At the age of 25, after a "catastrophic" marriage, J.K. Rowling found herself to be a single mother with little money.

"At that point I was definitely clinically depressed," she once told Oprah in a televised interview.

"It's so difficult to describe [depression] to someone who's never been there, because it's not sadness. I know sadness. Sadness is to cry and to feel. But it's that cold absence of feeling - that really hollowed-out feeling. That's what Dementors are," she said of the cloaked creatures which feed on happiness in the Harry Potter series.

Knowing the feeling all too well, the author offered advice to a fan who asked her how to get rid of her personal Dementor last night.

J.K. Rowling offers touching advice to a fan suffering depression