How Did Mischa's Life Become Such A Mess?

As you know, on Wednesday night police showed up to Mischa Barton's Hollywood home to assist the actress with a “medical issue,” and shortly thereafter she was taken to Cedars-Sinai Medical Center where she was placed under an involuntary psychiatric hold (aka a 5150). Under a 5150, authorities can hold a person involuntarily if they present a danger to themselves or others, are gravely disabled or suffer from a mental disorder.

So what happened to the former it girl? Sources close to the actress are speaking out about how her hard partying lifestyle may have played a role in her current state, and it appears as though Ms. Barton may need another trip to rehab...

A source tells Star, "Mischa is so unhealthy and out of control. She’ll down anything - wine, beer, vodka - whatever she can get her hands on! Most nights she’s getting smashed until 2 or 3am. It’s sad." Another friend tells the mag, "She's partying nonstop, and it's ruining every aspect of her life. Her health, relationships and career are all going to hell. She's a train wreck, and everyone sees it." An insider for People seems to agree. "She has been dealing with a lot of personal issues. I don't know if she really ever gave up some of the bad habits that had gotten out of control a couple years back."

When Mischa stepped out in Los Angeles last week, her face appeared very bloated, but her reps blamed the puffiness on the removal of a wisdom tooth. While that seems like a legit excuse, her weight has fluctuated so much over the past 8-12 months, we don't really know what to believe! This time last year, Mischa seemed like she was at a relatively healthy weight, but in January, she debuted her new scary skinny frame in France, causing various media outlets to speculate that she had an eating disorder and/or a drug problem. We know a lot of starlets go up and down on the scale (paging Hilary Duff!) but Mischa's dramatic transformation certainly alarmed a lot of people.

What do you think happened to Mischa? Is she partying too hard, is she turning into her sister, or is she having some sort of quarter life crisis? Or all of the above?