A patient has written a disturbing account of life with a condition which makes him think he is dead - and how he spent his days in graveyards as it was "the closest I could get to death".
The British man, identified only as Graham, woke up nine years ago utterly convinced that he was no longer alive even though he was still breathing.
Doctors diagnosed him with Cotard's Syndrome, which is also known as Walking Corpse Syndrome because it makes people think they have turned into zombies.
Graham did not believe them, however, and insisted that his brain was dead.
The unusual condition emerged after Graham, who suffered from severe depression, tried to commit suicide by taking an electrical appliance with him into the bath.
Eight months later he told doctors that his brain had died or was, at best, missing.
He lost interest in smoking, stopped speaking and refused to eat as there was "no point because I was dead".
Only through months of therapy and treatment was he able to overcome the condition and live anything approaching a normal life.
Cotard's Syndrome is among the most rare diseases in the world and it is thought that it affects just a few hundred people at any one time.
It is linked to depression and comes in a variety of forms including some who feel that their limbs are no longer functioning.
Writing in New Scientist magazine, Graham describes how baffled doctors referred him to neurologists Adam Zeman at the University of Exeter and Steven Laureys at the University of Liege in Belgium.
"I didn't feel pleasure in anything. I used to idolise my car, but I didn't go near it. All the things I was interested in went away," he said.
"I lost my sense of smell and my sense of taste. There was no point in eating because I was dead."
The nadir was when he felt compelled to go to his local cemetery as he thought he would fit in.
"I just felt I might as well stay there. It was the closest I could get to death. The police would come and get me, though, and take me back home."
Graham's recovery started with scans which found levels of activity in parts of his brain that were so low they were more consistent with somebody in a vegetative state.
Laureys said: "'I've been analysing [brain] scans for 15 years and I've never seen anyone who was on his feet, who was interacting with people, with such an abnormal scan result. Graham's brain function resembles that of someone during anaesthesia or sleep."
After his own regime of therapy and drugs, Graham is on the road to recovery. He said that he is not really back to normal but can go out of the house on his own and "feels a lot better" than he was.
"I don't feel that brain-dead any more. Things just feel a bit bizarre sometimes.
"I'm not afraid of death. But that's not to do with what happened - we're all going to die some time. I'm just lucky to be alive now."