nocebo,
noun
A
harmless substance that that causes
harmful effects because the person taking/using it
expects to be harmed. Similar to
placebo, except that with a
nocebo a person expects to be harmed as opposed to
healed/
helped with a
placebo.
Apparently
nocebo effects, are quite
common, so
think positive!
I met this word in a Straight Dope column.
(http://www.straightdope.com/columns/001229.html)