PHOTOS: Mischa Barton Buys Alcohol On First Sighting Since Drug-Fueled Meltdown

As RadarOnline.com previously reported, Barton was rushed to the hospital for a mental evaluation after cops were called to her home last Thursday.

But according to sources, the starlet's big scare is no surprise. "Mischa has been on this downward spiral for years now," an insider told RadarOnline.com exclusively. "Her attempts at getting healthy have always failed. She took on Dancing With The Stars to make some money and try to clean up her act — but that didn't help. She ended up purposely getting booted off the show because she couldn't handle it. She hated the show, she hated the work involved and really wanted to keep partying."

As reported, the star was reportedly spotted in her backyard hanging over the fence, babbling about her mother and spitting out "incoherent statements." Her concerned neighbors called 9-1-1 and the Sheriff’s deputies and firefighters responded. The neighbors reported it was a jumper or a possible overdose.

Later, Barton alleged that someone had slipped her the drug GBH, telling PEOPLE, “On the evening of the 25th, I went out with a group of friends to celebrate my birthday. While having drinks, I realized that something was not right as my behavior was becoming erratic and continued to intensify over the next several hours."

But this incident is just one of many. "I was with her a few times in the past year or so. One time was at a dinner party and she was doing mushrooms! Not the kind you eat either. Who does shrooms at a dinner party?" an insider revealed to RadarOnline.com. "Then, just two weeks later, she was at a bar in NYC and smoking pot and doing coke. She was openly using her hand to snort coke off of in this tiny space."

Now, those close to Barton hope she'll finally get her act together following her hospital visit. "I really hope this is THE wake up call she needs," said RadarOnline.com's source. "She has a horrible relationship with her mom — she's pretty much alone in LA. She's broke and hasn't been able to get it together to start making money again. Every time she attempts any sort of come back she ends up shooting herself in the foot and not being able to follow through. It's not just the partying either. She struggles with depression and she self medicated with the partying so when she hits bottom she hits hard."