Angelina Jolie's teenage years and young adulthood were marred by erratic behavior: drug-use, self-cutting and a volatile love life.

And Andrew Morton's juicy new tell-all Angelina: An Unauthorized Biography -- excerpted exclusively in the new Us Weekly -- argues that it all began with a traumatic event in the star's infancy. According to former babysitter Krisann Morel, Jolie's late mother Marcheline Bertrand virtually abandoned her baby daughter after a painful 1976 split from husband Jon Voight.

Morel claims that, for two years, Bertrand sequestered Jolie in a separate apartment in her building, where the young girl was cared for by a revolving staff.

Now 35 and a mother to six kids she shares with love Brad Pitt, Jolie has publicly declared her devotion to Bertrand, who passed away in January 2007 of cancer. But Morton writes that Jolie was permanently scarred by this early abandonment -- leading her to self-destructive acts and a "come here, now go away" personality.

For more exclusive revelations from Morton's new biography -- how Angelina seduced Leonardo DiCaprio, Ethan Hawke and others, whether she and Brad will ever wed, how Brad's mid-life crisis contributed to his split with Jen Aniston and more -- pick up the new issue of Us Weekly, out now.