So why does the THC cause paranoia and hyper activity? I thought it mellowed people out.
It's the dose. Smoking a lot will cause "paranoia" too. Actually I think the paranoia is what weed does, it's part of the effect, not a side effect really, but people interpret it differently. Some feel they dwell on negative stuff but others feel it just stimulates philosophical thought. Weed can make me feel relaxed and happy but at the same time there is always an undercurrent of anxiety present. But you can deal with it, just observe it in a mindfulness sort of way.
It's also well know the THC paranoia, which is part and parcel of its effects, is modulated by the other constituents of the plant, like CBD. Some products might even have pure synthetic THC added. Some have described the effect of pure THC as if you went to a funeral, very unpleasant.
A very common reason for stopping or pausing weed is "uncomfortable or unwanted thoughts," your perception of your life problems is enhanced. That's why some say weed isn't always an escape - your problems might seem bigger in fact.
Matt said he had a hellish experience and would rather take heroin if he had to choose. But I sure he could negotiate the cannabis effect by starting with a very low dose, he could still enjoy it.
It's also interesting that anti-anxuety meds like benzos almost completely abolishes any negative mental effects BUT also abolishes the positive high too. My theory is that the paranoia IS the principal effect.