Alongside various other spiritual and religious beliefs, the lunar effect is perennially lumped into the category of ‘magical thinking’ by sceptics, atheists, and scientists alike. However, one doesn’t have to look far to find anecdotal stories about strange events and heightened crime occurring on the monthly full moon. But do these claims stand up to scrutiny? Is there really any correlation between the planetary system and the outcomes or experiences for humans living on Earth?

As a teen, I found star signs fascinating, and once, whilst at a used bookstore, stumbled across a book on auras. For those unaware, an aura is supposedly a band of light (energy) around your body, which takes on various colours depending on personality traits. The colour outlines such traits as an individual’s talents, possible career pathways, likes, dislikes, financial capability, what they were like as children, what they will be like as parents, and so on. To find your aura, you just answer a series of questions and see which category you best fit into. Sounds a bit hippy-dippy suss, right? Right. I never believed that there was a band of coloured energy around my body, but, admittedly, I’m still baffled at the accuracy of aura mythology in detailing an individual’s personality in such accurate ways. Is it possible that there are only a small handful of distinct types of personalities into which we all fit? While star signs are often vague and ambiguous, the aura descriptions appeared to match each person, in great depth, with almost perfect accuracy. However, I have always thought of them as little more than very pithy personality types.

Those of you who have ever read a description of your star sign characteristics may have noticed that the description will often match up with some of your traits, yet not others – essentially, they are just vague enough for some individuals to be convinced. Star sign characteristics therefore exemplify the Barnum effect, where people will give high accuracy ratings to descriptions which they believe to be tailored specifically for them, but that are in actual fact general enough to apply to anyone. The effect has been demonstrated time and time again, with large groups of people all being given the same, ambiguous personality descriptor, and on average rating its accuracy very high.

Interestingly enough, there have been studies that have found that the level of testosterone a woman produces during pregnancy can affect the personality traits of her child. One specifically found that testosterone during pregnancy can affect an individual’s internal vs external ‘locus of control’, which is the extent to which a person believes (or does not believe) that things which happen to them are controlled by external forces. These forces include things such as religious or astrological beliefs – funny! Clearly though, this does not explain character traits being linked to birth dates, as testosterone production has not been linked to seasons. Other studies, however, have linked which season babies are born into certain personality traits and even the development of mental illnesses later in life. Whilst there are various theories speculating as to why this may be the case – such as diet differing throughout the year due to variations in available produce, vitamin D exposure, or even variations in temperature – no cross-cultural studies have yet been undertaken to causally evaluate these findings on a global scale.

Well, what about the full moon effect? Is there any truth to the planetary system affecting things such as homicide rates, mood swings, suicides, major disasters, and other types of violence? The average woman gets about 13 menstrual periods a year, meaning that women’s cycles follow the lunar calendar more closely than our current Gregorian calendar. While I have known nurses, child protection practitioners, and sex workers, who have all maintained that emergencies and violent events occur more frequently on the full moon, this suggestion remains unproven. After all, confirmation bias allows us to reinforce existing beliefs to the detriment of objective reality. To date, every analysis of historical data seeking evidence of the full moon effect has come up short.

So what does this all mean? Aren’t beliefs in things such as the full moon effect and astrology just harmless fun? Some would argue not. Many atheists and sceptics, among others, vehemently deride things that promote or lead to ‘magical thinking’: the attribution of causality to things which cannot be justified by reason or observation, such as praying in order to affect outcomes. Many argue that being open to ideas without grounding in science can lead to harm, such as using homeopathic products to treat serious illnesses, or not immunising children. However, this claim may be exaggerated – after all, many of us played with Ouija boards as children, and surely we’ll go on to make rational health choices as adults (hopefully…).

Cultural mythology can be mesmerising and fascinating, so finding out that there is little merit to the stories is pretty disappointing. However, whilst discovering that the full moon is just another day on the calendar might not seem quite as exciting as Minority–Report-style crime prediction, there are many other spacey things happening right now, many of which are worth getting excited about. As a teenager I would read my horoscope; these days, when I wear my top with the planetary system on it, or my galaxy print leggings, I think instead of technological accomplishments, like the Hadron Collider, or future scientific endeavours, such as the Mars One project, which humanity is striving towards. There’s nothing wrong with imagination, but rather than blindly letting our beliefs guide us, let’s instead use them to discover, innovate, and so guide our own future.