"Doctors struggled to figure out what was wrong with him, but couldn't put their finger on it until late last year," the source claims, adding he battled with the undiagnosed condition for much of 2019.
The insider also says he will make it clear in his new documentary that his battle with the illness was actually brought on his depression.
Lyme disease is a bacterial infection that's typically contracted through a tick bite. It includes symptoms such as fevers, headaches, skin rashes and fatigue. While the disease is uncommon, stars like Bella Hadid, Gigi Hadid, Shania Twain, Alec Baldwin and Ben Stiller suffer from it.
Since being properly diagnosed, a relieved Justin star now takes medication to combat the disease which has also cleared up his skin and his mood.
While the news may come as a shock to some, the "Where Are U Now" singer sparked concerns for his health on multiple occasions after he was spotted leaving the Beverly Hills medical centre with an IV in his arm. He was also seen crying uncontrollably in his car, while also looking miserable during several dates with his then-girlfriend, Hailey.
It's now understood he was given a series of medications to combat the ailment before he was officially diagnosed. The medication he was prescribed also affected the state of his skin, which was a major point of anxiety for the star.
In September 2019, Justin opened up about his mental health woes, telling his Instagram followers that he had been "struggling a lot" and was "feeling super disconnected and weird". He also detailed his struggles with substance abuse which he says was brought on by his inability to deal with such a high level of fame at such a young age.
“I started doing pretty heavy drugs at 19 and abused all my relationships. I became resentful, disrespectful to women, and angry. I became distant to everyone who loved me, and I was hiding behind a shell of a person that I had become," he revealed. "
"I went from a 13-year-old boy from a small town to being praised left and right by the world, with millions saying how much they loved me and how great I was. You hear these things enough as a young boy and you actually start believing it."