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Healthy Balance

Full Moon Rising: An Investigation of a Myth

Full moon“Things get crazy when it’s a full moon.”

I’m sure you’ve heard it before – full moons fill hospitals: more babies are born, more people visit the emergency room. It’s the kind of conventional wisdom people talk about with unquestioned conviction – and have for years. Lunacy derives from the Latin luna, the moon. The belief that the moon messes with us is built into our language.

But I was curious: Do full moons really cause us to go crazy? And if so, why?

A cursory internet search and I found that plenty of researchers had wondered the same thing. Studies trying to link moon phases to all kinds of conditions have found – well, not much.

Not that researchers haven’t tried. It seems hundreds of studies have attempted to find statistical correlations between rates of suicide, seizures, crime and lunar phases. But the results have all been inconclusive at best.

For instance, one experiment did find the number of epileptic seizures increasing during full moons – but only when the moon was visible. No correspondence existed during heavy cloud coverage.

For help with my subsequent confusion, I turned to Mark Quigg, MD, a UVA neurologist who conducted research at the National Science Foundation’s Center for Biological Timing at UVA and continues to study and treat epilepsy and other conditions.

“I’ve had patients who swear that the moon has something to do with seizures,” Dr. Quigg said. And he had also heard the anecdotal reports of emergency room increases.

But his short answer, for whether the moon actually does affect us?


No? I asked Dr. Quigg about the study. Didn’t it prove that the full moon has an effect – of some kind?

“There have been various publications trying to link occurrences of seizures with various natural phenomenon – like the moon or the seasons,” but, he said, the real factor for seizure episodes: Time of day.

Time of Day?

Dr. Quigg explained that he and other researchers found that the time of day directly corresponds to the kind of epilepsy a patient has. For instance, people with mesial temporal lobe epilepsy are most susceptible to seizures in the afternoon.

When trying to answer why, Quigg found it has to do with the circadian timing system – our inborn, biological rhythm – which affects hormone secretion, and the hormones in turn have some influence on seizure occurrence.

How did they come to this conclusion? Dr. Quigg: “We compared humans who are asleep during the night and rats who are asleep during the day – both with the same kind of epilepsy – and found they both had seizures during late afternoon. The timing is the same between humans and rats; the underlying mechanisms and genes of the clock are the same.”

Setting the Brain Clock

So, okay: Dr. Quigg’s work explains that we have clocks in our brains that tell us what time of day it is, which regulates the secretion of hormones that govern our bodily functions, like when to go to sleep.

But back to my inquiry: How does this account for the study showing an apparent relationship between full moons and seizures?

Our biological clocks, Quigg explained, are “set by the sun. Your eyes receive the sun’s light at the same time every morning. That signal is fed back to the circadian timing system deep within the brain. So you’ve got a brain clock that runs on the 24-hour schedule. It’s this timing of the light that keeps the brain’s clock synchronized with the local environment.”

The cloud-cover study doesn’t prove the moon – its gravitational pull or the timing of its phase – causes seizures; rather, it demonstrates a relationship between seizures and nocturnal luminescence, or moonlight. Which makes sense from what I had learned from Dr. Quigg, that exposure to light from the sun sets the circadian clock, which signals the release of hormones, which in turn affects seizures.

It was all starting to make some sense.

One Last Question

I still had to know why it is that the duration of the human female’s menstrual cycle – an average of 28 days – seems to match that of the lunar cycle – which is usually 29.53 days. It seemed like evidence of something, right?

Again, the answer was no.

Dr. Quigg told me that one of the mistakes we make is to “confuse different rhythms and cycles. The sunlight’s effects on our inner waking-sleeping clock is separate from the lunar cycle, seasonal variations, monthly menstrual cycles.” He pointed out – as do several sources online, including Wikipedia – that the human menstrual cycle is not identical each time, nor does it match the exact length of the lunar phase.

The End, But Not the End

It seemed I had reached the end of the investigation. The correspondence between the moon and human menstruation is merely coincidence; the effect of the full moon on the brain is about sunlight, not the mysterious pull of the moon.

But I was far from disappointed. The romanticized notions of the lunar force may have been dispelled, but I came away with a magnified sense of awe and appreciation for the realities of life – the complex circadian rhythms, our intimate physiological relationship with light – and the science that continues to investigate the questions that never seem to end.

Are you under the influence of the moon? Tell us. The next full moon is Monday, September 12th.

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