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Lightning and Migraines

Lightning and Migraines Photo Credit: By Ian Boggs from Astoria, US (Lightning on the Columbia River) [CC-BY-SA-2.0], via Wikimedia Commons

Migraine headaches are associated with lightning storms.


Transcript

A news flash about migraines. I’m Bob Hirshon and this is Science Update.

Lightning storms may trigger migraines. This according to a new report from researchers at the University of Cincinnati. Fourth-year medical student Geoffrey Martin and his colleagues asked migraine sufferers to keep a diary of headaches and other migraine symptoms for three to six months.

Martin:
And so what we found was that on days in which there was at least one lightning strike within 25 miles of a patient’s home zip code, there was a 25-30% increase in headache and in migraines.

Even when they controlled for air pressure, humidity, precipitation, and other weather factors, there was still a significant effect for lightning. Martin notes that lightning strikes create both electromagnetic radiation and pollutants like ozone, either of which could potentially trigger headaches. If the findings hold up, patients may be advised to take preventive measures whenever a storm’s expected. I’m Bob Hirshon for AAAS, the Science Society.


Making Sense of the Research

This study is useful in highlighting the difference between correlation and causation. This is a very important distinction in science. Let's use rain as a simple example. Rain causes the ground to get wet. In other words, the ground getting wet is a direct result of rain falling. 

A few features of causal relationships. 1) They're not exclusive: Rain isn't the only thing that makes the ground wet; a garden hose or a sprinkler can do it too. 2) They work in one direction: If rain causes the ground to get wet, that doesn't mean that the ground getting wet causes rain. 3) It doesn't have to apply in all situations: The ground can stay dry during a rainstorm, for example, if it's under a tent. The basic rule is that A (rain) directly affects the likelihood of B (wet ground). 

A correlation is simpler: It means that one thing varies predictably with another. For instance, umbrella use is correlated with rain. So are gray skies. But the rain itself doesn't directly cause either of these. People often decide to use umbrellas when it's raining, but the rain itself doesn't make the umbrellas appear. Gray skies are part of the same weather patterns as rain, but one doesn't cause the other. Causal relationships are a kind of correlation, but only one kind.

In the long term, scientists are often looking for causal relationships. But often, they have to start by looking for correlations. In this experiment, the authors identify a correlation between lightning strikes and migraine headaches. In order to link them, they had headache sufferers write down their symptoms every day, not knowing what they would be compared to. After receiving the diaries, the researchers compared days when symptoms occurred to days when lightning struck relatively close by—within 25 miles of the patient's home ZIP code. (They didn't make the area too small, in order to account for people traveling around as part of their daily routine.)

The result was that on lightning days, migraine sufferers were more likely to report symptoms. Furthermore, the researchers then used statistical techniques to separate out other possible causes that are correlated with lightning: low air pressure, rain, high humidity, and so on. Even with all the major storm-related factors that they could think of taken out, headaches were still more likely on days when lightning was also involved. 

Does this prove that lightning causes headaches? No, but it's a clue that suggests it's possible. The authors suggest a couple ways this could happen: for example, because lightning produces chemicals in the air that may cause headaches, or that electromagnetic radiation from lightning may trigger symptoms. It's known that lightning does both these things, but whether they have anything to do with headaches wasn't tested in this particular study. Future research, however, may take a closer look at these potential contributors.

Now try and answer these questions:

  1. What is the difference between correlation and causation?
  2. In this study, is lightning correlated with headaches, or shown to cause headaches?
  3. How can a correlation make the case that one thing may cause another?
  4. Can you think of any other phenomena in nature—weather, for instance—that are correlated, but don't cause one another?
You may want to check out the February 1, 2013, Science Update Podcast to hear further information about this Science Update and the other programs for that week. This podcast's topics include: Lightning bugs inspire LED design, a new type of light makes others look dim by comparison, and could lightning be related to migraine headaches?


Other studies that made unexpected correlations, without yet proving a causal relationship, include two studies of aggression and physical features: Asymmetry and Aggression and Finger Length.

Insect-borne illnesses like West Nile virus are related to the weather for completely different reasons. Learn more in West Nile Weather


Going Further


For Educators

Other studies that made unexpected correlations, without yet proving a causal relationship, include two studies of aggression and physical features: Asymmetry and Aggression and Finger Length.

Insect-borne illnesses like West Nile virus are related to the weather for completely different reasons. Learn more in West Nile Weather


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