The Dementors in Harry Potter are a metaphor for JK Rowling's own experience with depression.

JK Rowling is possibly the most renowned and successful author in recent history.

She’s penned seven bestselling books in the Harry Potter series and made millions of dollars.

But her life hasn’t always been easy. When the first Harry Potter book was published in 1997, JK Rowling was a single mother, who was living on benefits in Edinburgh.

She felt like a failure and was being treated for clinical depression.

That’s why she wrote the Dementors into the series (their name is a blend of ‘tormentor’ and ‘dement’) to explore her own experience with depression.

This is how Rowling described them in the book, “If it can, the Dementor will feed on you long enough to reduce you to something like itself… soulless and evil.

“You’ll be left with nothing but the worst experiences of your life.”

Rowling wrote that they “freeze your insides” and “they don’t need walls” to keep their prisoners in, because their prisoners become “trapped inside their own heads”.

Rowling, obviously, was eventually able to defeat her own Dementors and she went on to pen the first Harry Potter book.

“I had an old typewriter and a big idea. I had failed on an epic scale. I was jobless, a lone parent and as poor as it is possible to be in Modern Britain without being homeless,” she’s said.

“Rock bottom became the solid foundation on which I rebuilt my life.”

The story goes the idea for the novel that started it all, Harry Potter and the Philosopher’s Stone, came to Rowling during a four-hour delayed train ride while she was working at the Chamber of Commerce in Manchester. She begun writing the stories on her typewriter before moving to Portugal to become an English teacher.

There, she met, fell in love with and married Portugese television journalist Jorge Aranted with whom she had a daughter Jessica, now 24. Four months later, the couple separated and in December 1993, Rowling moved to Edinburgh, Scotland to be near her sister.

It was during this period when Rowling was at her lowest point.

“I stopped pretending to myself that I was anything other than what I was and began to direct all my energy into finishing the only work that mattered to me,” she said in a 2008 address to Harvard University.

“Had I really succeeded at anything else, I might never have found the determination to succeed in the one arena in which I believed I truly belonged.”

After completing the manuscript in 1995, Rowling was initially rejected by 12 publishing houses, before finally being picked up by Bloomsbury – largely due to the chairman’s eight year old daughter, who loved the first chapter she was given to review. Initially 1,000 copies were published in 1997, with 500 given to libraries.

All her novels have since smashed sales records since, with millions of copies sold.

The last four Harry Potter books have consecutively set records as the fastest-selling books in history and have been translated into 65 languages. It’s led to a billion-dollar film franchise, spin off books, merchandise, a play and even theme parks.