From PEOPLE Magazine Click to enlarge
Poolside at the Four Seasons hotel in Los Angeles is a place out of movieland fantasy, where starlets preen in the sunshine and nobodies lucky enough to grab a lounge chair get a chance to stare. But on July 14 gawkers on the gleaming deck were treated to a darker Hollywood scene: that of a celebrity in free fall. A haggard young woman sat by the shimmering water, smoking cigarette after cigarette. Her face looked aged and puffy, her hair uncombed. "She seemed exhausted," says an onlooker. "And very quiet." Not so long ago, she had been somebody glamorous: Mischa Barton, the luminous teen queen from TV's The O.C. Now she was just working hard on being lost.

A day later cops responded to a call for help at Barton's L.A. home, and the 23-year-old actress wound up at Cedars-Sinai Medical Center, involuntarily held under psychiatric evaluation as a potential danger to herself or others—the same steps used to hospitalize Britney Spears after her breakdown in 2008. Authorities won't comment on the nature of the emergency that prompted the hospitalization; neither will her rep. But friends of the actress's speculate it's the inevitable result of mental anguish and serious substance abuse. "Mischa has been spiraling for two years," says a Barton pal. "Everyone's been waiting for this to happen. It's been a long time coming."

Friends and colleagues are hoping the onetime It Girl has finally hit rock bottom—so that she will get the help she desperately needs. "Mischa's friends were worried that she was suicidal," says a source who spoke to the circle of pals who were around her just before her hospitalization. "It was so frightening." After gaining fame on the teen soap, the London-born beauty struggled with intense family pressures—her mother, Nuala, is also her manager—and insecurities about her looks. She fell in with a fast-lane young Hollywood crowd, and soon her behavior alarmed even veteran partiers. Over the past two years multiple sources witnessed her drinking heavily and using drugs. A few friends say they realized she was out of control after a scary 2007 incident, when an ambulance had to be called to a Hollywood party after Barton became ill from taking drugs, according to a partygoer. (At the time Barton's rep said she had had a bad reaction to bronchitis medication.) "Ever since that party, most of her Hollywood friends have distanced themselves from her," says the pal who was there. "It was crazy and just too intense, even for that circle."

In December 2007 Barton was arrested for DUI and driving without a license. She pleaded no contest and was sentenced to three years of unsupervised probation. "That was a low point for me. I never, ever would have thought I would be arrested," Barton told Nylon last year. "It associated me with a group of girls that I would rather not be associated with." In fact former pals like Nicole Richie no longer wanted to hang around Barton. "Her darker side has really come out. Her friends like Nicole want to be supportive but can't be around her too much," says a source close to both women. "Mischa is just too screwed up on drugs and alcohol."

Recently she raised eyebrows on the London club scene, where she was spotted looking disheveled and acting erratically. Still her career profile has been its highest in months: She was set for a role in the new CW drama The Beautiful Life (production begins July 31), and her indie thriller Homecoming opened in select cities July 17. With her mother on-set with her while making Homecoming, she was "always professional," says producer Austin Stark. But others who worked with her recently noticed problems. "Every time she came into the office was like a train wreck," says a source. "In the past few years I don't think I've ever seen her when she hasn't been wired."

Many who know Barton say she was derailed by pressure to succeed. "She comes from a highly controlling mother, and while that might have helped her stay well behaved in the early days, now she is just rebelling," says a source close to the actress, who still lives with her parents and 21-year-old sister Hania in L.A. Nasty comments about her body in magazines and blogs fueled insecurity. "She had a big problem with photos of her cellulite," says a friend. Adds another: "She isn't comfortable with her body. It's been a big source of stress and self-hate."

To Barton's friends, her hospitalization came as almost a relief—and they hope she will finally defeat her demons. "She doesn't go out to have fun; she goes out to escape the pain," says a pal. "She needs serious help."

  • Contributors:
  • Reporting by David Caplan,
  • Pernilla Cedenheim,
  • Lisa Ingrassia,
  • Peter Mikelbank,
  • Eunice Oh,
  • Alyssa Shelasky,
  • Jeffrey Slonim.