She made the demonic cry after scrawling the devil's number "666" across her head.
Spears's manic behaviour has concerned relatives who once again fear for her safety, and has staff at the Promises Clinic in Malibu, California struggling to cope.
The ordeal began when she terrified staff by writing the number of the beast on her head and running around the clinic screaming, "I am the anti-christ!"
"The clinic people just didn't know what to do," a friend claimed.
The pop star then tried to hang herself with a bedsheet was but was found before she could hurt herself.