Are Children Like Werewolves? Science Investigates!

Well hello hello! Welcome to “This Week In Parenting Research”, an (allegedly) biweekly column where I take a look at research that might be of interest to parents.  This week I came across a paper with the excellent title “Are Children Like Werewolves? Full Moon and Its Association with Sleep and Activity Behaviors in an International Sample of Children”, and I knew I had to check it out.

Nearly everyone I know who works the public regularly (teachers, nurses, social workers, DMV workers, etc) has made the joke at one point or another “everyone was acting up today….must be the full moon!”.  Now any good skeptic knows that these statements have very little credibility….many studies have been done and very little correlation has been found between moon phases and behavior. However, there has been some research that suggested that moon phases might effect sleep, either the quantity or quality. Other research however has failed to replicate these findings. The prior studies were done in adults, so the authors of this study wanted to specifically look at a large group of children from multiple countries to see if they could find a correlation between lunar phase and sleep.

What did they do?

5,812 children (all around age 10) from 12 different countries were recruited as part of the International Study of Childhood Obesity, Lifestyle and the Environment (ISCOLE). This is a pre-existing group that recruits from economically/developmentally/ethnically diverse countries, and allows researchers to compare children that are much more representative of the world as a whole than most studies. The had the children wear physical activity trackers (from this company, similar to this one) for at least 7 days. This measured both their daytime physical activity and sleep patterns.

How’d they analyze this?

Overall the researchers got over 33,000 days of recorded activity from the kids over 28 months. They then compared the amount of physical activity and sleep kids got while the moon was in each phase (full moon, half moon, new moon). It’s worth noting that this was a cross sectional study….kids were not compared to themselves in different phases of the lunar cycle, they were compared to other kids whose data was collected in a different part of the lunar cycle. They controlled for age, sex, parental education level, BMI and day of the week.

What did they find?

Overall, they found that the full moon led to kids getting about 5 minutes less of sleep when there was a full moon as opposed to a new moon. This is one of those results that known as “statistically significant, but not clinically significant”. A large sample size like this one makes it easy to get a low p-value, but the authors do not feel the finding has a lot of practical use. It’s 5 minutes.

Interestingly, they actually reran the calculations a few times with different definitions of the moon phases (like using a full moon on only the exact night it’s full) and got the same findings.


The authors have no idea why sleep duration would shorten by 5 minutes during the full moon, but they suspect it might be increased light in the room. They were not sure that a 5 minute difference was particularly worth correcting even if it was real, but they did note that it might be worth investigating if there was a stronger effect on a sub-population (like those with physical illnesses) that might be hidden by the large sample size.

Sadly, they avoided stating definitively that your child is NOT a werewolf. I’ll leave you to draw your own conclusions on that one.

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Bethany is a perpetual student who just won't stop taking classes. She's gone from engineering to psych and family systems to applied statistics, and is really fascinated by how people feel about numbers. She blogs about this over at Graph Paper Diaries, and experimenting with contingency tables at Two Ways to Be Wrong.

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