical plane (both of which would, presumably, be required for a "near death experience&quot. Second, there are plausible explanations for NDEs that don't require us to abandon a materialistic view of the universe (which, by the way, there is pretty good evidence for) such as lack of oxygen to the brain which could induce sensations and experiences similiar to NDEs.

Being a skeptic, I tend to like peer-reviewed journals. They weed out most of the woo-woos and pseudoscience and give you things like operational claims and statistical analysis. With that said, I came across a study in the journal Neurology earlier this year, penned by Nelson et al. entitled Does the arousal system contribute to near death experience?¹ that gives us another plausible explanation for NDEs - which is where sleep comes into the picture.

Narcolepsy is a disorder of sleep whose signs and symptoms are excessive daytime sleepiness, cataplexy (loss of muscle tone during periods of intense emotion), hypnagogic hallucinations (seeing or hearing things that are not there as one goes to sleep), decreased rapid eye movement sleep latency (REM - the stage of sleep when we dream), and sleep paralysis (having the sensation of being awake, but not being able to move). Of particular importance, with respect to this issue, are the last two: hypnagogic hallucinations and sleep paralysis.

Now, back to the study. What the authors did was they contacted people who had NDEs at some period in their life as a result of events ranging from motor vehicle accidents to drug overdoses. In the end, they were able to interview and include 55 participants in the study. They gender and age matched those 55 with another 55 participants to form a control group. They conducted structured interviews with both groups. Some of the interesting results are below. "NDEs" refer to individuals who have experienced near death experiences and "Control" refer to individuals in the control group. The percentages following each indicate how many individuals in each group answered affirmative to the question asked. "p" refers to the liklihood that those results were arrived at due to random error (chance). Here we go:

Question #1
"Just before falling asleep or just after awakening, have you ever seen things, objects, or people that others cannot see?" (Referring to hypnagogic / hypnopompic hallucinations)

NDEs: 42%
Control: 7%
p < 0.0001

Question #2
"Just before falling asleep or just after awakening, have you ever heard sounds, music, or voices that other people cannot hear?" (Referring to auditory h/h hallucinations)

NDEs: 20%
Control: 4%
p < 0.0001

Question #3
"Have you ever awakened and felt you were unable to move or felt paralyzed?" (Referring to sleep paralysis

NDEs: 46%
Control: 13%
p < 0.0001

Question #4
"Have you ever had sudden muscle weakness in your legs or knee buckling?" (Referring to cataplexy)

NDEs: 7%
Control: 0%
p = 0.12

Fairly interesting, if I do say so myself. It's hypothesized that, essentially, people in life threatening situations who experience NDEs are not having an "out of body experience" and are not going to some metaphysical realm. They are dreaming. If CNS arousal reaches a sufficient level (I would assume seeing a Mack truck bearing down on you at 65mph would suffice) and the sympathetic nervous system is triggered, it can can cause the arousal system responsible for REM sleep (which is when we dream) to kick on. Similiar REM intrusion is also thought to be an explanation for alien abduction stories (ever notice how they almost unfailingly occur at night, in someone's bedroom?).

It probably goes without saying that the sample was fairly small (n=55), and this doesn't prove that malfunctions of the arousal systems for sleep and REM are responsible for NDEs in every case, but it does suggest that they are involved. 

Sources 

¹Nelson, K., Mattingly, M., Lee, S. & Schmitt, F. 2006. Does the arousal system contribute to near death experience? Neurology 66(1), pp 1003-1009.

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