'I was, like, dying. People don’t know how serious it got It was legit, crazy scary.'

After an episode dedicated to his love story with wife Hailey Bieber, Justin Bieber goes down a dark path on the fifth part of his Seasons YouTube series, opening up for the first time about the devastating drug issues he suffered through is teens and early 20s before getting sober.

"The Dark Season" opens with Bieber returning to the spot behind his childhood apartment building in Stratford, Ontario, where he first smoked pot as a 13-year-old. "I got super stoned, then I realized I liked weed a lot," he says, quickly understanding at that young age that it could be a problem that might lead to a dependency.

"There was a time when I was sipping lean, I was popping pills, I was doing Molly, shrooms, everything," Bieber says of his attempt to escape from his problems as a younger person in the music business. "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." Unlike most teenagers, though, he was doing his growing up in the public eye and had a lot of people around him who wanted to do those things and live his baller lifestyle vicariously.

Wife Hailey hints at Justin's undiagnosed "horrible, crazy, crippling anxiety," which both speculate might have led to the self-medication. Longtime manager Scooter Braun calls the years from 19-21 a "really dark period," during which other members of Bieber's circle say they also stepped away as the singer made a series of bad decisions that included drag racing, DUI, assault, excessive partying and generally boorish behavior. "He's gone through a lot in a very short life," says Braun. "You don't always agree with someone's decisions in that moment. They're young people making very big decisions that affect a lot of people. And sometimes in those scenarios you're going to make the right decisions. Sometimes you're gonna make wrong."

Flashing to a series of tabloid headlines and videos of his various misadventures, Bieber labels himself a basically good kid, but also a "s--thead" class clown who did poorly in school and didn't respect authority and who never really had good role models.

"People don't know how serious it got," says Bieber, describing a time when he would wake up in the morning and pop pills and smoke a blunt to start his day. "I started valuing the wrong things in this business because there were things dangling in front of me. 'If I get this I'll be happy. If I do this I'll be happy'... The truth is, I never had the tools. My parents never gave me those tools to be a good team player."

Hailey Bieber says she wasn't really back in Justin's life until he got sober. By that point, Justin says, things had gotten very, very dark. "I decided to stop because I felt like I was, like, dying. People don't know how serious it got," he says, describing his security detail coming in at night to check his pulse. "It was legit crazy scary."

The episode also includes an interview with the brain disorder specialist, Dr. Daniel Amen, who helped Bieber adjust to his sober life, describing the singer's sleepless, anxious struggles as he was trying to get off drugs, as well as footage of the hyperbaric oxygen chamber that he and Hailey say has helped him deliver more oxygen to his brain to push down stress levels. It also shows Bieber getting some medical attention to deal with his previously undisclosed Lyme disease diagnosis, as well as the Epstein-Barr virus, a type of mono that can cause exteme fatigue and fevers.

"He just felt so sick and there was no explanation for what was going on," says Hailey after Amen reveals that Bieber was misdiagnosed with bipolar disorder and put on Lithium by a psychiatrist who didn't look at the singer's brain to diagnose what turned out to be two major, chronic ailments. With his second chance, Bieber, 25, realizes the errors of his youthful ways.

"There are so many people that have gifts and an opportunity to make a change and they end up either losing it or using their gifts for selfish reasons," he says. "I see so many talented people.. it almost feels like they're wasting something so precious. It's up to us as individuals to use the gift that we've been given, whatever it may be, to contribute."

Watch the episode here.