Some jokes can make you laugh until you cry. Some jokes can kill. And, research shows that thoughts alone can have equally devastating consequences as well.

From BBC:

Beware the scaremongers. Like a witch doctor’s spell, their words might be spreading modern plagues.

We have long known that expectations of a malady can be as dangerous as a virus. In the same way that voodoo shamans could harm their victims through the power of suggestion, priming someone to think they are ill can often produce the actual symptoms of a disease. Vomiting, dizziness, headaches, and even death, could be triggered through belief alone. It’s called the “nocebo effect”.

But it is now becoming clear just how easily those dangerous beliefs can spread through gossip and hearsay – with potent effect. It may be the reason why certain houses seem cursed with illness, and why people living near wind turbines report puzzling outbreaks of dizziness, insomnia and vomiting. If you have ever felt “fluey” after a vaccination, believed your cell phone was giving you a headache, or suffered an inexplicable food allergy, you may have also fallen victim to a nocebo jinx. “The nocebo effect shows the brain’s power,” says Dimos Mitsikostas, from Athens Naval Hospital in Greece. “And we cannot fully explain it.”

A killer joke

Doctors have long known that beliefs can be deadly – as demonstrated by a rather nasty student prank that went horribly wrong. The 18th Century Viennese medic, Erich Menninger von Lerchenthal, describes how students at his medical school picked on a much-disliked assistant. Planning to teach him a lesson, they sprung upon him before announcing that he was about to be decapitated. Blindfolding him, they bowed his head onto the chopping block, before dropping a wet cloth on his neck. Convinced it was the kiss of a steel blade, the poor man “died on the spot”.

While anecdotes like this abound, modern researchers had mostly focused on the mind’s ability to heal, not harm – the “placebo effect”, from the Latin for “I will please”. Every clinical trial now randomly assigns patients to either a real drug, or a placebo in the form of an inert pill. The patient doesn’t know which they are taking, and even those taking the inert drug tend to show some improvement – thanks to their faith in the treatment.

Yet alongside the benefits, people taking placebos often report puzzling side effects – nausea, headaches, or pain – that are unlikely to come from an inert tablet. The problem is that people in a clinical trial are given exactly the same health warnings whether they are taking the real drug or the placebo – and somehow, the expectation of the symptoms can produce physical manifestations in some placebo takers. “It’s a consistent phenomenon, but medicine has never really dealt with it,” says Ted Kaptchuk at Harvard Medical School.

Over the last 10 years, doctors have shown that this nocebo effect – Latin for “I will harm” – is very common. Reviewing the literature, Mitsikostas has so far documented strong nocebo effects in many treatments for headache, multiple sclerosis, and depression. In trials for Parkinson’s disease, as many as 65% report adverse events as a result of their placebo. “And around one out of 10 treated will drop out of a trial because of nocebo, which is pretty high,” he says.

Although many of the side-effects are somewhat subjective – like nausea or pain – nocebo responses do occasionally show up as rashes and skin complaints, and they are sometimes detectable on physiological tests too. “It’s unbelievable – they are taking sugar pills and when you measure liver enzymes, they are elevated,” says Mitsikostas.

And for those who think these side effects are somehow “deliberately” willed or imagined, measures of nerve activity following nocebo treatment have shown that the spinal cord begins responding to heightened painbefore conscious deliberation would even be possible.

Consider the near fatal case of “Mr A”, reported by doctor Roy Reeves in 2007. Mr A was suffering from depression when he consumed a whole bottle of pills. Regretting his decision, Mr A rushed to ER, and promptly collapsed at reception. It looked serious; his blood pressure had plummeted, and he was hyperventilating; he was immediately given intravenous fluids. Yet blood tests could find no trace of the drug in his system. Four hours later, another doctor arrived to inform Reeves that the man had been in the placebo arm of a drugs trial; he had “overdosed” on sugar tablets. Upon hearing the news, the relieved Mr A soon recovered.

We can never know whether the nocebo effect would have actually killed Mr A, though Fabrizio Benedetti at the University of Turin Medical School thinks it is certainly possible. He has scanned subjects’ brains as they undergo nocebo suggestions, which seems to set off a chain of activation in the hypothalamus, and the pituitary and adrenal glands – areas that deal with extreme threats to our body. If your fear and belief were strong enough, the resulting cocktail of hormones could be deadly, he says.

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