Holly Madison seriously considered killing herself while living in the Playboy Mansion.

Madison reveals a darker side to living with the now 89-year-old Hugh Hefner - "a man who was old enough to be my grandfather" - in her new book, "Down the Rabbit Hole: Curious Adventures and Cautionary Tales of a Former Playboy," according to People.

She fell into a depression that led to suicidal thoughts soon after she moved into the mansion in 2002. "Would anyone even miss me?" the 35-year-old Madison once thought. "If I just my head under water and take a deep breath in, it would all be over."

The former Playboy bunny started to look at her new home as a prison where the "infamous metal gate" wasn't meant to keep people out as much as it was "meant to lock mein," she says.

Madison also admits that she and her fellow bunnies simply were going through the motions and not really living the "incredibly glamorous" life that played through on their reality show, "The Girls Next Door."

In 2008, Madison broke up with Hefner but continued to shoot the E! reality show with Kendra Wilkinson and Bridget Marquardt for a sixth and final season. Five years later, she gave birth to her daughter, Rainbow Aurora, with Pasquale Rotella, who she married a few months later.

"Down the Rabbit Hole" will hit shelves on June 23.