You’ve seen them dance to Michael Jackson’s Thriller and read about their brain-eating adventures in the days of Jane Austen. There are zombie walks, zombie pub crawls and zombie flash mobs. Come Sunday, you’ll even be able to watch zombies in their own AMC TV series.

Yes, the walking dead are everywhere these days -- even in the mental disorders bible the DSM -- thanks to a rare neuropsychiatric disorder known as Cotard delusion, or walking corpse syndrome.

First described by French neurologist Jules Cotard in 1882, the delusion is linked to depression and brain injury in some cases, and thought to be neurologically related to Capgras delusion. In Capgras, a disconnect in the region of the brain that recognizes faces causes people to believe their loved ones are imposters. In Cotard’s, that disconnect results in them not recognizing their own face; as a result, they come to believe they’re dead.

But people with Cotard delusion don’t just think they’re dead. In advanced cases, they sometimes believe their flesh is beginning to rot or that some of their internal organs or their blood is missing.

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In a case written about in the journal “Psychiatry” in 2008, a 53-year-old Filipino woman with Cotard delusion was admitted to a psychiatric unit after she told her family she was dead, smelled of rotting flesh and wanted to be taken to a morgue so she could be with other dead people.

Another case reported in 2008 involved a 28-year-old pregnant housewife from in Kashmir, India, who became increasingly depressed and eventually began telling people that her liver was “putrefying,” her stomach was missing and that her heart was “altogether absent.”

In another case from 2001, a 44-year-old man fell into a deep depression after he was unable to find work. Homeless, unemployed and unable to obtain psychiatric treatment, his symptoms worsened over a six-week period until he began to tell people that he had “melted away” and was “dead.” In the ensuing weeks, according to a letter in the journal Psychiatric Services, “his symptoms and daily functioning worsened. He continued to voice delusional beliefs, such as ‘my brain’s rotted away,’ ‘parts of my insides are gone’ and ‘I’m dead.’”

All three patients received treatment – and relief – through drugs and/or ECT (electroconvulsive therapy) and eventually came to realize they were not actually walking corpses.

But other individuals have not been as fortunate, particularly those who’ve fallen victim to a voodoo zombie curse. Practiced primarily in Haiti during the 18^th and 19^th centuries, the voodoo zombie ritual first involves slipping the potential victim a substance – usually a neurotoxin derived from the puffer fish -- in order to make it appear as if they’re dead. They’re then buried (sans embalming), and a day or two later, dug up and revived.

“But not to the point that they know who they are,” says Brad Steiger, author of “Real Zombies, the Living Dead and the Creatures of the Apocalypse.” “They’re in a perpetual trance, a twilight state. They’re brought back to serve as a slave for a voodoo priest or priestess.”

Steiger, who’s written about the paranormal for the last 50 years, says there have been many cases of "real-life zombies" over the years, many involving people who would spot a supposedly deceased relative working away in the sugar cane fields. He retells this spooky legend, which is included in his book: “There was a gentleman from Florida who went to Haiti and was dancing with a lovely young Haitian girl when he suddenly felt a prick on his arm,” he says. “He didn’t pay any attention to it, but the next thing he knew, he woke up with a hoe in his hand. He still had his suit and tie on but was working in the Haitian fields. Luckily, he was able to recover enough to eventually make it back to Florida.”

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