If a person truly believes that a sugar pill can ease pain, it probably will. If you believe that expensive, name-brand drugs will work better than cheap generics with the same ingredients, they probably will—for you. Scientists call this the placebo effect. According to Utne Reader’s September-October issue, “sincere belief triggers bona fide reactions in the brain.”
The same power can also be harnessed to hurt people. If a person believes something will harm them, rational or not, the belief can destroy a person’s health, according to Brain Blogger. This phenomenon, called “nocebo” effect, has been little studied, in part because of ethical concerns for patients. Brain Blogger reports that there is plenty of anecdotal evidence to prove the nocebo effect’s existence: People have died after receiving a terminal diagnosis, when a post mortem examination revealed that the diagnosis was wrong. The effect could also explain the power of hexes and voodoo curses.
Sources: Brain Blogger