One friend can’t enjoy two little squares of chocolate without uttering the pleasure-defying prediction, “That’s it! Now I’m bound to get a migraine!” Another couple can’t relish a slice of plain old wheat toast and butter without delivering doomsday prophecies of bloating and exhaustion. Can a teensy bit of chocolate really cause such distress? And since when did simple food become so evil? Sorry, but I’m just not buying it. I’ve concluded that my friends are paranoid. Lovely, just paranoid.

Mind you, I’m in no position to judge. After many frustrating years spent chasing an effective migraine medication without all those seemingly inevitable nasty side-effects, I have a nice line in negative predictions myself. “Oh, great, a new drug,” I groan. “Something else to make me feel dizzy and nauseated.”

Then I heard of the ‘nocebo effect’. We’ve all heard of harnessing the power of positive thinking to aid healing. Brain imagery techniques show us that thoughts and beliefs can trigger mood shifts and even changes in the body’s biology. We know that optimism about perceived benefits can trigger a positive physical response, but it’s also true that if you expect the worst, you probably won’t be disappointed.

The term placebo, Latin for “I shall please,” was coined in the 1700s, but nocebo, which means “I will harm,” didn’t appear until the 1960s. In controlled clinical trials, a placebo is the inert substance—commonly milk powder or a saline solution—given to one unknowing group of participants while another unknowing group receives the real drug or treatment, to provide an unbiased way of studying efficacy.

The placebo response is something altogether different. It’s when our optimism and positive thinking alone triggers improvement. Its dark side, the nocebo response, is when pessimism and negative thinking triggers nasty side effects or sets us up not to be helped by a medicine or treatment. And it turns out that many studies vividly demonstrate its power.

In one, researchers gave volunteers sugar water and told them it was an emetic. Incredibly, an astonishing 80% vomited. In a nutritionist’s study, when people were fed foods to which they believed they were allergic, they all felt ill. Yet when they were fed the same things via a stomach tube without knowing it, a teensy 2% reported any ill effects.

In the early ‘80s, researchers told 34 college students that an electric current would pass through their heads and could leave them with a headache. Over two thirds of the students got a headache although not even a smidgeon of electricity was used.

In 1992’s Framingham Heart Study, a group of women who believed that they were prone to getting heart disease were almost four times as likely to die as others with similar risk factors, but without those negative and fatalistic expectations.

Just prior to the 2004 Olympics, researchers at Australia’s Southern Cross University studied the effectiveness of steroids with curious results. Participants who received a dummy pill were convinced that they suffered steroids’ infamously nasty side effects, the irritability known as ‘roid rage’, and acne. The list of studies showing the ‘nocebo effect’ goes on and on.

Dr. Elizabeth Loder, director of the Pain Rehabilitation and Headache Management programs at Massachussets’ Spaulding Rehabilitation Hospital, suspects that anxiety about eating certain foods could very well trigger headaches, rather than the foods themselves.

“People want to take action to help their headaches, rather than feeling powerless,” she explains, “and our diet is one of the few things we can control. And just about any time you have a headache you have recently eaten something. So the possibility for spurious associations to come up is just very present.”

Unfortunately, once faulty reasoning kicks in while patients search for causes, they’re often on a roll. “The way the human brain works,” Loder explains, “is that once we have a hypothesis, we tend to give extra weight to any information that supports that hypothesis and to discount or ignore things that don’t.”

Loder has found surprisingly little evidence to back up the most commonly named dietary triggers and contends that many studies involved were very poorly done. Wine and alcohol are plausible triggers; they’re vasodilators, which make blood vessels expand. But she found no good evidence that, for instance, sugar plays a part in headaches for most people.

Chocolate also has been demonized. While some studies have shown that it can trigger headaches, the most rigorous testing, Dawn Marcus’s 1997 double-blind study at the University of Pittsburgh, had a very different outcome. Marcus split 63 women who suffered a lot of tension headaches, migraines, or both, into two groups.

“One group got chocolate, the other carob,” Dr. Loder explains. “Both had been disguised with a lot of mint and Marcus said they both tasted equally awful. And they were not able to identify any difference in headaches between the two groups.”

One in five people now blame wheat and dairy foods for making them tired and bloated. And citrus fruit, dairy, and wheat are often on the lengthy list of foods deemed forbidden for headache or migraine sufferers.

“And if you take them away from healthy young women who are the biggest sufferers of migraines,” says Loder, “that’s not a benign thing. For example, folic acid, which is found in things like citrus fruits, is very important because of birth defects. So I don’t think it’s productive, without good, good reason, to put all these ideas in people’s minds.”

Pharmaceutical drug advertisements on television put plenty of ideas in our minds too by listing a litany of nasty-sounding possible side effects. Although some may be relatively rare, the companies are required to mention them by law. Just hearing them could sow the seeds for a nocebo response!

“When you’re looking for adverse reactions in a study,” says Dr. Robert Temple of the FDA’s Center for Drug Evaluation and Research, “you can either ask for people to spontaneously provide them to you, or you give them a checklist. You always get more responses from a checklist. “Oh, yeah, I did have a loose stool!” So if something’s on people’s minds, they may be more likely to report it than otherwise.”

Sleep specialist, John Herman, PhD, FCCP contends that the nocebo phenomenon is, “A core component of insomnia. Cognitive behavioral therapy of insomnia begins by attempting to dispel negative beliefs, such as "I've got to get 8 hours sleep," or, "If I can't fall (or fall back) asleep, tomorrow will be ruined.”

Herman, a psychiatry professor and director of the Sleep Disorders Center for Children at Dallas’s Children’s Medical Center, explains that what is known as psycho-physiological insomnia is based on the idea that worry instills chronic somatic tension in the neuromuscular system and the sympathetic nervous system. That then interferes with the ability to sleep. Herman has noticed an interesting phenomenon when patients show up at a sleep lab determined to stay awake so the doctors will witness their problem:

“As a result of this reversed expectation, "I am going to stay awake" instead of "I have to get to sleep", the patient falls asleep rapidly and sleeps soundly. One such patient believed it was the laboratory room and the electrodes that helped him sleep.

“He was very wealthy and asked if he could buy the laboratory room and its equipment to help him sleep. He actually paid to return to the sleep laboratory on some occasions when he needed a good night’s sleep.”

People with a history of disappointing outcomes with medication and treatment, or with anxiety or depression, are especially vulnerable to the nocebo phenomenon. Yet take comfort: just knowing about it may be the best weapon of all. And one more very good reason to learn to think positive.

(Southwest Airlines’ Spirit magazine published a version of this story.)

Sue Russell
Sue Russell