Rising out of your body, traveling through a dark tunnel, heading towards a brilliant, bright light… these are all commonly-cited characteristics of what’s typically termed a near-death experience, or NDE. But beyond these classic tropes, are there any actual symptoms of near-death experiences? According to a new study, there might be — and what’s more, the biggest symptom of all might have to do with your sleep cycle. The research was recently presented at the 5th European Academy Of Neurology Congress, and although it hasn’t yet been published in a peer-reviewed journal, the study is available to read online for free through the open-access pre-print repository bioRxiv.
While there’s still an awful lot we don’t know about near-death experiences, we do know that they “share phenotypical features with those made during rapid eye movement (REM) sleep,” as the researchers put it — that is, the part of your sleep cycle when you’re most likely to have particularly vivid dreams. REM sleep intrusion in particular — that is, an interval of REM sleep that appears out of its usual spot in the NREM-REM sleep cycle — was of interest to the researchers; what’s termed “REM sleep intrusion into wakefulness” is what’s responsible for phenomena like sleep paralysis.
So, that’s what the researchers set out to explore: They wanted to see if they could “estimate the frequency of near-death experiences and REM sleep intrusions reported in a large sample of adult humans” and see whether there was a correlation between the frequency of REM sleep intrusions a person has and whether they tend to report having experienced a near-death experience.
Participants included 1,034 people from 35 countries — mostly within Europe and North America — 289 of whom claimed to have had a near-death experience. All participants were recruited through an online crowdsourcing platform and completed a questionnaire covering their demographic, REM sleep intrusion, and whether or not they had ever experienced a near-death experience; if they reported never having experienced an NDE, the questionnaire finished there, while if they reported that they had, they went on to take the 16-item Greyson Near-Death Experience Scale. They were also given the opportunity to describe their experience in detail. Of the 289 people who claimed to have had a near-death experience, 106 of them scored seven or more points on the Greyson NDE Scale, thereby making the total number of confirmed near-death experiences 106 out of 1,034 participants — or, about 10%.
Among those who claimed to have experienced an NDE, the most commonly reported symptom was “abnormal time perception” — that is, the participant reported feeling or sensing time moving either faster or slower than how they usually experienced it. A whopping 87% of respondents reported experiencing this particular symptom. Other commonly noted symptoms included “exceptional speed of thoughts,” which 65 percent of those who claimed to have had an NDE said they experienced; “exceptional vivid senses,” reported by 63% of NDE-havers; and “feeling separated from one’s body” (think out-of-body experiences), which 52 percent of NDE-havers claimed to have experienced.
The language the participants used to describe these symptoms was often thematically similar. For example, one participant described seeing their “life… flashing before me in my head,” while another said they experienced “a sense of not having done all the things I was meant to do.” Concerning the feeling of being separated from your body, three different accounts noted experiencing “a truly out-of-body experience where my eyesight and visual became incredibly abstract,” an awareness “of being outside my body,” and the feeling that “I could not control my body.”’
But the most notable finding had to do with the question it originally set out to explore: The relationship between NDEs and REM sleep intrusion. Nearly half of people who scored seven or higher on the Greyson NDE Scale exhibited evidence of REM sleep intrusion — and even after the researchers adjusted for factors like age, gender, place of origin, employment status, and perceived danger of the situation that the NDE arose from in the first place, they determined that “people with REM sleep intrusion were more likely to exhibit near-death experiences than those without REM sleep abnormalities.” Indeed, REM sleep intrusion was determined to be “the only factor that remained significantly correlated with near-death experiences.”
Now, it’s worth noting that the researchers aren’t saying that their work proves that near-death experiences are nothing more than vivid dreams; the jury’s still out on whether NDEs are really a thing or not. But the study does show that the mechanisms responsible for REM sleep intrusion into wakefulness and for NDEs are related — and that’s a pretty big finding. Said lead researcher Dr. Daniel Kondziella of the University of Copenhagen in a press release, “Our central finding is that we confirmed the association of near-death experiences with REM sleep intrusion. Although association is not causality, identifying the physiological mechanisms behind REM sleep intrusion into wakefulness might advance our understanding of near-death experiences.”
As NBC notes, the paper hasn’t yet been published in a peer-reviewed journal. That doesn’t necessarily mean it’s not credible; however, peer review does lend a certain legitimacy to studies, making it an important part of the research process. (Although it’s also worth noting that the peer review process also isn’t infallible; in fact, it’s been found to be susceptible to bias in and of itself in a wide range of cases. ) What’s more, the paper itself acknowledges that online studies have certain limitations, as well. For one thing, wrote the researchers, “complex clinical and ethical notions are impossible to fully implement in survey form”; for another, although a number of demographic factors were taken into account in this study, there still remain “many with potential importance such as religiosity that [the researchers] did not assess.”
Still, though — the findings of this paper are fascinating and worth further study. What’s more, the current study did manage to replicate the findings of an earlier study while correcting some of that study’s issues. (The criticism of the earlier study had to do with selectional bias; according to Dr. Kondziella, recruiting participants through a crowdsourcing platform eliminated this problem.) The study itself can be read in full here.