Mystic Moon

The idea that the phases of the moon are linked to the human psyche is one of the oldest and most pervasive examples of folk lore and mythology. It is woven into the fabric of our classic literature, poetry and music. Even today, a surprising number of people believe that our deepest emotions and mental states are influenced by the lunar cycle, and there are plenty of police officers, doctors, nurses and prison guards who would swear blind they’ve seen evidence of it in their everyday lives. 

But is the lunar effect real? How and why does it work? Humans have spent thousands of years discussing the lunar effect in stories and legends, and the last 40 years documenting it in the academic literature. So what’s the verdict? How does the moon affect us?

In it’s simplest form, the Werewolf exemplifies our most primitive understanding of a link between human behaviour and emotion and the moon. It captures our idea that during the full moon, man becomes wild, violent and instinctive, a reversion to a more basal, less civilised version of ourselves. This is probably the most pervasive aspect of the myth, that the moon controls human aggression, impulsivity, violence and mood. 

But the lunar effect has also been proposed for a range of scenarios so broad it will make your mind boggle. A quick google search will tell you that the moon controls our fertility and reproduction, influences violent crime, suicide and even traffic accidents, affects seizures, blood loss, sleep quality and even our political leanings. All of this begs the question, how and why might such a mechanism exist?

How Might the Lunar Effect Work ?
Biological rhythms are common and usually controlled by hormonal changes, which are in part regulated by external stimuli such as light or temperature. In marine animals, circalunar cycles (following a lunar cycle of 29.5 days) are well documented. This is hardly surprising since the tides are heavily influenced by the lunar cycle – if you live in the water it makes sense to be in tune with it. Many marine species that sleep in the open also experience huge variation in light availability at night which may influence their biological rhythms. Other studies have found that the lunar cycle is correlated with hormonal changes in insects, fish and birds.

At a purely mechanistic level, a number of hypotheses have been proposed to explain how the moon is able to influence us. It is commonly said that water is the underlying link between physiology and the lunar cycle – the external stimulus of the lunar effect. The logic goes that if the moon exerts a tidal force on bodies of water such as seas, then it will also exert a small force on water in our bodies. This common misconception is an error of scale – the tidal force is actually extremely weak, far weaker even than the gravitational force exerted on a human by a mosquito flying close. 

Plus, the tidal force of the moon depends on its distance from the Earth, not its phase – the moon’s elliptical orbit takes just 27.5 days not 29.5 (the lunar cycle). Higher tides at the full and new moon occur not because tides are linked to the phases of the moon, but because at these times the Sun, Earth and Moon are aligned, increasing the tidal force. Oh yeah, and the tidal effect only works on unbounded bodies of water – the water inside your body is definitely bounded !

So, water isn’t responsible for the lunar effect. Other hypothesised triggers include electromagnetic radiation, gravitational pull, positive ions and polarisation of lunar light. There is no solid evidence for any of them, and some of the suggestions are downright stupid. What about the internal control of this hypothetical lunar effect? Several hormones have been implicated in regulating an internal lunar cycle, including melatonin, and corticosterone and other endogenous steroids. 

In fish, the lunar clock influences reproduction through hormonal changes initiated in the hypothalamus-pituitary-gonadal axis. Similarly, birds show daily fluctuations in melatonin and coricosterone, hormones involved in stress and sleep, which disappear during the full moon. Finally, one study has shown that the lunar cycle influences taste sensitivity in lab rats, mediated by the ultrastructure of the pineal gland. However, despite ample evidence for lunar periodicity in behaviour and physiology in animals, there is no convincing evidence for its existence in humans.

Why Might the Lunar Effect Occur ?
Aside from the mechanism, what would be the purpose and benefit of evolving such a system for lunar control over the body? Biological rhythms are well documented in nature; animals, plants, even bacteria show strong daily and seasonal patterns of behaviour and physiology. It is known that these are linked both to external stimuli such as temperature and light, as well as an internal clock. These rhythms are of huge evolutionary benefit, allowing organisms to remain in sync with the day-night cycle of predator and prey activity, and annual variations in climate and food availability. Could a similar process explain the lunar effect?

Avoiding Predators.
One hypothesis is that if predators such as lions and sabre-toothed cats were influenced by the phases of the moon, then it would also have paid for early humans to respond to these phases. Africa lions alter their hunting behaviour in response to moonlight, and are most dangerous when the moon is faint or not visible. This is likely to be largely due to the additional light provided by the moon, making humans more vulnerable to predation during a new moon.

Aggression, Crime and Mental Health.
What about human behaviour? The lunar effect has been linked to the occurrence of homicides, suicides, fatal traffic accidents, aggravated assaults and emergency room visits. In 2007, senior police officers in Brighton announced that research had found a correlation between violent crime and the full moon [citation needed], and planned to deploy more officers in response. Similarly, rises in crime have been blamed on the full moon in Ohio and Kentucky, and in New Zealand, Justice Minister Annette King suggested in 2008 that a recent spate of stabbings might relate to the full moon. As scientists rushed to study the claims empirically, some early studies found a correlation between the occurrence of abnormal behaviour and the lunar phase.

One study found a significant relationship between psychopathology and quality of life and the full moon in schizophrenic patients, however this relationship was not present for other mental health patients, and other studies have failed to find a relationship between human behaviour and the lunar cycle. For example, in Sydney, psychiatric patients show similar levels of violence and aggression throughout the lunar cycle, and a meta-analysis of 37 studies found that the lunar effect accounted for less than 1% of variation in behaviours termed ‘lunacy’. 

They found no effect of the lunar cycle on mental hospital admissions, psychiatric disturbances or crisis calls. A meta-analysis of 20 studies investigating the influence of the moon on suicide rates found that the majority of studies failed to find an effect; those that did show an effect were not consistent with one another, a classic sign of spurious statistics.

Further, there seems to be no discernible link between crime and the moon. Although one study in the early 1970s reported lunar periodicities in homicides, suicides, traffic accidents and assaults, closer inspection of the data revealed flawed statistical methods – the pattern did not hold up to statistical re-evaluation. Since then, an analysis of nearly 5000 crisis center telephone calls has showed no evidence for the lunar effect and less than 1% of variation in call frequency was explained by the lunar cycle. 

Despite this, crisis center workers reported a greater belief in lunar effects than people working in other jobs, suggesting the lunar effect may be a result of attribution and confirmation bias. Meta-analyses have also failed to find any effect of lunar cycle on homicides or other criminal offences.

Other Lunar Effects.
There are some other, much stranger, things that have been linked to the lunar effect – absenteeism from work, alcoholism, electoral decisions, somnambulism (sleep walking) and even lycanthropy (werewolfism). One bizarrely common myth is that surgeons do not perform surgery on the full moon because it causes increased blood loss. Some suggest that this effect is mediated through the moon’s influence on the water in our bloodstream. 

However, there is no logic behind this claim, nor any robust statistical evidence to support it, and surgeons definitely do still operate, successfully, on full moon days and nights. One study investigated the influence of the full moon on nose bleeds and found there was no difference in their at the full moon, so that type of bleeding certainly seems to be unaffected. Another commonly cited effect of the lunar cycle is on seizures and epilepsy, however few studies have provided empirical evidence. One study found that nonepileptic seizures were more common during a full moon, but found no effect on epileptic seizures.

It seems wherever we look, we find a lot of anecdotal fuss about lunar effects that just doesn’t seem to hold up to empirical testing. So where does the full moon myth come from, then ? We will never know...