i agree. look at the effects of lithium and other antipsychotics on the mentally ill. their creativity goes to pot when medicated.
to answer V's question, i think the poisoning is what enabled the specific music that beethoven produced. i have known a lot of people who can give facts and figures and speak eloquently using the proper terminology in a specific field, but they couldnt think their way out of a wet paper sack and they couldnt create something new if their life depended on it.
a muse can be anything - alcohol, sex, other drugs - but they do not make everyone brilliantly artistic. therefore the person is the one with the gift. i guess it all depends on what it takes to bring that gift out.