10/16/2013 at 11:00 AM EDT
Ten years ago, the hit TV series The O.C.
made 17-year-old Mischa Barton an instant "it" girl. Within a few years, however, she was the talk of Hollywood for a different reason as her partying grew out of control.
"We thought, 'Work hard, play hard,' " she says of those years. In 2007, she was arrested for DUI. Then in 2009, shortly after her parents attempted an intervention, she blacked out under the influence of a sedative and landed in the Cedars-Sinai Medical Center psychiatric ward under an involuntary 5150 hold after she threatened to kill herself.
"It was a full-on breakdown," she tells PEOPLE, speaking about the events in detail for the first time in this week's cover story. "I was under enormous pressure."
The terrifying episode forced the actress to slow down and finally focus on getting healthy. But even that led to criticism when body bullies attacked her for gaining weight. When she first shot to stardom, "It was always, 'She's too skinny, she must be sick,'" says Barton, now 27. "Then it was, 'She's too big.' I was never the right weight."
Today, she's focusing on the positive. In addition to her new supernatural thriller I Will Follow You Into The Dark
, she filmed a TV pilot with Frankie Jonas, The Gutsy Frog
, in which she plays a crush-worthy schoolteacher. She also has a London boutique, which carries her new makeup collection, a handbag line and some her favorite clothing styles. "I've learned a lot," she says, and she's proud of her choice to finally speak out about her struggles: "I'm stronger now."
For much more from Barton's exclusive interview about how her life spun out of control, her "terrifying" breakdown and how she recovered, pick up the new issue of PEOPLE, on newsstands FridayPLUS: Watch for PEOPLE on
Katie every Thursday. Check your local listings for times.