A full moon may be to blame for sleepless nights after all.
Scientists at the University of Basel, Switzerland say they have found the first reliable evidence that sleep patterns are influenced by lunar changes. The study, published in Current Biology, shows brain activity related to deep sleep in volunteers dropped by 30 percent around the full moon. The study subjects also took longer to fall asleep and had shorter nights.
"It could be important," said Eric Chudler, executive director of the Center for Sensorimotor Neural Engineering at the University of Washington in Seattle. 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 to 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 an intermittent form of insanity believed to be related to the moon.
For generations, people around the world have passed down tales of werewolves and other moon-related curses.
Scientists have attempted over the years to discover a link between the satellite's impact and human behavior. These latest findings may provide a boost to the field.
Researchers at the Centre for Chronobiology at the Psychiatric Hospital of the University of Basel originally set out to examine 33 volunteers' circadian rhythms, which are physical, mental and behavioral changes that respond to light and darkness over a 24-hour cycle.
One evening at the pub several years later, the research team got talking about how the moon -- which was shining full that night -- could affect sleep. Christian Cajochen, head of the Centre for Chronobiology, said he came to realize several of the scientists believed there could be an impact. The team decided to go back over their study data, which included electroencephalograms of patients' non-rapid-eye-movement sleep and hormone secretions related to sleep, and match it up with a lunar calendar.
The results showed a steep drop in brain activity related to deep sleep. The volunteers, 33 of them divided in two age groups, took 5 minutes longer to fall asleep and their sleep duration was reduced by 20 minutes, according to the research. Their bodies also produced less melatonin, a hormone known to regulate sleep.
"I was very skeptical until we saw the data," said Cajochen, the lead researcher on the study. "We have to follow it up."
Cajochen said he didn't "dare publish it right away because the issue is very controversial. Until now there hasn't been a peer-reviewed study like this." Cajochen wants other researchers to confirm his team's findings. An ideal study would look at patients over the full lunar cycle, which is 29.5 days, he said.
Earlier studies have provided promising yet ultimately inconclusive glimpses of the moon's impact on humans and animals.
The British Medical Journal published two articles on dog bites and the full moon in its Dec. 23, 2000 edition. One showed the number of people bitten by animals "accelerated sharply" at the time of a full moon based on 1,621 patients seen in the emergency room at Bradford Royal Infirmary in Bradford, England, over a two-year period. The other, based on admission rates for dog bites over a one-year period at public hospitals in Australia, showed no moon impact.
Data on crime has been equally mixed. Based on police records and emergency room visits in Dade County, Florida, over a five-year period, researchers found a "significant clustering of cases" of homicides and aggravated assaults around the full moon, according to a study published in The Journal of Clinical Psychiatry in May 1978. Another study looking at police records of arrests in Decatur, Illinois, between 1967 and 1973 found no relationship between lunar activity and violence.
"The overwhelming evidence is negative," said Chudler of the University of Washington, a neuroscientist who has looked at 100 peer-reviewed papers on the lunar effect. "Most of them show no correlation but even if there is a correlation, it doesn't mean one causes the other."
That hasn't stopped police from drawing their own conclusions. In the seaside resort of Brighton, England, the police department decided in 2007 to put extra officers out on the streets during full moons after comparing crime data and lunar graphs and finding that violence waxed and waned along with the moon.
"From my experience, over 19 years of being a police officer, undoubtedly on full moons, we do seem to get people with, sort of, stranger behavior -- more fractious, argumentative," Andy Parr, an inspector with Sussex police, told the BBC.
Chudler's sister-in-law, a sheriff in the Seattle area, is a staunch believer in the lunar effect, he said.
"Of course when you talk to the bartender or the police officer or the nurse they'll say there's an effect," he said.