According to a source, the pop star had relapsed for "a few months" before her overdose.
"The disease Demi has is a vicious liar and it's been telling her for some time that she can use just a little, just one or two drinks, nothing too serious, nothing bad will happen, she can keep it under control," the source told PEOPLE. "And when she could, for a few months, it seemed like vindication to her, proof that she could keep it under control."
The source continued, "It led to her believing in the myth of moderation and controlled consumption, which absolutely does not work if you are an addict."
The insider added that Lovato's recent move away from life coach Mike Bayer led some close to her to believe that Lovato felt she could use responsibly.
"This is absolutely what so many people feared would happen. She has not been sober for quite some time but more tragically, has had no interest in being sober."
A second source said that "things have been a mess for months."
"She and her team severed ties, and they played a large part in getting her sober years ago," the insider claimed. "She hasn't been in a good place."
"Start using again and it's a slippery slope right back to rock bottom," the source added. "The minute she started using again, the clock was ticking down to this exact moment."
Lovato reportedly overdosed at her Hollywood Hills, California home and is not under any form of criminal investigation, PEOPLE reports. Officers did not find any drugs at the scene and the 25-year-old reportedly would not answer when asked what she had taken.
TMZ reports that the singer was found unconscious and was revived at the scene with Narcan, an emergency treatment for narcotic overdoses. The outlet initially reported that Lovato had overdosed on heroin, but sources told PEOPLE that was not the case.
The singer's spokesperson confirmed that she was awake on Tuesday evening.
"Demi is awake and with her family who want to express thanks to everyone for the love, prayers and support. Some of the information being reported is incorrect and they respectfully ask for privacy," they said in a statement.
Photo Credit: Getty / Timothy Hiatt