The guy can't get it up because he's worried about getting it up. That insecurity can actually cause a guy to not be able to get it up. Looking to "Chinese" medicine is as effective as looking towards placebos for a cure. If it works, it's all in his head.
Oh, and if "over-masturbation" could cause death, then all men would have a lifespan of about... 26 years
Bottom line: I think he's very depressed, and is trying to avoid that issue. I'd look to treating the depression as a first measure, as he is your friend.