Bad Night's Sleep? It's the Lunar Cycle

It has long been thought that the full moon has an effect on humans, from influencing fertility to our mental state. In fact, the term lunatic derives from luna, the Latin word for moon.

Now researchers at the University of Basle offer scientific evidence that we do actually sleep less when the moon is at its peak, taking longer to nod off and our slumber is lighter at height of lunar cycle.

"The lunar cycle seems to influence human sleep, even when one does not 'see' the moon and is not aware of the actual moon phase," says Christian Cajochen of the Psychiatric Hospital at the university.

The researchers studied 33 volunteers in two age groups in the lab while they slept. Their brain patterns were monitored while sleeping, along with eye movements and hormone secretions.

The data  show that around the full moon, brain activity related to deep sleep dropped by 30 percent. People also took five minutes longer to fall asleep, and they slept for twenty minutes less time overall. Study participants felt as though their sleep was poorer when the moon was full, and they showed diminished levels of melatonin, a hormone known to regulate sleep and wake cycles.

"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," the researchers say.

Cajochen adds that this circalunar rhythm might be a relic from a past in which the moon could have synchronized human behaviors for reproductive or other purposes, much as it does in other animals. Today, the moon's hold over us is usually masked by the influence of electrical lighting and other aspects of modern life.

The researchers say it would be interesting to look more deeply into the anatomical location of the circalunar clock and its molecular and neuronal underpinnings. And, they say, it could turn out that the moon has power over other aspects of our behavior as well, such as our cognitive performance and our moods.

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The above story is based on the July 25,2013 news release by Cell Press. a publisher of biomedical journals, including Neuron, Immunity, Molecular Cell, Developmental Cell, Cancer Cell, Current Biology, and Cell Stem Cell and Cell Reports.

Cajochen C, Altanay-Ekici S, Münch M, Frey S, Knoblauch V, Wirz-Justice A. Evidence that the Lunar Cycle Influences Human Sleep. Current Biology, 2013; DOI: 10.1016/j.cub.2013.06.029

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Circalunar Rhythm A biorhythm that corresponds with the lunar cycle (approximately 29.5 days). The reproductive cycles of many organisms, especially marine organisms, are linked to changing levels of moonlight and the tidal cycle, both of which are governed by the phases of the moon.