The 39-year-old had top 10 UK chart hits in the noughties with I Wanna Love You Forever, These Boots Are Made For Walkin’ and With You.
In an excerpt of her new memoir Open Book, published in People magazine, she admitted to self-medicating for years to deal with the “trauma”.
“I was killing myself with all the drinking and pills,” she said.
Simpson quit drinking alcohol in November 2017 when she realised it was “making things worse”.
“Giving up the alcohol was easy,” she went on. “I was mad at that bottle. At how it allowed me to stay complacent and numb.”
The abuse she suffered began when she was six years old when she shared a bed with the daughter of a family friend.
“It would start with tickling my back and then go into things that were extremely uncomfortable,” she wrote.
“I wanted to tell my parents. I was the victim but somehow I felt in the wrong.”