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What effects can the full moon have on weather, people and animals?

By By Kevin Byrne, Staff Writer
July 23, 2016, 10:44:49 AM EDT

More than 200,000 miles away from Earth, the moon shines brightly through the darkness of space. But what impact, if any, does it have in regards to life on Earth?

While the subject of the full moon and its possible effects on human behavior and nature have long been theorized, finding hard scientific evidence remains a challenge.

Inclement weather, high tides cause unsettled marine environments

One certainty in regards to the moon’s impact is that its gravitational pull will affect ocean tides.

The moon does not have a perfectly circular orbit around the Earth, meaning that when it is closest to the Earth, it is at “perigee” (225,623 miles) or at “apogee” (252,088 miles) when it is farthest away, according to NASA.

When the moon is closer to the Earth and is full, or new, that’s when it has its biggest impact and when that occurs, spring tides are created, according to Expert Senior Meteorologist Dan Kottlowski.

Spring tides have no relation to the season spring, but rather, the term indicates the concept of the tide “springing forth,” according to the National Oceanic and Atmospheric Administration.

High tides can be significantly higher than normal during this time.

A full moon will not directly affect the weather, but when the tides and weather are working hand in hand, the situation can be exacerbated and cause problems on shore.

“If you have winds [that] are blowing the water on to the coast, then those are the situations which bring us the worst marine environment,” Kottlowski said. Such conditions include coastal flooding and higher than normal surf, he added.

“It depends on when the highest tides are occurring, so you can get a higher-than-normal water levels caused by, again, the wind hitting the coast in a certain direction,” Kottlowski said. “If the winds are offshore, they’re not going to cause any problems at all.”

Occasionally tidal forces might influence the intensity of storm systems, and there have been some correlations between storms occurring and being stronger during a full or new moon, according to Kottlowski. However, he emphasized there is no hard science to prove this conclusively.

Pets may be at higher risk for injuries


On busy nights throughout her career in emergency veterinary medicine, Dr. Raegan Wells would often hear staff members and colleagues wonder aloud, “It must be a full moon tonight.”

Wells, currently the chief medical officer at Emergency Animal Clinic in Phoenix, was skeptical of the notion that they were busier during a full moon, so she decided to take matters into her own hands to see if there was a correlation.

In 2007, Wells co-authored a retrospective study at Colorado State University that examined whether the volume of animal emergency room visits increased on the days of the full moon. The data was compiled of nearly 12,000 case histories of small animals, specifically dogs and cats, from 1992-2002 at the university’s veterinary medical center. Such emergency types include animal bites, epilepsy and trauma to name just a few.

The results of the study were surprising, she said.

While the specific day of the full moon did not see a higher caseload, Wells said the days surrounding a full moon, which they would call ”fuller moon days,” when the moon is in its waxing gibbous, full or waning gibbous state, were more pronounced.

Specifically, data indicated that the "risk of emergencies on fuller moon days was 23 percent greater in cats and 28 percent greater in dogs when compared with other days," according to a school news release.

Data from the study did not provide conclusive results for the increased number in visits although Wells did suggest one possibility.

On full moon nights, due to increased luminosity, some animals may stay out longer and remain more active, thus being more likely to be traumatized or injured, Wells and fellow researchers theorized.

However, due to the study being performed in Fort Collins, Colorado, where there was lots of artificial light due to its urban setting, it was harder to assume moonlight was a factor, Wells said.

One of the challenges of the study, Wells pointed out, was that there was an inherent limitation because some things you can’t control in a retrospective study.

The potential influence of owner behavior cannot be discounted, she said. All of the animals treated, including strays, were brought in by a human who was concerned for the animal’s well-being.

“I think that’s interesting, I don’t know that we could control for that in this study design,” Wells said. “But perhaps that played a role as well, you know, maybe the owners were a little bit more aware of what was going on with their pets on fuller moon days.”

In the years since the study was released, Wells said there have been no additional follow-ups or rebuttals on this topic. However, the sentiment still exists, and she often hears, even from friends in human medicine, comments about higher case loads on nights with a full moon.

“Despite this paper really showing that full moon days were no busier, there’s still definitely that perception,” Wells said.

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Human sleep patterns may be affected during a full moon


The annals of human history are filled with interesting lunar theories and studies about the effect of the full moon and human physiology and behavior.

From general lunacy and medical issues to whether crime rates varied, researchers have tackled a bevy of topics to find out if behavior can change during this phase of the moon.

In the last two years, several studies have been published with mixed conclusions about whether sleep cycles are impacted by the moon.

In 2013, researchers from the University of Basel in Switzerland found that restful sleep decreased on the day of the full moon and its surrounding days, Scientific American reported.

Specific findings in the study discovered a 20-minute shorter sleep duration, a five-minute longer time to fall asleep and a 30-percent decrease in deep sleep. The researchers examined the sleep cycles of 33 volunteers, half of whom were between the ages of 20-31 years old, with the other group in the age range of 57-74.

"This is the first reliable evidence that a lunar rhythm can modulate sleep structure in humans when measured under the highly controlled conditions of a circadian laboratory study protocol without time cues," the researchers said.

The study was initially done to examine the circadian aspects of human sleep, and it wasn’t until several years later that the study was refocused to examine the potential influence of the lunar phase on sleep.

Last summer, a group from the University of Gothenburg in Sweden released a separate study, and they found similar results to the Swiss research team, including a 20-minute decrease in sleep while studying 47 volunteers. Unlike the Swiss-based study, a greater impact on REM sleep was noted during the new moon, according to Michael Smith, one of the authors of the report.

However, scientists from the Max Planck Institute of Psychiatry in Munich, Germany, studied sleep patterns of a much larger group, 1,200 volunteers over the course of 2,000 nights and found no such correlation.

“Investigating this large cohort of test persons and sleep nights, we were unable to replicate previous findings,” Dr. Martin Dresler, a neuroscientist at the institute said.

"We could not observe a statistical relevant correlation between human sleep and the lunar phases."

Both Smith and Dresler stated that more studies are needed to determine a definite answer.

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