Much more very important knowledge about near death experiences

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See the results of world's largest Near death experiences. This study has published recently,
In some cases of cardiac arrest, memories of visual awareness compatible with so called out-of-body experiences may correspond with actual events.
Further studies are also needed to explore whether awareness, explicit or implicit, may lead to long term adverse psychological outcomes including post-traumatic stress disorder.

The recalled experience surrounding death merits a genuine investigation without prejudice.

Future studies should focus on cardiac arrest, which is biologically synonymous with death, rather than ill-defined medical states sometimes referred to as ‘near-death’, 

says Dr Sam Parnia.
According to Parmia in some cases of cardiac arrest, memories of visual awareness compatible with so called out-of-body experiences may correspond with actual events.
A higher proportion of people may have vivid death experiences, but do not recall them due to the effects of brain injury or sedative drugs on memory circuits.