"The influence of negative expectation — of fear — on our health is known as the nocebo effect."

"Walter Kennedy, a British doctor and drug expert, first used the term in 1961, to describe the opposite of the better-known, more benign 'placebo.' ('Placebo' means 'I will please,' in Latin; 'nocebo' means 'I will harm.') Most researchers agree that the way we react to spurious worrying information is not dissimilar to how we respond to a sugar pill. The nocebo effect is most often observed in connection with the side effects of drugs, cases in which self-fulfilling prophecies are common. During a 2003 trial of beta-blockers, one group of male patients was told that a drug could cause erectile dysfunction, while another group was not. After three months, thirty-two per cent of those in the first group complained of erectile problems, compared with three per cent in the second. In 2007, the maker of Eltroxin, a thyroid-replacement drug distributed in New Zealand, moved its manufacture from Canada to Germany. The active ingredients in the drug remained the same, but the new pills were larger and a different color. After the media reported that the new drug was cheaper to make, reports of side effects rose by a factor of two thousand. Whether a nocebo can kill is an open question. In the seventies, oncologists in Australia and the U.S. reported cases of patients dying before their cancers were sufficiently advanced to end their lives."

From "The Psychiatrist Who Believed People Could Tell the Future/After a national disaster, a British doctor began collecting foreboding visions. Soon, they closed in on him" by Sam Knight in The New Yorker.