Does a Full Moon Actually Affect Our Behavior?

drawing of various halloween things, a full moon, a cat, pumpkins

Verywell / Madelyn Goodnight

Key Takeaways

  • For centuries, the full moon has been blamed for surges in crime and bizarre human behavior.
  • Despite repeated dismissal of this theory by scientists and research, superstitions persist.
  • With its cultural and spiritual significance, it could be argued that the moon can shape conscious behavior.

"It must be a full moon."

How often do we use that phrase when we encounter careless drivers on the road, unruly subway riders or generally bizarre behavior? It's a tradition that dates back to the first century when both Greek philosopher Aristotle and Roman historian Pliny the Elder hypothesized that a full moon induced madness across the land it illuminated. In fact, "lunatic" comes from the Latin lunaticus, for "of the moon" or "moonstruck".

Despite centuries of blaming the moon for mischief, mood swings and mystical occurrences, scientific research on the subject continues to point toward mere correlation rather than causation. So, why do many of us hold onto this belief?

Realistically, any "effect" the moon has on us might be linked to our ancestors. But its incredible significance within certain spiritual practices and rituals both ancient and new-age, as well as its ties to folklore, myths, urban legends, and Halloween means that despite what the science shows us, some still choose to believe in the power of the moon.

Source of Superstition

In that centuries-old hypothesis, Aristotle and Pliny the Elder believed that because the brain is moist, it could therefore be affected in the same ways that the waters of Earth are affected by the moon. They believed a moon had the power to induce insanity, epilepsy, or bouts of madness.

Even some modern thinkers toyed with this idea. Psychiatrist Arnold Lieber, MD, dug deeper into this belief with his books, "The Lunar Effect: Biological Tides and Human Emotions", written in 1978, and "How the Moon Affects You: A Compelling and Controversial Book on the Moon's Awesome Power to Affect Your Emotions and the Way You Live".

Lieber suggested that because the human body is about 70% water, humans experience tidal shifts caused by the moon's phases, just like Earth's oceans. He wrote that under a full moon, the occurrence of murder, suicide, aggravated assault, psychiatric emergencies, and fatal auto accidents increase dramatically.

While the theory seems reasonable at first glance, it was quickly dismissed by experts. One study took down Lieber's theory specifically, arguing that the earth's gravitational pull is 5,012 times stronger than the moon's, whose pull is no more than the weight of a flea. The moon might regulate the tides of large, open bodies of water, but think about its effect on a glass of water or a bathtub, let alone the water that makes up the human body.

Astronomers, physicists, and psychologists have all come to the conclusion that human behavior is not related to the lunar phase.

In 1985, researchers conducted a meta-analysis of 37 studies comparing lunar cycles to instances of crisis center calls, suicides, crimes, and psychiatric issues. The results show no relation between the full moon and any increase in these occurrences. Several modern studies echo these findings by establishing no connection between the full moon and psychiatric admissions, hospital admissions, or aggressive behavior. A study conducted in Finland even found that less homicides were committed during the full moon.

If the science tells us the connection doesn't exist, why do superstitions persist?

Lunar-Conscious Behavior

If a belief sticks (for the most part) for thousands of years, there must be something there. A recent article in Discover magazine suggested that the lunar lunacy effect originates from the fact that a brighter moon was probably more likely to disrupt our ancestors' sleep quality, causing sleep deprivation and sour moods. Today, some evidence has been discovered that indicates sleep is impacted by the lunar cycle. So perhaps that provides some explanation for behavioral changes.

Amy Morin, LCSW

It may be that the expectation that things get 'a little weird' around a full-time actually becomes a self-fulfilling prophecy. People might start acting a little differently because they believe they are supposed to act out of the ordinary.

— Amy Morin, LCSW

But many experts interpret strong beliefs about the moon's effect as illusory correlation or confirmation bias, in which we pay greater attention to the events that support our beliefs versus the ones that don't. We're more likely to take note of something strange happening when there's a full moon, and that sticks in our memory.

