Guest Author - Barbara Melville

The “lunar effect” refers to the Moon’s influence on humans. Over five decades of research have shown nothing to substantiate a causative link between the Moon and areas such as mental illness, birth rates, crime or accidents. However, these beliefs remain popular, and this continued fascination is perhaps in part why it hasn’t been laid to rest.

When the Moon is full, it is reflecting more light from the Sun. It is sometimes closer to the Earth but this is not conditional on the Moon’s phase. There is no rational reason to think the lunar phase is linked to human behavior, but the ideas, probably rooted in folklore, are perpetuated by anecdotal evidence in the media. This may come across as believable but it is not scientifically credible.

There are a great many theories about the lunar effect. The Moon causes the tides – surely that force has an affect on people? Aren’t we full of water too? Actually, the Moon’s tidal force is incredibly weak. Looking specifically at water theories, Skeptic Dictionary’s author Robert T. Caroll points out that the Moon only affects unrestrained waters, such as oceans. The water in our bodies isn’t even comparable.

Researchers Ivan Kelly (et al) noted that a mother holding her child “will exert 12 million times as much tidal force on her child as the Moon”. Seems odd? What about the Earth? It’s pulling on us all the time. What about the magnetic force of the Moon? Can that affect us? Very unlikely. The Moon’s magnetic force is so minimal that some modern textbooks don’t even acknowledge it has one.

Some of the available research has been criticized for methodological weakness. One such criticism of mental health studies is that “lunacy” has never truly been defined, so how can anyone possibly work with this term? A small number of studies are positive, which is statistically likely when an area is researched so frequently. However, these studies have also been criticized for poor method.

Does the Moon affect our behavior at all? In the most basic sense, the Moon probably affects mood in the same way looking at another attractive or eerie object would. Looking up at the Moon and finding it stunning or strange is, however, a far cry from the onset or worsening of mental illness! Seeing patterns in the Moon phases are likely to be more related to other cycles, such as weekly routines.

If someone becomes more aware of the Moon cycles, such as the belief it will make their work more difficult, they will notice the negative aspects of their work. They may also be on edge, leading to errors, but may not apply this same diligence to other times in the Moon’s phase. The Moon is a factor in this example, rather than a cause.

Sources

The Gravity of the Situation: The Moon and the Tides, Bad Astronomy, published by John Wiley and Sons, Inc. in 2002, author: Philip Plait

Full Moon and Lunar Effects, The Skeptic’s Dictionary website, accessed: 19th October 2008, author: Caroll, R.T