Asthma attacks can be scary and painful—yet some of them may be avoidable if asthma sufferers can alter their expectations. Evidence is mounting that believing an odor or activity will trigger an asthma attack is sometimes all it takes to induce real physical symptoms.

In one recent study, 17 patients with moderate, persistent asthma took whiffs of a nonirritating odorant. For some patients the bottle was labeled “asthmogenic”; for others the label read “therapeutic.” The researchers monitored their rate of exhaled nitric oxide, a marker of airway inflammation. Nitric oxide levels did not change at all among the group who thought the smell was therapeutic, but those who believed it to be asthmogenic had an immediate rise in exhaled nitric oxide that continued to climb. Just after exposure, levels had risen by 36 percent; two hours later they were 56 percent higher, and the next day levels were elevated by 65 percent. “We hope to convince both asthmatics and the physicians who treat them that their beliefs alone can bring about adverse responses,” says co-author Pamela Dalton, a cognitive psychologist at the Monell Chemical Senses Center in Philadelphia.

These results align with previous findings. A study published in 2012 in the Journal of Asthma found that when asthma patients merely looked at pictures of known allergens, they reported 15 percent more symptoms than when they viewed neutral images. Other studies have shown that asthma patients experience more constricted airways than healthy control subjects in response to emotional stimuli. “Patients' perception of symptoms might be based on learned associations more than on the actual state of their lung function,” explains Andreas von Leupoldt, a researcher now at the University of Leuven in Belgium, who co-authored the 2012 study. These associations can arise through experience (such as an allergic reaction after playing with a cat) or be based on a doctor's advice (that exposure to cats may cause an allergic reaction, for example).

Taken together, the findings suggest that certain activities, odors and images may elicit a stress response that causes physiological symptoms in asthma patients. The researchers hope that doctors and public health associations will tweak their messages to asthma sufferers so that they do not overreact to experiences that may be harmless. Von Leupoldt suggests that treatments should change: if a patient complains of increased symptoms but a lung function test does not reveal any changes, a doctor might see if other factors are influencing symptoms, such as anxiety or high stress levels. “This knowledge could give asthmatics more control over how they are affected by their environment,” Dalton adds.

From Mind to Matter

Many physical maladies can be triggered by negative expectations, a phenomenon known as the nocebo effect.

  • Headache. Being told you are at risk for a headache, for instance, at high altitudes can alter chemical pathways in the brain and cause a real headache.
  • Itch. Visual cues or verbal suggestions, such as being told you were exposed to poison ivy, can make you feel itchy.
  • Allergies. Seeing, smelling or even imagining something you are allergic to can trigger a reaction.
  • Pain. Expecting that something will hurt increases your perception of the pain.
  • Erectile dysfunction. Learning that you may be prone to erectile dysfunction increases the chances it will happen. —Victoria Stern