A teenage girl believed she was dead for three years because of a condition known as Walking Corpse Syndrome.
The condition – officially called Cotard's syndrome – is a rare form of delusional psychosis that made Haley Smith, 17, believe she no longer existed.
Some people with Cotard's have even died from starvation as they think they no longer have to eat to stay alive.
But Haley is now recovering, thanks to a mix of therapy and Disney films, which she says brought her back to life.
Haley, from Alabama, U.S., said the strange feelings began after her parents divorced when she was 14.
She told the Mail: "One day when I was sitting in an English class I had this really weird sensation that I was dead and I couldn't shake it."
Later, as she walked home, she recalled: "I thought about visiting a graveyard, just to be close to others who were also dead."
The feelings returned a few days later, and she couldn't shake it.
She said: "I'd fantasise about having picnics in graveyards and I'd spend a lot of time watching horror films because seeing the zombies made me feel relaxed, like I was with family."
As time went by, Haley decided to embrace her 'new' life.
She said: "I decided to eat whatever I wanted because I couldn't put on weight if I was dead."
She even stopped talking to her friends, who had begun to grow concerned about her behaviour.
Eventually, she confided in one.
She said: "I thought he'd think I was a freak but he just nodded and listened. It gave me the confidence to tell my dad."
Her father, Floyd, urged her to see a psychiatrist, but it was two years until Haley finally plucked up the courage and she was diagnosed with Cotard's syndrome.
Haley explained: "It's a rare condition where sufferers believe they or parts of their body no longer exist. It was so amazing to find out it was a real illness."
And research showed that, however rare the condition may be, she was far from alone.
Cases of Cotard's Syndrome date back to 1788 but it was formally identified by French neurologist Jules Cotard in 1880.
Among the handful of cases over the years was a 53-year-old woman in New York who in 2008 claimed that she stank like rotting fish because she was dead.
She said: "I went online and found stories of other people who suffered from it. They wanted to spend time in graveyards too. It made me feel so much better that I wasn't the only one."
After several sessions with her therapist, Haley started to recover – with a little helping hand from Disney.
She said: "Watching Disney films gave me a warm, fuzzy feeling. The Little Mermaid, Aladdin, Sleeping Beauty, Bambi – I watched them all.
"I asked my boyfriend Jeremy: 'How can I be dead when Disney makes me feel this good?'."
Gradually, through the magic of the movies, Haley came back to life.
She said: "Jeremy helped me so much – as did Disney – and we're hoping to get married soon and then
get jobs in Disney World.
"Being a corpse was the most bizarre experience, but I'm so glad I managed to get out alive."