I've got some.
A childhood friend of mine came back from Vietnam smoking dope all day long. It's lasted to this day. He can't/won't quit. He doesn't drink because it interferes with his 'buzz'. He's lost his wife and kids and quite a few of his friends, including me, and now his oldest son is a little drug head himself and, of course, pop can't say anything to him.
In addition to that, my first wife was a pothead. Over the last 20 years she's been to doctors, rehab, etc. 45 years old and still smoking dope.
I'm sure that you will discount my evidence as 'random and rare, biased observations', but these two people are hooked and I don't give a damn what kind of evidence that you have to the contrary, it won't diminish their addition.
I believe you. If your friend is addicted, he's addicted, but it's not chemical. Some people also break open a bucket of ice cream when they get depressed, but ice cream isn't chemically addictive either.
"They" aren't "making" pot more addictive because it isn't physically addictive to begin with. Psychologically? For a very small minority, yes. Just as are certain types of food, gambling, and numerous other things. If your friend and your first wife hadn't gotten "hooked" on pot, they probably would have found alcohol or something else.