I think the correct word is called "depersonalization" and i've had that too, hence why I stopped smoking weed. I agree it has to do with depression that is caused from smoking a lot of cannibis. I had been smoking pretty heavily for a year and a 1/2 and all together about 3 years in total on and off. Anyway, when I get really stoned, I would have that feeling that everything was kind of fake. Like I was looking through some type of viewfinder and perceiving the world all different. One time we smoked a fat blunt in my friends backyard right after school and I remember looking at everyone and having this weird thought about how they were perceiving everything and i felt trapped like the sky was over us and it's hard to explain but it bothered me. I was looking at his dog and I was like what the fuck, how does a dog perceive things, especially since that dog is sober. I couldn't contemplate how the world worked and how it was to be sober. It wasn't like scary it was weird and yeah it really is unexplainable, but I think i know what your talking about.