A devastated Lindsay Lohan has failed her first court-mandated drug test, sources confirmed to PopEater on Friday.

"Lindsay cannot believe this is happening," a source close to Lohan tells me. "It's like she learned nothing from her time in prison and rehab. Now we're all terrified that she could go back to jail."

The terms of Lohan's probation make it very clear that she'll get 30 days in jail for a positive test result--leaving her family and friends terrified about what is going to happen next.

"If anyone around Lindsay was in denial, that has all changed now," a Lohan family friend tells me. "People suffering from addiction need constant help and not everyone around Lindsay admitted she had a problem. She was staying out late in LA as soon as she left rehab and while in New York this past Saturday night, she was seen out at The Boom Boom Room with a hoard of girls until 2:15 am."