At a point in time when a person is close to death, a set of vivid psychological experiences can occur. These so-called near-death experiences have been reported for centuries.
The classic near-death experience (NDE) includes bright lights, an overwhelming feeling of peace, out-of-body experiences (OBEs), life review, reduced fear of death, and the perception of being in a long tunnel. NDEs are surprisingly common, affecting an estimated 4 percent of the population, as well as up to 18 percent of cardiac arrest survivors.
Historically, they have been linked to the afterlife and used as evidence of the soul, but, just like any other often-reported phenomenon, scientists are keen to get to the biological bottom of it. Perhaps unsurprisingly, there has not been a wealth of research investigating NDEs; the point in time at which they occur make them difficult to pin down in the laboratory.
Recently, Charlotte Martial, from the University of Liège and University Hospital of Liège, both in Belgium, and team set out to get a deeper understanding of the NDE experience. They wanted to discover whether or not people experienced the phenomenon in a similar order. Are NDEs the same for everyone?
This marks the first time that the order of NDEs has been investigated in a scientific manner, according to Martial. She says, "To the best of our knowledge, no study has formally and rigorously investigated whether NDE features follow a fixed order or distribution."
Martial explains that the aim of their study "was to investigate the frequency distribution of these features, both globally and according to the position of features in narratives, as well as the most frequently reported temporality sequences of the different near-death experience features."
Their findings were recently published in the journal Frontiers in Human Neuroscience.
What do NDEs consist of?
To get an accurate picture of the events that take place in an NDE, the researchers analyzed 154 written accounts of the phenomenon. They collated the types of events, how often they occurred, and in which order.
After analysis, the team found that each NDE involved an average of four different phenomena, the most frequent features of which were:
- a feeling of peacefulness (experienced by 80 percent of participants)
- witnessing bright lights (experienced by 69 percent of participants)
- encountering people or spirits (experienced by 64 percent of participants)
Meanwhile, the least common experiences were experiencing speeding thoughts (felt by 5 percent of participants), and having precognitive visions, or seeing events in the future (felt by 4 percent of participants).
As far as the order of events is concerned, 35 percent of people experienced an OBE first; the event most commonly experienced last was the feeling of returning to one's body (felt by 36 percent of participants).
"This suggests that near-death experiences seem to be regularly triggered by a sense of detachment from the physical body and end when returning to one's body."
According to the analysis, the most common order of NDE events - occurring in 22 percent of participants - was as follows:
- experiencing a tunnel
- seeing bright lights
- a feeling of peace
Overall, however, there was no universal sequence of events; the sequence above occurred in fewer than 1 out of 4 experiences. So, although there are commonalities, each NDE is unique.
As Martial explains, "Our findings suggest that near-death-experiences may not feature all elements, and elements do not seem to appear in a fixed order."
"While near-death experiences may have a universal character so that they may exhibit enough common features to belong to the same phenomenon, we nevertheless observed a temporal variability within the distribution of reported features."
The future of NDE research
With a phenomenon as little studied as NDEs, there are still many questions unanswered. In the future, Martial hopes to explore the influence of expectations and cultural backgrounds on an individual's NDE experience. Also, she would like to slowly unpick the "neurophysiological mechanisms" behind NDEs.
As neuroscience forges ahead, various organic theories of NDEs have been put forward, including:
- random eye movement (REM) sleep intrusion, in which some characteristics of REM sleep occur during wakefulness
- pharmacological factors, perhaps involving N-methyl-D-aspartate receptors
- altered blood gas levels, such as elevated levels of carbon dioxide
- activity in the temporal lobe, an area of the brain thought to be involved in religious and mystical experiences
However, testing any one theory in such a difficult-to-pin-down experience is a true challenge. New discoveries in this field of research are likely to be few and far between, but every new insight gained is guaranteed to be fascinating.