Music and Drugs

This week's discussion board about brain processes and the link to creativity got me thinking about a problematic topic... the whole drug scene in music.  A lot of the music I listen to is interesting to me because the group produces a sound that no other group produces, which is why a lot of the stuff I like is classified as alternative and by no means mainstream.  But now that I think about it, a lot of these groups are influenced by certain drugs.  This comes as no surprise to me because before I knew exactly which drugs influence certain bands, I had a pretty good idea considering some of this stuff is too whacked to have been done by sober individuals!  For example there's a group I consider extremely creative by the name of The Mars Volta.  They are constantly on acid trips writing, recording, or playing music live.  I got to see them live at Voodoo Fest this past year which was beyond awesome, and their show was extremely creative to me because most of their stuff is improv.  The first song they played is 7 minutes and 15 seconds on their album, however, they played this song for nearly 25 minutes at the show.  Their entire hour and a half show was comprised of 5 songs... unbelievable right?  When they record they put TV's and such in the studio so if the singer is inspired by anything he sees, he just sings about it and the band knows how to follow with certain improvisations.  Every time they play one of their songs it's different and it's like they will never play the same song twice.  Each of their albums has an extremely profound story behind it, probably some of the craziest stuff I've ever heard.  This seems really creative, but if it's influenced by drugs can we really give them credit for it?  My question is, if drugs influence the creativity of the individual, or group, is the creation considered creative?  I guess I would say yes because the creation is both novel and appropriate, following the definition in our book, but then maybe not give the creators full credit...