For The One Show, Anita Rani has been investigating near death experiences.
Twenty five British hospitals have agreed to take part in an international study of the subject. Click here for more information.
Hundreds of survivors have reported near death experience stories, but the evidence, say the experts, is purely anecdotal.
Psychologist Dr Susan Blackmore believes that there are many medical explanations to why people have near death experiences - that they are simply the processes of the body and mind under stress, creating hallucinations.
Have you ever had a near death experience? Are they fact or fantasy?Please leave your first name and location on your blog comment, if you'd like it to be mentioned on The One Show programme.