Writing for Seventeen magazine, the actress, who left treatment after three months in January, revealed that she was deeply unhappy for many years before deciding to confront her issues head-on.
"I basically had a nervous breakdown. I was really bad off. My parents and my manager pulled me aside and said, 'You need to get some help'," she recalled. "It was an intervention. I wanted freedom from the inner demons. I wanted to start my life over.
"One of the reasons I was so unhappy for years was because I never embraced my emotions and I was trying to stay in control. In treatment, all of the negative things I did were stripped away and I had to start processing my feelings."
Lovato also confessed that much of her treatment was aimed at dealing with her eating disorder, which she continues to recover from post-rehab.
Her interview with Robin Roberts of 20/20 will air Friday, April 22.