Uck... I can't say what you should do... but I will not EVER touch that or any other drug for that matter. I have seen what drugs do to people first hand. No thanks...
If you see what I mean, you are getting a lot of emotional reaction to your question. While I agree that Cannabis should not be abused, it should not be lumped together with manufactured narcotics or even prescription pharmaceuticals. And as to a previous poster who made a comment about Aikido being designed to free you from "Modern technology" or something like that, it should be noted that Cannabis is a naturally occurring medicinal herb that predates modern medicine.
And so it should be treated as such, it should not be used "recreationally"; as I stated, if you have to ask, don't go to the dojo under the influence.
Let me also go slightly off-topic, for a good cause here. There is a current medical "fad" of prescribing anti-anxiety medications for a variety of real and concocted "conditions". These drugs have been documented to cause or worsen psychosis. No doubt many of the posters in this thread would not object to Aikidoka showing up for training under the influence of these pharmaceuticals.
I generally suggest Aikido as an alternative to this sort of treatment. In my experience, Aikido training has a profound effect on mental as well as physical health.
It is absolutely correct that dependence on "drugs" leads to negative states. But better that we emphasize that Aikido training is a higher high than any chemical, when one starts to develop ki, and I personally consider it the closest thing to a panacea.