I've heard conflicting reports about marijuana aggrivating bipolar disorder, or any psychotic or schizophrenic disorder for that matter, but I have a theory on this. I don't think it's necessarily the THC itself, or even the LSD, psilocybin, or whatever else. I think it's the trip itself. I've found from personal experience that when I had out of control, totally tripping balls experiences (mostly with cannabis oddly enough), the consequences on my own cognition were much worse (though temporary) the next day. I suspect it's the power of the trip, the blast of seratonin and other chemicals during the process, that actually has the potential to cause damage. Just a theory of course.

So yeah, I'd recommend if you are one of those rare people like I used to be who can completely trip balls on weed, to lay off a bit and have smaller doses.

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"Nirvana is the extinction of self" - Buddha