Nick Jonas has confessed he was "genuinely concerned" close friend Demi Lovato's addiction to drugs would end her life.The 23-year-old pop stars have known each other since their early teens, and Nick watched thesinger struggle with substance abuse, self-harming, and eating disorder problems, which prompted her to seek rehab help in 2010, at the age of 18.She recently celebrated her four-year sober anniversary, and while Nick is extremely proud of his pal now, he admits he used to fear receiving news about Demi's demise."It's been years of working on herself and getting better," Nick explains in a new interview with Entertainment Weekly.Are you surprised that these two kids from are doing this huge tour together now?It's surprising just in the world we live in -- it's tough to stay friends with people who are in the industry over this much time. They've seen each other go through so much, personally and in their careers.* Demi Lovato says her choice to go nude and make-up free for magazine was liberating "But I was genuinely concerned that I might lose my friend."Nick, who is heading out on a joint North American tour with Demi this summer, also gushes about his ex-girlfriend Miley Cyrus, who he dated years ago when both were breakout stars on the Disney Channel. "I still think it's one of the best pop songs of the last 10 years.And you know, she's always been so outspoken and authentic to who she is, so it was only a matter of time before she really owned that, and I'm proud of her."And the singer admits that while he doesn't keep in contact with Miley, he continues to heap praise on her from afar, adding, "I don't have a relationship with her now really, but that's not because we have any bad blood - we just sort of run in different circles."It's a lot like watching your high school crush do well, just on a bigger scale."Nick and Miley dated on-and-off from 2006 to 2008.
“You’d think they’re siblings, sometimes more than Nick and I. Demi’s a great listener, and she keeps Nick smiling — she’ll always make a serious situation laughable. It’s difficult to take a backseat and say, ‘Let’s work together and figure out something great.’ I commend them both for that,” Joe, 26, told .It's cool to see this bond now that they're adults. You'd think they're siblings, sometimes more than Nick and I. Demi's a great listener, and she keeps Nick smiling -- she'll always make a serious situation laughable. It's difficult to take a backseat and say, "Let's work together and figure out something great." I commend them both for that.I think it's nice for an audience as well -- they get to watch Nick and Demi grow up, not only together, but also musically. So, they've found great support with one another and they lean on each other creatively. Demi Lovato & Nick Jonas: A Timeline of Their Friendship Demi talks about writing "Gonna Get Caught" when you two were dating."She's amazing - and a better singer, too, because she's healthy.READ MORE: * Lorde leaves Lady Gaga's party with Nick Jonas * Demi Lovato supports Kesha, takes aim at Taylor Swift?