"As a fighter it's a good thing to have it, because it makes you better because you completely obsess about being a better martial artist," St-Pierre told CBC's Wendy Mesley for The National. "Everything you do is oriented around that goal. But the same thing could be bad for a normal person in normal life."
In promoting Takedown: The DNA of GSP, a documentary about his life and career, the former UFC world welterweight says he could make a return to the sport.
"I will be happy doing it again until the obsessiveness takes over and makes me unhappy again," he said.
St-Pierre said the disorder was ultimately bad for him. He said he slept poorly for a decade — no more than five hours a night — and also saw his personal life and mental health suffer.
"It was going to drive me crazy. That's why I took that break," he said. "I had my first New Year's and Christmas with my family, a real one. I don't have to go away because I have a fight coming up."
St. Pierre is also pushing for better policing of performance enhancing drugs among UFC fighters.
He argues that the stakes are simply too high.
"If you lose a race or game in hockey, you lose a game. That's it." he said. "If you lose a fight you might lose part of your brain because of the damage."
He argues that better controls and penalties would help the sport gain legitimacy. St- Pierre said it would also make the sport more fair.
"If I'm fighting you and I give you a knife and I have no weapon, you have an advantage." he said. "It's a biological weapon."
You can watch the entire interview tonight on CBC Television's The National.