Scientists have been arguing for a long time over how much truth there is in the old beliefs about the full moon and the effect, if any, it has on people. One of the most widespread beliefs is that a full moon disturbs sleep – in everyone, not just babies – and in fact recent research seems to prove that this belief has some foundation. In 2000 a group of 33 volunteers were monitored while sleeping in a special lab, but in fact they were not being tested for their reactions to moonlight. It was actually a study of general sleep patterns, and only years later did the researchers look at the data to see if the moon phases were affecting these at all (that’s way the findings were published so late). The overall results did point to a disturbing effect from the full moon, and in particular to a lack of deep sleep. It is interesting that this happened even when the volunteers couldn’t actually see the moonlight.
A lot has been written about this study, and it has even been suggested that we may be disturbed by the full moon for evolutionary reasons – more predators are active when there is a lot of light at night, so we may have evolved to be wary when it is very light outside at night (this could explain the origin of werewolf stories and similar folk tales).
However, a study of only about 30 people really isn’t enough to prove anything, besides even in this study the differences observed were very small. Many other studies have shown no effect, and where there is an effect you can often put it down to the fact that bright light does disturb sleep anyway. Studies of this kind do have to be very large and conducted over a long period in order to get at the facts, because there are so many factors that can influence the results. These can include weather, time of year, the subject’s mental and physical state and many others – and the strongest influence of all is the phenomenon known as confirmation bias. This is the tendency we all have to notice only the ‘evidence’ that seems to confirm the beliefs we have already. Thus even a trained scientist, for example, who believes that the full moon does influence behaviour, may unconsciously note and give weight to data that seems to prove this, and pay less attention to anything that doesn’t prove it. This is something everyone has, and the only real way to guard against it is to do studies so large that confirmation bias is overcome.
So, what is true for humans in general is of course true for babies as well, but with some important differences. For example, babies of course have different sleep patterns to adults anyway, so it makes sense that phenomena like moonlight could affect their patterns in different ways. Also, mothers and other carers take a lot of notice of their babies’ sleep habits, in a way that is unlikely to happen at any other time of life – so you might expect mums to notice any changes in these habits. And indeed if you go on a lot of mother and child websites you will find a discussion about this very topic, but not a lot of agreement. All that can be said with certainty at present, as there hasn’t been a study looking specifically at babies, is that the evidence of a full moon’s disturbing sleep (more than any other bright light; the gravitational effects can be discounted anyway) is inconclusive; but that future studies may yet reveal more.