Does the Full Moon Make People Crazy?

Separating Full Moon Fact from Folklore

Tim Clark
Full Moon

Can the Moon change your luck? Or, make people act strangely? Science doesn’t have proof, but could centuries of folklore be wrong? Unless you plan to ask a werewolf (which we don’t recommend), it might be time to explore the myths and reality.

The Lunar Connection

Ancient authorities like Aristotle, Paracelsus, and Pliny the Elder thought some humans were driven crazy by the full Moon. The Latin name for the Moon—“Luna”—is the root of modern words like “lunacy,” “lunatic,” and even “loon,” as in “crazy as a loon.” 

Even today, many doctors, nurses, EMTs, police officers, and elementary school teachers agree that full Moons will bring bizarre behavior—43 percent of healthcare professionals believe in what some call “the lunar influence,” as do 81 percent of mental healthcare specialists. But is there really a lunar connection to abnormal behavior?


Science says no. Hundreds of studies have failed to turn up evidence of the lunar influence. And those few studies that suggest a connection are usually disproved or contradicted by others:

  • one study says more animal bites (from cats, rats, dogs, horses) occur at the full Moon
  • another says there’s no increase in dog bites
  • one shows an increase in crime around the full Moon
  • others find no increase in arrests, calls for police assistance, prison assaults, batteries, or homicides
  • admissions for psychosis are lowest during the full Moon, and psychiatric emergency room visits decline
  • calls to suicide prevention hotlines peak at the new Moon, not the full Moon

One explanation might be what psychologists call “confirmation bias”—people are more likely to notice things that confirm a preexisting belief. If you’re working in an emergency room, and something weird happens on the full Moon, your older and wiser colleagues nod and say, “Must be a full Moon.” That’s what they heard from their elders when they were new at the job. (Psychologists have a name for that, too: “communal reinforcement.”)


But if something weird happens at a different phase of the lunar cycle, nobody says, “Must be the third quarter Moon!” And when nothing unusual happens on the full Moon, nobody says anything.

We call widespread beliefs that are unsupported by fact folklore. Erika Brady, who teaches folklore at Western Kentucky University, says, “it’s a way of imposing order on something that feels frighteningly out of control.”

How does a belief that strange things happen on the full Moon help us feel safer? The full Moon occurs only once every 29.5 days; that means the other four weeks of the lunar month should be less dangerous and unpredictable. See when the next full Moon is.

Therefore, this folk belief implies that our fears about everything from increased bleeding to werewolves may be limited to only 12 or 13 days per year.

Hey! Maybe that’s why the number 13 worries people!

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Reader Comments

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Full Moon effects

As a career Mariner, I finally retired with a new hobby (gardening). The Full moon effect creates the highest & lowest tides of the months. The human body is said to be 98% water. Of course the Full Moon effects humans.

Watermelons are 92% water.

Watermelons are 92% water. How does the moon affect them? The logic has to apply to all organisms.

Full Moon

I have worked in a nursing home for years & yes the Full Moon Does affect people.

Lunar vs. circadian rhythms


I came across two publications in 2013:

Dina Fine Maron, "Phased Out: Human Sleep Patterns Linked to Full Moon," Scientific American, 2013-07-25

Christian Cajochen et al., "Evidence that the Lunar Cycle Influences Human Sleep," Current Biology, Volume 23, Issue 15, pp. 1485–1488, 2013-08-05

Please let me know if there have been further studies on this topic.

Thank you!

Best Regards,



I agree with you. I worked on a skilled nursing unit and noticed the same thing.

Moods/Moon/ Nursing Homes

Oops. Replied to wrong comment.