Maybe you can blame a full moon for sleepless nights after all.
Scientists at the University of Basel, Switzerland, say they have found the first reliable evidence that sleep patterns are correlated with lunar changes.
Their study, published in Current Biology, found that deep sleep, as measured by brain activity, dropped by 30 percent around the full moon. The study's volunteers also took longer to fall asleep and had shorter nights under the full moon.
“It could be important,” said Eric Chudler, executive director of the Center for Sensorimotor Neural Engineering at the University of Washington in Seattle. He noted though, that the Swiss researchers aren't “saying the moon controls the person's sleep pattern. They're saying the body has an internal clock that's similar to the lunar cycle. It's different from the traditional myth.”
The full moon has been blamed for murder and mayhem since ancient times.
The term lunacy was coined in the 16th century to refer to a form of insanity believed to be related to the moon. And for generations, people around the world have passed down tales of werewolves and other moon-related curses.
Scientists have tried over the years, with little success, to discover a link between the moon and human behavior. The latest findings might help.
Originally, the Swiss researchers at the University of Basel's Center for Chronobiology set out to examine circadian rhythms, which are daily physical, mental and behavioral changes that respond to light and darkness.
Later, the research team began talking about how the moon might affect sleep. They decided to go back over their data and compare it with a lunar calendar.
The results showed a steep drop in brain activity related to deep sleep around the time of the full moon. The 33 volunteers took 5 minutes longer to fall asleep, on average, and their sleep duration was reduced by 20 minutes. Their bodies also produced less melatonin, a hormone known to regulate sleep.
“I was very skeptical until we saw the data,” said Christian Cajochen, lead researcher. “We have to follow it up.”
Past studies of the moon and behavior yielded provocative but inconclusive hints:
» The British Medical Journal published studies in 2000 about dog bites and the full moon, for example. One found the number of people bitten by animals “accelerated sharply” at the time of a full moon, but the other found no full-moon impact on dog bites.
» Similarly, a 1978 study of Dade County, Florida, crime records found a “significant clustering of cases” of homicides and aggravated assaults around the full moon. But a study in Decatur, Ill., covering 1967 to 1973 found no such link between lunar activity and violence.
“The overwhelming evidence is negative,” said Chudler, the University of Washington neuroscientist. He has examined 100 peer-reviewed papers on the lunar effect. “Most of them show no correlation. Even if there is a correlation, it doesn't mean one causes the other.”
Still, lack of hard evidence hasn't stopped police departments from acting.
In the British resort of Brighton, for instance, police decided a few years ago to put extra officers on the streets during full moons, after comparing crime data and lunar graphs and finding that violence waxed and waned along with the moon.
In the U.S., Chudler said his own sister-in-law, a sheriff in the Seattle area, is a staunch believer in the lunar effect.