Olympic gold medallist Ian Thorpe has revealed that he suffers from "crippling depression" and has also battled alcohol abuse during his life.

The 29-year-old Australian, who won five gold and three silver medals at the 2000 and 2004 Games, has opened up about his struggles in his upcoming book, This is Me: The Autobiography.

"Not even my family is aware that I've spent a lot of my life battling what I can only describe as a crippling depression," he writes.

"I used alcohol as a means to rid my head of terrible thoughts, as a way of managing my moods - but I did it behind closed doors, where many depressed people choose to fight their demons before they realise they can't do it without help.

"There were numerous occasions, particularly between 2002 and 2004 as I trained to defend my Olympic titles in Athens, that I abused myself this way - always alone and in a mist of disgrace."

Thorpe recently worked for the BBC as a swimming pundit during the London Olympics.