Why does weed always turn on you at some point?

I don't know a single person who has been able to smoke weed their entire life without it devolving into a paranoid and anxious existence. I feel like it's nice, it has made me appreciate sobriety a hell of a lot more, but I still miss weed. I haven't smoked in months now and even the thought of it makes me super scared. This is the case for everyone who has smoked weed that I know.

Why is this? Like, on a biological level?