It causes brain damage and it's not recommended for use until age 25, so the brain has time to fully develop. Steve Jobs and Bill Gates smoked weed, so it's not like you can blame poor performance on cannabis alone.
Leafly.com is a very informative website for inquiring minds about Cannabis. Apparently, "marijuana" is racist to some, so Cannabis is preferred name to the social justice warriors. I don't find the word "marijuana" racist, but the word has propaganda history in the banning of it's use, similar to "booze" I'm guessing.
This is why they want people to say, Cannabis, instead of Marijuana. It's sort of a white wash of all the years of lies, that was promoted to the masses.