Lunacy

How much effect does the moon have on crime rates?

31st May 2018

I don’t know if everyone’s school life was the same, but when lessons started to get a bit rowdy, my teachers would often blame it on the full moon. Maybe they were lying, maybe they had found a link between years of misbehaviour and the moon’s cycle or maybe they were keeping very accurate and cross-referenced lunar calendars.

This is actually a well-documented phenomenon, known as the Lunar Effect. Dating as far back as the ancient Babylonians and Assyrians, people have believed that the moon has a large impact on human behaviour and physiology. A surviving fragment of Babylonian text states, “A woman is fertile according to the moon” — a misconception that is still widely believed today. While the menstrual cycle averages at about 28.5 days, the moon has no proven effect on this and scientists regard it most likely as just a coincidence.

These ancient beliefs were also held by philosophers Aristotle and Pliny the Elder, who both believed that, due to the fact that the brain was the “moistest” organ of the body, it was susceptible to the powers of the moon, like the tides. However, this is easily disproven, simply by observing a pond or lake that is too small to be affected by the moon’s gravitational pull. Don’t worry, our tiny minds are safe from moon-control.

Superstitions take hold everywhere, even in the most logical of places. A self-confessed “idiot” judged his buying and selling of shares on the stock exchange based on the phases of the moon and apparently made a sizeable profit. It could be a coincidence, but maybe Randall Ashbourne made a connection that no-one has ever found before. I guess you’ll have to buy his book to find out. Funny that.

In eight out of 12 months of 2017, the number of arrests during a full moon was higher than average

Using police data, we decided to find out for ourselves whether the full moon has any effect on human behaviour and found some interesting results.

moon data
Data: Metropolitan Police

In London, it is clear that the number of arrests made on a full moon is mostly above the average number of arrests for that month. In eight out of 12 months of 2017, the number of arrests during a full moon was higher than average. This suggests that the full moon does actually have some kind of impact on behaviour — but doesn’t explain why.

It’s not necessarily down to mood, though; it could be a placebo effect where people who think the moon alters behaviour play up to it, consciously or subconsciously.

Another reason that more arrests are made on a full moon could be that the night is simply brighter.

This would lead to more crime potentially being seen and reported and, therefore, more arrests being made. Then again, London is a bustling city filled with streetlights, so the moon’s effect would be limited.

However, The Overtake also found that in rural Wales, the number of arrests made on a full moon was consistently above average in the winter months. November, December and January all boasted an above average number of arrests on the days of a full moon, whereas the full moons in summer months of June and August had a below average number of arrests.

Brighton police department employed extra police officers to prowl the streets when the full moon was shining

With little light pollution, perhaps the long winter nights were illuminated by the full moon and more crimes were seen on the Welsh streets.

The police services who supplied us with the data were not able to say why the full moon has an effect on crime, and with no conclusive evidence that the moon has a biological effect on humans, scientists have simply closed the case of lunar-influenced lunacy and moved on to their next research.

Whichever explanation for the arrests you subscribe to, police can be pretty cautious when it comes to the full moon effect. Even as little as ten years ago, Brighton police department employed extra police officers to prowl the streets when the full moon was shining and it seems like they were on to something.

31st May 2018