Truth is, and I've seen it many times, people who become addicted to hard drugs already had a psychological problem leading to that. They don't need cannabis as a gateway drug, they go straight with paint, glue, etc.
I had a bully in junior high, you could tell the guy was poised for perdition. I had a friend who had very strong character and physically strong and they began to do many drugs together such as :
Smoke weed, swallow a 12-pack of beer each, then inhale thinner, etc. like crazy.
They tried all the drugs then did Toloache also known in Mexico as "The Devil's weed" you can read about it in Castaneda's books.
The thing is hallucinogenic but towards dark/negative shit and it is also highly toxic, it is like a poison, to the point that it actually grows in every lot in Mexico and it is not even regulated because since nobody dares to use it then people don't really look for it, don't even know it.
No only they skipped the warnings but they actually made tea/milk from so many of these plants when in reality you only need drops. Then they started using it almost daily as if it were a milkshake.
The result: The bully became absolutely insane and you find him walking barefoot in the streets.
My friend simply quit drugs as he said he didn't need them and he is healthy and strong.