I have never done, nor I condone the use of Illegal substances. The crap is bad for PERIOD. And yes it's bad for your training. Lets put it this way, I wouldn't want some guy high on dope spotting me.
In short, Drugs are for the weak. people who don't know how to, or scared to face life with a clear mind and spirit. If a person can't get high on life itself then that makes for a simple minded weak person.
That's my opion on the subject.