Is The Moon Affecting Your Sleep? is reader-supported. We may earn a commission through products purchased using links on this page.

The relationship between human behavior and the phases of
the moon has long been the stuff of legend and folklore. Werewolves aside,
cultures throughout history have paid great attention—and celebration—to lunar
phases.  Beliefs about a connection
between some of our most basic biological processes—including sleep—have also
been common. But, scientific evidence showing connection between human sleep
and lunar cycles? That’s not something we’ve seen.

Until now.
Lunar phases

Swiss scientists conducted a study
that suggests
sleep is significantly affected by lunar phases. Their results show changes to
sleep throughout the moon’s 29.5-day cycle, and significant increases to sleep
disruption during the time immediately surrounding the full moon. 

The story of how these results came to be is almost as
interesting as the findings themselves. The conditions of the experiment—which
was conducted by scientists at Switzerland’s University of Basel—were well
suited to isolating a possible relationship between lunar phases and sleep.
During study periods, volunteers slept in a highly controlled laboratory
environment, which removed them from any direct visual contact with the moon,
and controlled exposure to nighttime light. They were given no indications
about time of day. Participants prepared for the study by having their sleep
routines regulated before the study period even began: for a week before
in-laboratory sleep sessions, volunteers maintained a strict sleep-wake
schedule and pattern of exposure to light and dark. They also abstained from
both caffeine and alcohol. But perhaps the most significant control measure
occurred without any planning at all. The
researchers did not decide to use the study data for a lunar-sleep analysis
until several years after the experiment itself had concluded.
(The idea to
compare their sleep-lab to moon phases happened over drinks at a local bar—on
the night of a full moon.) As a result, none of the people involved with the
study—from the participants to the laboratory technicians to the scientists
themselves—were aware that the data gathered would be used to investigate a
connection between sleep and the phases of the moon. As with any scientific
inquiry, knowledge about the questions being asked can have an influence on the
course of the experiment, and the outcome. 

To investigate possible links between our sleep and the
phases within the cycle of the moon, investigators returned to their earlier
experiment, which included 33 volunteers. Participants came from two different
age groups: 17 men and women were between the ages 20-31, and the remaining 16
were men and women ages 57-74. All were nonsmokers in good health, without
medical or psychiatric conditions. None took any medications.  All participants were good sleepers, and were
screened for sleep disorders and sleep quality. 

Over a 3-year period, volunteers spent a series of 3.5-days
in laboratory sleep sessions. During these laboratory sleep sessions,
researchers collected information on several aspects of sleep, including:

  • Sleep
    latency (the time it takes to fall asleep)
  • Overall
    sleep time
  • Time
    spent in REM sleep and slow-wave sleep
  • Brain
    activity during slow wave sleep
  • Nighttime
    melatonin levels 

When researchers analyzed their data in relation to the
phases of the moon, they found sleep changed significantly throughout the lunar
cycle, with disruptions to sleep peaking during the days closest to the full

  • Sleep
    latency increased as the full moon approached. On the nights of a full
    moon, it took people an average of 5 minutes longer to fall asleep. After
    the full moon passed, sleep latency began to decrease.
  • People
    spent 30% less time in slow-wave sleep—the deepest phase of sleep—at the
    full moon. As the full moon arrived, EEG scans showed brain activity
    during slow-wave sleep diminished.
  • Melatonin
    levels dropped during the days surrounding the full moon, with nighttime
    melatonin levels at their lowest on full-moon nights
  • Overall
    sleep time also dropped to their lowest levels—an average of 20 minutes
    less sleep—on nights with a full moon.
  • Volunteers
    reported their lowest sleep quality during the full moon phase of the
    lunar cycle. 

What’s behind this connection between our sleep and the
cycle of the moon? That ultimately remains something of a mystery—but
scientists have some ideas, based on other research linking animal physiology
to lunar cycles. As researchers point out, the answer does not lie with forces
of gravity. The moon’s gravitational force has effects on earth, specifically
and most overtly on ocean tides. But the gravitational impact of the moon does
not have an explicit effect on the human body. Researchers suggest that we may
carry within us an internal biological rhythm that is linked to the moon’s
cycle. Researchers liken this approximately 30-day “circalunar rhythm” to our
circadian rhythms, which regulate several biological functions—including
sleep—on a 24-hour cycle, in basic alignment with night and day. Other
scientific research has demonstrated links between the phases of the moon and
several species of marine
life, indicating in these animals the presence of “circalunar clocks” that work
in conjunction with
their circadian clocks.  

This is a fascinating and potentially important breakthrough
in our understanding of the biological processes of sleep. We still have so
much to learn about why we sleep, and how sleep works. Results like these point
us in new and exciting directions, thanks to the curiosity of this group of
scientists. Somebody buy these folks another round! 


Sweet Dreams,

Michael J. Breus, PhD 
The Sleep Doctor®

The Sleep Doctor’s Diet
Plan:  Lose Weight Through Better Sleep

Everything you do, you do better with a good night’s sleep™ 
twitter: @thesleepdoctor  @sleepdrteam

Image courtesy of siraphat at


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Michael Breus, Ph.D - The Sleep Doctor is a Diplomate of the American Board of Sleep Medicine and a Fellow of The American Academy of Sleep Medicine and one of only 168 psychologists to pass the Sleep Medical Specialty Board without going to medical school. Dr. Breus is a sought after lecturer and his knowledge is shared daily in major national media worldwide including Today, Dr. Oz, Oprah, and for fourteen years as the sleep expert on WebMD. Dr. Breus is the bestselling author of The Power of When, The Sleep Doctor’s Diet Plan and Good Night!

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