The 31-year-old, who stars as late country singer Johnny Cash in the biopic, denies rumours his addiction had spiraled out of control, because had always been able to work despite his high alcohol intake.
Phoenix says, "To be honest I don't know how comfortable I am saying that I'm an alcoholic.
"Not because I think it's shameful, but I just don't know if it's true.
"I prefer sobriety. In the past, if I had to go to an event where there was a lot of small talk, I'd think, 'I can't handle this.'
"So I would just drink and not care. That was the extent of my alcoholism.
"When I'm working, I get very motivated, but there's part of me that loves the idea of doing nothing, and drink allows you to do nothing.
"Now I'm forced to do something more worthwhile with my friends.
"I used to think people were pussies to not drink. Now I think it's courageous."