Jan. 7, 2008 -- It seems no one's quite sure what set off Britney Spears' latest breakdown.
The fallen pop star spent two nights in Los Angeles' Cedars-Sinai Medical Center last week after failing to surrender her two sons to her ex-husband, Kevin Federline, initiating a three hour standoff with cops.
According to People magazine, Spears tested free of illegal drugs and alcohol at Cedars-Sinai.
"She tested clean," People's unnamed source said. "This lady is as clean as clean can be, and has been for some time."
But London's News of the World claims her bizarre behavior was the result of a "purple monster" mix of vodka, NyQuil and Red Bull, which she downed along with 100 prescription pills, including 12 Vicodins, six Ritalins and 10 sleeping pills.
After consuming that cocktail, Spears called her pregnant 16-year-old sister, Jamie Lynn, and said she'd be taking over the spotlight soon, shouting "You're not going to be the only f---ing Spears on the front cover of a magazine next week!" London's News of the World reported.
However, Paul L. Doering, professor of pharmacy practice at the University of Florida, said Spears would not have been able to stand had she taken all those drugs and chased them with alcohol, let alone make a phone call.
"I can tell you without hesitation that a human being could not ingest all of those drugs and still be on this planet," he told ABCNEWS.com. "The additive effect, the combined toxicities, the out-and-out poisonous properties of those things would send someone surely to the morgue rather than to the ER, especially if swilled down with vodka or any other alcoholic beverage."
While Spears' drug and alcohol intake is up for debate, her mental state is not. Thursday's episode is the latest in a year-and-a-half-long binge of breakdowns, which in 2007 included shaving her head bald and beating a car with an umbrella.
TV personality Dr. Phil McGraw visited Spears in the hospital and told ETonline.com that the meeting "convinced [me] more than ever that she is in dire need of both medical and psychological intervention." Though he had planned to air a special talking about Spears, the television doctor said in a statement to "Entertainment Tonight" that he'd decided to shelve it because her "situation is too intense at this time."
According to People, Spears' bizarre behavior is the result of an undiagnosed bipolar disorder. An unnamed source close to the Spears family told People "there is no question she is bipolar ... she's had manic episodes for years."
Spears' weekend activities may support that claim. Though she was described as hysterical Thursday, after checking out of Cedars-Sinai early Saturday the pop star went out to dinner with a photographer where she "seemed in a really good mood" and had a "champagne mimosa to drink," reported People magazine, quoting the restaurant manager.
While Spears was in the hospital Friday, a California Court Commission gave Federline sole physical and legal custody of their children, 2-year-old Sean Preston and 1-year-old Jayden James until Jan. 14, when another custody hearing is scheduled.