Justin Bieber Opens Up About Lyme Disease and Health Struggles in Docuseries

Justin Bieber went to a dark place as he grew dependent on drugs and dealt with various health issues, but he's committed to getting better and brightening up his days ahead ... he says so himself.

Justin opened up about his long run of health struggles -- both physically and mentally -- on the latest episode of his YouTube 'Seasons' docuseries titled, "The Dark Season." He says it culminated in a series of tests last year that finally revealed the problem -- Lyme disease.

Bieber, who's undergoing a round of NAD IV therapy in the video, explains how the diagnosis helped him finally make sense of why he was feeling so terrible ... and what he can do to handle it going forward.

A couple of Justin's doctors, along with his wife, Hailey, also talk about how the discovery of his Lyme disease and chronic mono has been life-changing ... for the better.

Bieber's now laser-focused on improving his health, and not just for himself. He says ... "Being the best me is gonna help me be the best husband, the best father, the best friend that I can possibly be. And, for all the fans that want to enjoy the music that I make. I can't do it if I'm not healthy."