Most of us are well aware of Justin Bieber's fall from grace a few years back.

The Canadian pop star went from being a teen heartthrob to a cliched Bad Boy, being arrested for drag racing in 2014 in Miami and generally going off the rails.

It seems that the 'Baby' singer is infinitely more settled these days, but now he's discussed an element of his risky behaviour.

The latest episode of his new YouTube web series 'Seasons' sees him open up about his drug use.

He reveals that he first started smoking marijuana at the age of 12 or 13 and progressed to 'popping pills' and 'sipping lean' (a mixture of cough medicine and fizzy drinks).

"It was just an escape for me," he said. "I was young, like everybody in the industry, or in the world, who experiment. But my experience was in front of cameras and I had a different level of exposure. I had a lot of money and a lot of things, so then you have all these people around me hanging on and wanting stuff from me, knowing I was living this lifestyle that they also wanted to live."

He said that people weren't aware of how bad his addiction became.

"I decided to stop because... I was like, dying," he said. "My security were coming into the room at night to check my pulse. People don't know how serious it got. It was legit crazy-scary."

Bieber releases his new album 'Changes' on February 14th.