Ha, I've attempted to try LSD once. It either did absolutely nothing for me, or whoever gave it to me was pulling my leg and just handed me a regular piece of cardboard to suck on.
I don't condone the use of drugs (and many other topics in my stories), but I do incorporate some of my own experiences in my writing, yes. In this case Marlow's experience is mostly based on what I imagine an LSD-like trip could be like, reinforced by my own experiences with narcotics.