I start by admitting that I smoke (tobacco), even when I know that it is health damaging. I used to drink a lot too, now I'm a rather social drinker (most of the times). So, I know my share of addictions. No finger-pointing here and no preaching, just facts. THC is a mild sedative and low in the addictions' scale. So it's not as big a problem as alcohol or other drugs. If you do like it, I'm not the person to suggest you quit, if you play poker legit, you are an adult and you know better than I the facts of your habbit and how -if it does- it affects your life.
Only point I want to make is that, although it might help you blunt the edge a bit, this is not a long term solution for poker playing. You need to have a very clear head in order to play your a-game, so substances, addictive or not, even food that is hard to digest should stay out of the equasion.
In short: Smoke pot if you like -and if you don't mind the legal aspects- but don't smoke for poker.