The Jonas Brothers' heartthrob came clean in a candid interview with New York Magazine that was released on Sunday (01Dec13), in which he opened up for the first time about his month-long relationship with his Camp Rock co-star.
In the piece he says, "I really got to know her and got to see the ins and outs of what she was struggling with, like drug abuse. I felt like I needed to take care of her, but at the same time I was living a lie, because I wasn't happy but felt like I had to stay in it for her, because she needed help. I couldn't express any of that, of course, because I had a brand to protect."
He continues, "It was an insane situation to be in. Things kept building up, and Demi ended up punching a girl in the face on a plane, because she thought the girl was blaming her for something. Everybody gasped, and the girl just started bleeding.
"That's when her team and her family told her, 'You need to go into rehab.' I remember being in South America, and fans immediately jumped to the conclusion that we kicked her off the 2010 tour, and they just hated on us for it."
Lovato subsequently went to rehab for her drug addiction and depression issues, and has been sober ever since, and on Monday (02Dec13), she took to Twitter.com to show her support for her old pal.
She wrote, "@joejonas love you brother. #family/friendsforever."
Demi has previously stated that while she was immediately enraged after their breakup, they have since mended their relationship and are still friends.
She told U.S. news programme Nightline, "I can fortunately say that him, and his brother Nick (Jonas), have always been there for me and are literally family, and like brothers... we have a great friendship. And we may not be as close as we used to be, but that's Ok."