Amy Morin, LCSW and Editor-in-Chief of Verywell Mind says, "It may be that the expectation that things get 'a little weird' around a full-time actually becomes a self-fulfilling prophecy. People might start acting a little differently because they believe they are supposed to act out of the ordinary."

Whether the moon has an invisible impact on human behavior or not, there's something to be said for the conscious ways in which humans behave in alignment with the lunar cycle.

Among indigenous cultures around the world, the moon holds great significance. In the U.S., early Native Americans acknowledged that Grandmother Moon regulated the tides and watched over the waters of Earth, and full moons were important for tracking the passing year, which is why certain full moons have specific names that vary from tribe to tribe. Honoring the moon through ritual and dances of gratitude remain an important practice and connection to nature.

The moon holds spiritual significance for other groups, as well. As a major player in astrology, the lunation cycle is believed to heavily influence behaviors and moods. The moon is often associated with the subconscious, and if you've ever investigated your birth chart, you'll recognize that your "moon sign", which correlates with the moon's location in the sky at the exact moment you were born, is thought to tell you about your emotions and intuition.

Mindfully syncing with the moon's phases can be a powerful spiritual and self-care tool, as well. Every 29.5 days, the moon completes a full cycle, and each phase of that cycle corresponds with particular actions that vary among cultures. For example, it is believed that full moons are a time for self-reflection, while new moon are an opportunity to set intentions.

Although science has debunked many myths surrounding the moon, still people hold onto those facets of folklore that disregard a need for proof. You might not be able to blame the full moon for bad driving or awkward interactions, but being mindful of its presence can positively impact your conscious behaviors. There's also nothing wrong with embracing the spooky vibes of a full moon in October—it's those scary stories and mystery of the season that makes Halloween so much fun.

What This Means For You

There's potential for the full moon to affect your sleep cycle, but extensive research has disproven popular myths of erratic behavior and crime surrounding this lunar phase.

11 Sources
Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Garfinkle RA. The moon in mankind’s history and lore. Luna Cognita. Published online 2020. doi:10.1007/978-1-4939-1664-1_1

  2. Lieber AL, Agel J. The Lunar Effect: Biological Tides and Human Emotions. Dell Pub. Co; 1978.

  3. Sheldon G, Prunckun H. When the full moon rises over the Sunshine State: A quantitative evaluation of Queensland police calls. International Journal of Criminal Justice Sciences. 2017;12(1). doi:110.5281/zenodo.345722

  4. Rotton J, Kelly IW. Much ado about the full moon: a meta-analysis of lunar-lunacy research. Psychological Bulletin. 1985;97(2).

  5. Gupta R, Nolan D, Bux D, Schneeberger A. Is it the moon? Effects of the lunar cycle on psychiatric admissions, discharges and length of stay. Swiss Med Wkly. 2019. doi:10.4414/smw.2019.20070

  6. Margot J. No Evidence of Purported Lunar Effect on Hospital Admission Rates or Birth Rates. Nurs Res. 2015;64(3):168-175. doi:10.1097/nnr.0000000000000086

  7. Simón A. No effect of the full moon-supermoon on the aggressive behavior of incarcerated convicts: nailing the coffin shut on the Transylvania effect (the myth of the full moon affecting human behavior). Biol Rhythm Res. 2017;49(2):165-168. doi:10.1080/09291016.2017.1354799

  8. Näyhä S. Lunar cycle in homicides: a population-based time series study in Finland. BMJ Open. 2019;9(1):e022759. doi:10.1136/bmjopen-2018-022759

  9. Vyazovskiy V, Foster R. Sleep: A Biological Stimulus from Our Nearest Celestial Neighbor?Current Biology. 2014;24(12):R557-R560. doi:10.1016/j.cub.2014.05.027

  10. Theriault N, Leduc T, Mitchell A, Rubis JM, Jacobs Gaehowako N. Living protocols: remaking worlds in the face of extinction. Social & Cultural Geography. 2019;21(7). doi:10.1080/14649365.2019.1619821

  11. Lunar and Planetary Institute. Sky Tellers - Moon Phases.