Chances are the last time you used a colouring book you didn't have a mortgage, a family or even a job.

But a new trend is emerging that has adults picking up their pencil crayons and smelly markers once again.

Adult colouring books are flying off the shelves​ at Mona Lisa Artists' Materials in Calgary and store manager Jennifer Beeger says she sells at least 50 per week. 

"Lots of people want to revert back to their childhood and their happy places, and colouring was one of those things for a lot of people," said Beeger. 

Adult colouring book

Adult colouring books are far more detailed than children's colouring books and each page can take days, sometimes weeks, to fill in. (Danielle Nerman/CBC)

"I think it's partly a meditational or relaxation type of a thing because we're in such an instantaneous society. By taking the time and colouring, it just takes your mind off all of the pressing things that are right at your fingertips, literally."

Adult colouring books come in a variety of themes from animals to paisley designs.

They're also far more detailed than children's colouring books.

"Depends on how much patience you have," said Beeger. "You could spend hours doing one colouring [or] you could work a week on some of them."

While most of her customers colour with pencil crayons, she wouldn't be surprised if some decided to use crayons.

"Some people like the smell of crayons, it makes them think of elementary school," she said.

Scottish illustrator Johanna Basford made headlines recently because her colouring book, Secret Garden, has sold well over a million copies worldwide.

Secret Garden adult colouring book

Johanna Basford found out just how popular adult colouring books can be with the release of Secret Garden. (CBC)