It has the effect of the existential dread of being alone with your thoughts.

That has nothing to do with addiction.

I disagree, i think it’s the basis of a lot of addiction.

There is psychological addiction and chemical addiction. Both suck, and you are likely better off gradually decreasing the activity/drug in both cases, but there is a real difference that in the latter case you must gradually decrease it, else you will have very severe side-effects, for example with alcohol it is called delirium tremens.

Of course it has. Just because it isn't directly based in a physiological reaction doesn't make it less real. And it is in general a mistake to make a clear distinction between what is mind and what is matter. They are the same.