Mischa Barton on a Destructive Path, Says Pal
"She has been on a destructive path for a while now," a friend of the actress tells PEOPLE. "Her drug and alcohol [use] has gotten to a point where it drove people away."
The star of The O.C., 23, who sources say has been "dealing with a lot of personal issues," is under psychiatric evaluation at Cedars-Sinai Medical Center in Los Angeles after calling police with a health problem on Wednesday.
"I don't think she knows her limits," adds the pal.
But Barton has battled demons before: She pleaded no contest to drunken driving in April 2008. Later, she called the incident a low point and said she was disappointed in herself. In July 2008, she told Marie Claire magazine that she'd sought treatment for her problems.
"I wanted to prove to the court that I would take it completely seriously," she said, "so I went to rehab to prove I was sober."
It's not exactly clear what led the young star to be hospitalized this week, but experts say Barton could be discharged by Saturday afternoon if she demands to be released or doctors find her to be stable. If her condition doesn't improve, they can request an additional 14-day hold.
With reporting by KEN LEE