When a doctor hears his patient say he thinks his brain is dead, he knows something is seriously wrong.

That’s what happened when 48-year-old Graham went to see his general practitioner to prove his brain was "dead," according to a 2013 case study in the journal CORTEX.

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According to the case study, Graham knew he had the ability to think, recall and interact with people. But the man somehow also thought that his brain was no longer alive, even while his body was.

Graham’s condition came after his severe depression led to an attempted suicide by electrocution, reports the case study.

Graham was then diagnosed with a rare psychiatric condition called Cotard’s syndrome. The condition involves a person denying the existence of his own body or body parts, according to a different case report in the Journal of Neurosciences in Rural Practice.

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In the rare Cotard’s syndrome cases that have occurred, many patients go through severe malnutrition and starvation. This reaction may happen because patients don’t see the point of eating, sleeping or doing everyday activities if they’re no longer living. In addition, Graham felt compelled to stay at a nearby cemetery, reports The Telegraph.

The severely depressed man said that it “was the closest I could get to death,” and Graham would stay at the cemetery so long that police would have to come to escort him home.

When Graham did finally get medical help, doctors were able to peek at what happens inside the brain of a Cotard’s syndrome patient: A PET scan showed abnormally low metabolic activity compared to a normal person’s brain, reports New Scientist.

One of Graham’s doctors told the magazine that he’d never seen a man walking and talking with Graham’s low level of brain activity. The doctor said it was more similar to someone sleeping or under anesthesia, rather than a person completely awake.

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The images may explain why people with Cotard’s syndrome feel they’re not alive anymore. The brain is essentially asleep even while the body performs activities and moves around. Graham’s metabolic brain activity was rated over 20 percent lower than other healthy individuals, according to the CORTEX case study. Tests also revealed major depression and some anxiety.

The authors of the CORTEX study reached the conclusion that such a major disruption of a person’s thoughts stems from a major disruption inside the brain, affecting a person’s “core consciousness” of himself and events around him.

According to New Scientist, however, Graham has been able to return to a fairly normal life after much psychiatric treatment and medication.