Illegal Creativity?

While learning about Ken Kesey, we discovered he liked to... use large quanities of hard drugs in order to party, and empower his creative genius. Following our discussion in class about his drug use, Ms. Serensky said "Sadly, some people feel like they are the most creative [while on drugs]". This made me think. How many books have we read that were written under the influence? Was Harriet Jacobs tripping on acid while she wrote Incidents in the Life of a Slave Girl? Questionable, but probably not. Was Truman Capote snorting cocaine in between writing pages of In Cold Blood? Definite possibility. Or was William Shakespeare smoking a blunt (or it's old school equivalent) while he wrote Othello? Wouldn't put it past him.
     How do we know which works were completed without the help of "illegal creativity"? We will never really know. That brings me to the second point. Are people truly more creative when on drugs, or is it just a figment of their imagination? I imagine that under the influence of alchohol it may be difficult to write, not being able to find a piece of paper, a chair, or spell their own name right, I don't think large quantities of alchohol would be creatively stimulating. Pot, I could see as being helpful. Some of Bob Marley's songs are quite deep, and very creative, and we all know he and his bong were very good friends. Acid, I don't know. All I've heard about acid is that it makes you hallucinate and do crazy things. I feel like this would make you very creative, but make it also very hard to sit down and write, so in a way counter acting itself.
     I don't know if drugs are worth the amounts of creativity they provide, but I guess I'll just have to keep reading, and try and find out if my favorite books were written by people who barely remember writing them.