A shocking diary chronicling DEMI MOORE’s descent into a drug and booze hell has surfaced, and it provides insight into how a glittering screen star’s life was shattered by a brutal past and uncertain future.

The diary was found in an L.A. area dumpster five years ago, and it details the tortured world of alcohol, drugs, promiscuous sex and violent family dysfunction that Demi experienced before going into rehab in the mid- 1980s.

The explosive 80-page document, written in Demi’s hand on college-ruled paper, was shown to The ENQUIRER by the man who claims he found it.

“I was stunned when I first saw it,” he said. “No one can read her words without feeling sorry for Demi, despite her fame and fortune. “It’s jaw-dropping material – a deep look inside Demi’s hellish life.”

In the diary, Demi reveals the deepest, darkest secrets of her past – how her parents fought constantly, her early introduction into alcohol and illegal drugs, her troubled sex life and even the tragedy of losing a baby after getting pregnant by an A-list star.

“When you read these memories, it’s easy to understand why Demi is so tortured today,” said the man who found the diaries.

The ENQUIRER passed the harrowing jour­nal to two respected handwriting experts for authentication. They compared the written rehab confessions with lengthy samples of Demi’s handwriting that are widely avail­able – and confirmed – unequivocally – that the “Ghost” beauty, 49, was the author.

“Demi almost died of an overdose before going into rehab in 1985, and she nearly died of an overdose after experiencing con­vulsions from inhaling nitrous oxide from metal canisters last month,” said a family insider.

Just 22 years old at the time, Demi con­fesses that she abused booze and a laundry list of drugs.

Born to alcoholic and combative parents, Demi recalls how she began drinking beer at age 3 and experimented with marijuana on a family camping trip when she was 9.

Young Demi often found herself in the middle of fiery family arguments, which sometimes involved guns. Sadly, her fa­ther killed himself when she was 16, and Demi saved her mother Virginia from sev­eral suicide attempts.

But by 1985, Demi’s career was be­ginning to flourish. She became a member of the big screen “Brat Pack,” and began a tumultuous relationship with another young actor.

During the volatile romance, detailed in the journals, Demi says she lost a baby.

 And she almost lost her own life, as well. Just before she shot “St. Elmo’s Fire,” she went into near deadly convulsions from a cocaine overdose.

 Fortunately, director Joel Schumacher got her to enter rehab.

Now, Demi is fighting to beat demons that include the ADD prescription drug Adderall and nitrous oxide, but the struggle is the same.

Noted a family insider: “Let’s hope she recovers for good and that the new diary she works on in rehab will be her last.”