Does the Full Moon Really Make People Crazy?

On a single Saturday night in October of 1983, the city of Montreal experienced a wave of violent crime that was beyond most people’s notions of “coincidence.”

Firstly, a man attempting to break into an apartment pulled a knife on police, and was shot. Then, on the other side of town, three men received horrific stab wounds while protecting their friend from another violent group. Finally, an all-in brawl of 50 erupted across several stations along the city’s metro lines, leading to numerous smashed windows and large chunks of concrete being thrown onto railway tracks. But the thing the media jumped on—the defining commonality between all cases—was that they all happened beneath a full white moon.

The following day the Montreal Gazette ran an interview with Lieutenant Jacques DeSerres of the Montreal Urban Community Police Department. When asked for his opinion on full moons and crime he provided a perfectly titillating quote: “As a general rule, there is an increase in crime when the moon is full… in all categories.”

Of course, Lieutenant Jacques DeSerres hadn’t coined a new branch of lunar criminology. He’d simply referenced an ancient piece of folklore: that full moons affect human behaviour.

Writing around 2,000 years ago, the Roman naturalist and philosopher Pliny the Elder theorised that the full moon affected the moisture within the brain, and subsequently human emotion. Then in the 17th and 18th centuries—and despite the renaissance era’s move away from raw superstition—physicians such as Richard Mead and James Gibbs argued that certain periods of the solar and lunar cycle induced certain conditions, such as epilepsy, scrofula and hysteria.

. In fact, the term “lunacy” is derived from the latin word for moon: “luna”.

These days popular wisdom still clings to the idea that the moon’s orbital position affects mood. As the University of Kentucky revealed in a 1987 study, 80 percent of emergency department nurses and 64 percent of the emergency physicians believe the moon affects their patients.

But does it, really?

According to Eric Chudler, a neuroscientist and research associate professor at the University of Washington, the answer is a deeply emphatic… almost certainly not. Eric is the kind of academic who speaks bluntly and succinctly, but without ever managing to deliver a straight yes or no. He is willing to say, however, that the overwhelming majority of evidence indicates there’s zero effect.

As a neuroscientist, Eric was always being asked "How does the moon manage to affect our brains?" Finally, he decided to study the existing correlative research, going as far back as the 1960s. This includes the aforementioned study into paramedics, as well as several more on policing. And what he found was that out of all the scientifically robust studies—those that involved actual peer reviews and placebos and large sample sizes—not one of them found a link. In fact, the only ones to find a correlation were riddled with questionable methodologies or overlooked obvious truths. For example, the notion that full moons motivate crime and antisocial behaviour by floodlighting cities, overlooks the fact that cities have been lit by street lamps for the past 100 years.

“You never hear about the reports where there’s a negative effect. You only hear about the one day [where there were] a lot of crimes in one city, so the police decided to put more police on the street,” Eric explains. “So do you think there’d be more arrests during that time? Well, of course there would be!”

A 1984 meta-analysis of 37 lunar effect studies found a similar effect, citing that half of the affirmative studies possessed statistical errors. One such study found an increase of traffic accidents during full moons, without accounting for the fact that those full moons coincided with weekends where people were statistically more likely to drink.

Eric says that until a hypothesis or a direct explanation as to how the moon actually affects us is provided, any change in behaviour during that time is purely coincidental. He does sympathise with the need to grab on to an explanation, though, suggesting it may help understand an unexplainable event, like police and the trauma of random violence.

Now, let’s pause for a moment to consider that there are people who swear by the moon’s influence, and many of these people are intelligent, rational individuals. For them the moon’s effects can’t be measured by science, but rather their own experiences.

One such person is Brooklyn-based astrologer Sandy Sitron. For 25 years she swears she’s observed lunar effect and other astrological phenomenons, and she can tell 2000-odd stories of her friends, family, and clients all experiencing the power of the full moon.

“[If] I was the only person who thought this way, then I’d think I was out on a limb [but] my whole community [believes this],” Sandy explains. “There are lots of people willing to respond because of this anecdotal evidence.”

Sandy is a full-time astrologer who was first being exposed to lunar psychology by her stepmother. Her apartment/office features only a handful of books and other mystical accoutrements. She’s eloquent and intelligent, discussing the complexities and differences within astrology alongside her mental log of the moon’s effects.

Sandy explains that moods are dictated by the sun and moon’s proximity to one another. At the new moon, our energy is at our lowest, before rising and ultimately peaking during the full moon—something Sandy herself experiences every month.

When Sandy was younger, before she worked full-time as an astrologer, she was a bartender. She says that in that job she saw the lunar effect in action again and again: with the moon bringing in a lot of customers, and the new moon making for slower nights.

“If it was a full moon on a Saturday night, it was great because I’d make money. If it was a new moon, we’d close up early.”

But Sandy claims she isn’t oblivious to scientific reason. Throughout our chat, she reiterates how she’s open to science and the idea that she’s wrong. Furthermore, Sandy has read the research for herself. For her, the lack of conclusive data and presence of conflicting data doesn’t mean a non-correlation—but rather it indicates how astrology is something unmeasurable by science.

“[We] have science to thank for our understanding of the world and our quality of life, but it is limited…There are lots of things that exist outside of that [provable paradigm].”

Later, I leave Sandy’s apartment feeling intrigued but unswayed. Because to me, being unable to explain the mechanism behind the effect is a big flaw. Anecdotes are cute. But they’re notoriously vulnerable to statistical coincidence, or illusory correlation.

As Scott Lilienfeld, the professor of psychology at Emory University, later told me over the phone: “The human mind will tend to remember events rather than non-events. As a result, when there is a full moon and something unusual happens, it sticks in our heads.”

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