The harm may be subjectively or objectively measurable, transient or chronic. It can even be fatal - for example, surgical patients are reported to die on the operating table because they expect to die. In one study, says Dr. Hahn, investigators found that those who expected a heart attack were 3.7 times more likely to die from a coronary condition than those who did not expect one - independently of other known risk factors. Ultimately, researchers say, the extent and manifestation of the nocebo effect differs from culture to culture. That a patient's psychological make-up will greatly influence how he or she is affected by disease is well known.
Extreme examples are cases of voodoo death.
A young African bushman was deceived into eating wild hen, absolutely forbidden to his tribe. When he learned the truth later, he was dead within 24 hours. The helpful effects of placebos are not unrelated to effects such as voodoo death. Both are instances of the subtle links between expectation and reality. William B. Carey, director of Behavioural Pediatrics at the Children's Hospital of Philadelphia, brings important research to the public in his book Understanding Your Child's Temperament .