Does the moon influence the human body? (next full moon? July 2)

Does the moon influence the human body?

The question has stirred for ages, and a group of scientists in Switzerland recently reported that they’ve found evidence (they called it “statistically significant”) that human sleep suffers during a full moon. The study, though well controlled, was small (just 33 individuals) and skeptics were quick to challenge their claims (Fred Turek, a chronobiologist at Northwestern University, told NPR: "Extraordinary claims require extraordinary evidence" and the new study, said Turek, falls far short of providing that evidence).

Nonetheless, the scientists’ claims were noteworthy. Said the study report: “We found that around the full moon, EEG delta activity during NREM sleep, an indicator of deep sleep, decreased by 30%, time to fall asleep increased by 5 minutes, and EEG-assessed total sleep duration was reduced by 20 minutes.” So less total sleep, diminished deep sleep and lower melatonin levels. 

The researchers, led by Christian Cajochen, who studies circadian rhythms and sleep at the University of Basel, added: “. . . to our knowledge, this is the first report of a lunar influence on objective sleep parameters such as EEG activity during NREM sleep and a hormonal marker of the circadian timing system (melatonin) in humans . . . .”  They went on: “This is the first reliable evidence that a lunar rhythm can modulate sleep structure in humans when measured under the highly controlled conditions of a circadian laboratory study protocol without time cues.”  In other words, the subjects were in lab rooms for days on end, without any cues from natural light.

Author Niall McCrae, in a piece written for www.theconversation.com, noted: “. . . [T]he results suggest that humans might have an innate circalunar rhythm, that is, a body clock of physiological activity with a length that roughly correlates to the length of the lunar cycle (29.5 days).” Quoting the study, McCrae said that “at full moon, the peak in melatonin levels was delayed by around 50 minutes.” Concluded McCrae, author of a book on the moon and its influence on mental illness: “Christian Cajochen and fellow chronobiologists [have] provided perhaps the strongest indication yet that the moon really does affect the mind.”

Do animals have a circalunar clock?  Cajochen and colleagues cited recent research which found such a clock in a marine midge. “This circalunar clock is thought to tick inside many animals, running in synchrony with the tides and working in conjunction with the animals’ circadian clock.” The researchers cited a study by Wilelski and Hau which “found that those Galapagos marine iguanas with the most accurate circalunar clock were most likely to survive tough times, presumably because they were the best at reaching feeding spots first . . . . ”

So, while Cajochen and fellow chronobiologists keep looking for answers (said the report: “It remains challenging to unravel the neuronal underpinnings of such a putative lunar clock in humans”), you might consider going to bed a touch earlier this Thursday, July 2. After all, it’s a full moon.

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