Near-death experiences are not paranormal but triggered by a change in normal brain function, according to researchers.
Psychologists who reviewed a range of phenomena such as out-of-body experiences, visions of tunnels of light or encounters with dead relatives, say they are tricks of the mind rather than a glimpse of the afterlife.
Researchers at the Universities of Edinburgh and Cambridge say that most of the experiences can be explained by a reaction in the brain prompted by a traumatic and sometimes harmless event.
The researchers say that many common near-death experiences could be caused by the brains attempt to make sense of unusual sensations and perceptions occurring during a traumatic event.
Out-of-body experiences, for example, may happen when there is a breakdown in the brains multi-sensory processes, and visions of tunnels and bright lights could stem from a breakdown in the brains visual system caused by oxygen deprivation.
The new study also points to the effects of noradrenaline, a hormone released by the mid-brain which, when triggered, may evoke positive emotions, hallucinations and other features of the near-death experience.
Approximately three per cent of the US population say they have had a near-death experience, according to a Gallup poll. Near-death experiences are reported across cultures and can be found in literature dating back to ancient Greece.
"Some of the studies we examined show that many of the people experiencing a near-death experience were not actually in danger of dying, although most thought they were. The scientific evidence suggests that all aspects of the near-death experience have a biological basis," said Caroline Watt, School of Philosophy, Psychology and Language Sciences.
The research is published in the Journal Trends in Cognitive Sciences.