Dr. David Mandell of the Children's Hospital in Pittsburgh and some colleagues studied existing data on health-care myths and did a 2005 study of area nurses. He said he found that 69 percent of surgical nurses in his study believed that a full moon led to more chaos and incoming patients that night.
"It is unbelievable how many nurses in southwest Pennsylvania believed in the superstitions," he told ABC News. But he said that it's simply part of the culture of medicine.
"In any high-stress, fast-paced field like medicine, superstitions run rampant when you feel a loss of control. This is especially true of emergency environments [because] you never know what will walk in. You need some way to explain the unpredictability of your environment," he said. "It passes on from senior to junior people in hospitals -- like old times telling it to new residents coming in."
Western Kentucky's Brady said that phenomenon isn't confined to just hospitals.
"You'll find that these beliefs that cluster around the moon, they are also relevant to parts of human behavior that are unpredictable," she said. "It's a way of imposing a categorical order on something that otherwise feels frighteningly out of control."
Some people consult the lunar calendar when deciding when to have surgery, she said. Each part of the zodiac corresponds with a part of the body (for example, legs and ankles are linked to Aquarius, sexual organs to Scorpio). And, as the moon moves through the different signs, the superstitious caution against medical intervention on that body part or region.
For farmers whose livelihoods depend on the health of their crops, planting by the phases of the moon is still common in some rural areas, she said.
The Farmers' Almanac, for example, advises planting crops that are valuable because of the parts that grow above ground (such as corn and wheat) while the moon is waxing, so that the moon pulls the plant out of the ground while it grows bigger.
Conversely, it advises planting root crops (such as turnips and yams) while the moon is waning so that the diminishing moon helps the vegetables grow deep into the ground.
She's also seen scientifically-trained physicians refuse to castrate livestock during certain phases of the moon because they think they'll bleed out. They've never seen documentation or evidence supporting that notion, she said, but cite anecdotes from their uncles or older family members.
Risks run high in matters of health and agriculture, and moon myths ease the fear.
"There's a comfort factor that accompanies authority that extends back in time," she said. "If your feeling is that you are exerting a level of control and authority, that can reduce an element of anxiety."
ABC News' Liam Berkowitz, Chris Francescani and Brittany Bacon contributed to this report.