Troubled star Lindsay Lohan made the controversial, eyebrow-raising decision to pose for Playboy - full-frontal style no less - for a very simple reason.

Or a million simple ones, to put it more accurately.

Proving she may not have killed ALL her brain cells over the years, Lohan is reportedly worried about her financial situation and possible jail sentence.

So when Hugh came a knockin', LiLo obliged.

The embattled actress is facing up to 18 months behind bars for a probation violation in her shoplifting case. A hearing has been set for November 2.

Moreover, "Lindsay still hasn't signed a contract for the Gotti biopic. Lindsay is concerned about her finances and needs the money," says a source.

"Lindsay's flow of income has greatly diminished in the last year. With jail as a possibility, she felt now was the time to do the Playboy photo shoot."

It's unclear when Playboy will unveil its Lindsay Lohan nude spread, but it's gonna be epic. The 25-year-old just completed a "tasteful" four-day shoot.

Thoughts on seeing LiLo naked in Playboy?