Van Gogh was more than likely manic depressive. And the effects of alcohol (absinthe has a high alcohol content) and depression most likely drove him to chop off his ear......lobe, not the thujone in the absinthe (no way to no for sure though).
For more info check out the link to the thread in MICAH67's post above.
To learn about buying a bottle go here:
http://www.sepulchritude.com/chapelperilous/absinthe/