I smoke weed all of the time.
Sometimes when I smoke weed I study and I'm on another level and I'm following my chess book and actually learning.
Other times I smoke weed and I can't even see a checkmate in one move.
I'm sure the brain cells we are killing will hurt us in the long run as far as chess goes.
For speed chess definately not however for prolonged games I have found less mistakes with strategic moves...