The actor appeared to suffered a highly public breakdown following an incident at a New York City hotel in 2010, when he was alleged to have trashed his suite and held an escort hostage during a search for his missing watch.
He went on to become embroiled in a public feud with bosses of his hit TV show, who eventually fired him over his erratic behaviour, which included a series of bizarre media interviews and an ill-fated U.S. comedy tour.
However, Sheen has now dismissed long-running rumours that drink and drugs were to blame for his wild antics.
During an interview with David Letterman, the U.S. TV host asked Sheen what caused his troubles and he replied, ""Here's the confusing part. I wish it was crack cocaine. It wish it was an ocean of vodka, a bathtub full of pills. It was just my brain was kind of separated into itself. I just had to take a stand for what I know was right.""
When asked whether he was taking drugs during his meltdown, Sheen added, ""Not during the meltdown. During the previous 30 years of my life... I'm sure it looked like I was going to spontaneously combust at any moment. It was an adrenaline ride. I think it was mostly fuelled by anger.""
Sheen has previously struggled with drugs in the past and during the height of his 2011 meltdown, the actor boasted: ""I probably took more (drugs) than anybody could survive... I was banging seven-gram rocks (cocaine) and finishing them because that's how I roll; I have one speed, one gear - go!""