The 42-year-old actress achieved great success in the 90s, including being nominated for the Best Supporting Actress Oscar for her role in 1997 film 'Good Will Hunting', but she admits she wasn't prepared for the glare of the spotlight.
She said: "I definitely went a bit bonkers in my early 20s, when I got famous quite quickly. Bonkers in a way where I didn't eat enough, I drank too much coffee, smoked too many cigarettes, cried a lot and was very emotional."
Minnie was pulled out of this difficult stage of her life by her sister, model-and-producer Kate, who told she was "acting like an idiot".
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In an interview with Stylist magazine, the 'Hunky Dory' star revealed: "My sister showed up one day and said, 'I don't recognise you. You weigh seven stone and you're behaving like an idiot.' I came back to England and sorted myself out. Hollywood is portrayed in this super glamorous way, but when I see pictures of actresses going off the rails, it doesn't surprise me at all. You have to have solid family and friends."
Minnie - who has a three-year-old son, Henry - is now documenting her experiences in an autobiography.
She hopes the book will show people what it's really like to be an actress in Hollywood.
She said: "I'm working on a memoir about my childhood and getting famous, It's an interesting journey to tell if you haven't dissolved into drugs and alcohol. I want to tell it from the view of someone who was normal, but whose life became abnormal."