Georges St-Pierre conducted an interview with Mark Bergmann of Bloody Elbow at a promotional event for Under Armour yesterday, where the longtime UFC welterweight champion detailed his decision to leave MMA.

The main reason I left was the drug problems, the performance enhancing drug problems,” St-Pierre said. “I’ve been doing this sport at the elite level for a very long time. I’ve been champion for like nine years, eight years, and it’s a very stressful life.”

“You have a lot of criticizing, ” he continued. “You don’t wanna hear the critics sometimes, but it’s still there. I’m a sensitive guy, and it still hits you, and you’re never good enough and stuff. So for my mental health, I needed to step out and get a little bit of a social life.”

St-Pierre is continuing to train, however, but only for fun. He has made no decision about returning to MMA.

“I should have stopped maybe one fight or two fights before, but I couldn’t,” he said. “There’s always somebody challenging you, and I felt I needed to it — instead of wanting to do it.”

St-Pierre was clearer in his praise for the new anti-doping policies which were established by the UFC this year, which he called “a big progress.”

“It’s something a lot of athletes are afraid to talk about, but it’s a big problem,” St-Pierre said of PED use in MMA. “Even more in our sport than it is in other sports, like cyclists. Because in our sport, you can die, you know — or very serious damage. It needs to be checked by a very serious organization. The UFC made it with USADA, and it’s great news.”