In an interview with The Hollywood Reporter, the Moneyball actor revealed that he used marijuana in order to "numb" himself from the depression he was dealing with as a result of his skyrocketing career.
"I got really sick of myself at the end of the 1990s - I was hiding out from the celebrity thing; I was smoking way too much dope; I was sitting on the couch and just turning into a doughnut; and I really got irritated with myself," Pitt recalled.
"I got to, 'What's the point? I know better than this'. I used to deal with depression, but I don't now, not this decade - maybe last decade. But that's also figuring out who you are. I see it as a great education, as one of the seasons or a semester - 'This semester I was majoring in depression'."
He continued: "I was doing the same thing every night and numbing myself to sleep - the same routine. Couldn't wait to get home and hide out. But that feeling of unease was growing and one night I just said, 'This is a waste'."
Pitt went on to reveal that it was a trip to Casablanca, Morocco which eventually inspired him to change his life and tackle his depression.
"I saw poverty to an extreme I had never witnessed before, and we talked about inequality and health care, and I saw just what I felt was so unnecessary, that people should have to survive in these circumstances - and the children were inflicted with a lot of deformities, and things that could have been avoided had become their sentence," he said.
"It stuck with me. I just quit. I stopped grass then - I mean, pretty much - and decided to get off the couch."
Pitt, who has been nominated in the 'Best Actor' category at the 2012 Oscars for his work in Moneyball, has insisted that it won't be weird to go up against close friend George Clooney for the prize.
Watch Brad Pitt in the trailer for Moneyball below: