Was Scooby Doo on drugs?

We're not saying he was. But look at all the evidence.

Shaggy would take "Scooby snacks" and give one to the dog. Then look what would happen. He'd think the dog was talking to him. Then they'd get the munchies. Then they'd get paranoid and start seeing "ghosts" when there was really a simple explanation for what they were witnessing.

They were obviously addicted as they kept on after the "snacks".
And they spent all their time in the back of the van together. That weird trippy sign on the side is a hint as well.