Creativity and mental illness are linked (see Miller's Spent, earlier results in http://www.news.harvard.edu/gazette/2003/10.23/01-creativity.html ); to the extent a drug reduces inhibition, one would expect that too. (I say 'a drug' because it's easy to think of drugs which might increase inhibition and reduce creativity: Adderall and amphetamines are frequently accused of destroying original thinking and promoting a pernicious focus. One wonders what benefit Erdos realized from amphetamines - did he have plenty of good ideas but simply didn't work them out without amphetamines?)

Insanity in mathematicians seems likely to be overrated - even in the most prominent, where one would expect mental illness to be most prominent based on the average/extreme model, the rates seems quite reasonable and fairly similar to the general population: http://blog.computationalcomplexity.org/2011/07/disproofing-myth-that-many-early.html

EDIT: One sequence of images that always interested me was http://www.cowboybooks.com.au/html/acidtrip1.html - the drawings degenerate as the LSD takes hold, but some of them struck me as much more interesting and attractive than the first one, like http://www.cowboybooks.com.au/html/acidtrip6.html