How did Bridget's mom die in 'The Sisterhood of the Traveling Pants'?

She committed suicide. That's why her depression is referenced by Bridget throughout the series.

From what I read in the second book "The Second Summer of The Sisterhood", she had a mental illness and killed herself while at home.
How you may wonder?
One morning when Bridget was 11 years old she walked into her mom's room to wake her up. But she screamed when she saw her on the floor with a needle in her wrist, her blonde hair sprawled out on the floor, her skin was blueis white, and her face wasn't moving. Her dad and twin brother Perry came in to see what she was screaming about, and when they saw, they screamed and cried as well.
http://wiki.answers.com/Q/How_did_bridgets_mom_die_in_sisterhood_of_the_traveling_pants#page1