I used to read forums for schizophrenics (self disorders fascinate me, look the term up if you want to understand schizophrenia), and it was the consensus there that out of all the recreational drugs cannabis caused the greatest deterioration in one's mental state. Those are generally fairly sick people, but I don't think one can just ignore this signal. I personally went catatonic once after consumption, and I'm not…
I’ll admit to feeling a bit dumber and foggier after a few weeks of ingesting cannabis nightly though. That’s a real thing.