Jack Osbourne got carried away with drugs and alcohol, he told People in his first interview since checking into rehab April 23.
"I got caught up in my new lifestyle," he said on his fourth day of treatment. "Once I realized this, I voluntarily checked myself into a detox facility for my own health and well-being."
Jack took a break from partying in January after admitting to his mother he was overindulging in marijuana and alcohol, according to the magazine, but he relapsed later while spending time in his parents' Malibu home.
The 17-year-old's admission to Las Encinas Hospital in Pasadena, California, has not been captured by cameras, as the third season of "The Osbournes" wrapped shooting in February.
People also published the first comment from Jack's famous father in the weekly's latest issue. "It takes a lot of courage and strength to admit you need help, and both Sharon and I are proud Jack is facing his problems head-on," Ozzy said.
The latest Us includes an interview with Kelly, who said the family didn't know how serious Jack's problem was because they hadn't been together for a while.
"I was on tour, Mum was working on her TV show, and Dad's in rehearsal [for Ozzfest]," Kelly said, adding that Jack's now "in really good spirits."
None of Jack's family has speculated on how long he will stay at the facility, which specializes in drug addiction and psychiatric care. A spokesperson for Jack has not returned calls.
Ten new episodes of "The Osbournes" will begin airing June 10.