For millennia the Moon has held a certain fascination for humanity - we've turned to it as an emblem of prayer and worship, a destination worthy of repeated exploration, and a subject of scientific study. Of particular interest is the question of how the phases of the Moon itself affect human life and behavior.
Werewolves, or humans with the ability to morph into wolves, populate our literature, with the transformation usually occurring under a full moon. Even the word “lunacy” has roots around such superstitions, its use as part of the English language is first cited as early as the fourth century when people would attribute unusual behavior to the changing Moon.
Moonlight, or lack thereof as the Moon moves through all of its phases, may have some influence, though modern exposure to artificial light at nearly all hours of the day complicates this theory. Studies have suggested that people do tend to sleep less when the Moon is full, but the exact mechanism as to why is uncertain.
The gravitational pull of the Moon is known to influence ocean tides - and as the human body is composed of about 60% water, it stands to reason that the influence may extend to affect us in some way as well. The question is - just how much?
Do Moon phases affect mood?
It certainly seems like it, for some people, at least.
A peer-reviewed study of 17 patients with rapid-cycling bipolar disorder, meaning they alternate between manic and depressive states more quickly than those with traditional bipolar disorder, showed that the patients experienced mood shifts with a pattern of regularity to a degree unanticipated by Thomas Wehr, the author of the study.
Wehr hypothesized that the influence of the lunar cycle on human behavior patterns is much more of an individual phenomenon than something that can be witnessed throughout the population as a whole. He tracked his patients’ moods and episodes for months and discovered that their shifts usually occurred at a particular point during one of two cycles - the 14.8 day spring-neap tidal cycle, or the 13.7 day “declination cycle” between the Moon and Earth’s equator.
He also noted significant mood swings within his patients tended to coincide with “Supermoons,” which occur every 206 days when the Moon is both full and its orbit closest to earth, such as during the Super Flower Blood Moon in May 2021.
His theory, based on his findings, is not that the Moon itself causes swings in a person’s mood, but that the subtle environmental changes that come as a result may exert some influence over an unknown biological mechanism.
Does the Moon affect human sleep?
From what we know so far, there does appear to be some connection between our quality of sleep and where the Moon is in the sky. Some studies have suggested that the phases of the Moon have an influence over our production of the hormone melatonin, which is responsible for sleep-wake cycles.
One peer-reviewed study done in Switzerland examined the sleep quality of participants in laboratory conditions including complete darkness. Researchers measured brain activity and certain hormone levels over a period of 3.5 days. The phases of the Moon were not taken into account until years later when the researchers had the idea to cross reference their findings with the Moon’s phases at the time and discovered that participants took 5 minutes longer to fall asleep and slept a total of 20 minutes less on average around the time of the full Moon. They also experienced a notable drop in melatonin levels. As to why, we still don't know.
Another peer-reviewed study of over 300 participants revealed that “sleep efficiency” was reduced during the full Moon compared to how participants slept during other Moon phases. On average they stayed awake or remained in states of light sleep for longer when the Moon was full even in rooms without windows.
How does the Moon affect our lives?
That depends on what we consider an effect. It’s pretty well established that the Moon has some influence over the quality of sleep we receive, which can certainly bleed into other areas of daily life. Those who follow the Jewish or Islamic calendars lead lives greatly affected by the Moon, as each consists of 12 lunar months that dictate when rituals, holidays, and other life events will occur. But one peer-reviewed study showed that the Moon may affect us before our lives on earth even truly begin.
The study, published in the Nepal Medical College journal, showed that the influence of the Moon’s phases may extend as far as to influence a baby’s sex.
In the study of expecting Indian couples, those who ovulated and conceived at the full Moon gave birth to 42 male and 2 female babies, whereas the 40 women who “conceived on the day of ovulation 3 days prior to full Moon gave birth [to] 13 male and 27 female babies.” The study also mentions that all of the 5 women who conceived during the new Moon gave birth to female babies.
The researchers hypothesize that the variance in birth rates may have been due to changes in the mother’s vaginal pH and body temperature, but still haven’t determined exactly if or how the Moon’s phases influence these elements of biology.
Does the Moon affect mental health?
Perhaps - but we’re not quite sure yet. Some studies have suggested that there may be a correlation between mental health and the full Moon, but others can’t seem to find a link. If the state of a person’s mental health is affected by the Moon, it’s quite possible that this may be due to more indirect factors, such as decreased quality of sleep.
A peer-reviewed Finnish study of suicide victims compiled data from over 20 years to examine whether the lunar phases had any correlation with suicide rates. While no correlation was determined between the lunar calendar and male victims, a slight statistical significance was found within premenopausal women under the age of 45. Another peer-reviewed study by Italian researchers divided the Moon calendar into four main phases and tracked community-based contact with psychiatric services over a 10-year period, but they found no significant increase in the frequency of contact at any point during the four phases. So what does all of this mean? More research is needed, but it seems like there are biological mechanisms at play that are definitely worth a deeper look. We do know one thing - it certainly won't turn you into a wolf.