The belief that the moon influences human health and sickness has been a time tested one, lasting throughout many ages. There have been numerous accounts of a rise in violent crimes during full moons, in folklore and traditional medicine. In fact, a Mesopotamian tablet from 172 BCE, displayed at The Moon exhibition in 2019, was inscribed with description on how to ward off the evil effects of a lunar eclipse. In ancient Greece and Rome, girls were given crescent-shaped amulets on their birthday to protect them from evil spirits. Women also wore them to improve fertility and for protection during childbirth. 
The influence of the lunar cycle is especially profound in Hindu mythology and practice. A Sanskrit saying ‘Yat Pinde Tat Brahmande’, which translates to ‘Whatever is in this body is in the cosmos too’, holds great significance. Ancient cultures always believed in the inter-connectedness of beings and that everything affects everything else. This created room for reverence for the celestial bodies among many native cultures in the world. A fundamental connection that is drawn is that the moon influences the water element, and the way tides rise and fall. Our bodies are made up of 90% water, so it is not unlikely that the moon should have an influence on our bodies and mind as well. Quantum physics talks about how everything in the universe—stars, planets, galaxies, living beings—operates on a certain frequency. Similarly, the frequency of the moon also interacts with the frequency of our mind to create an impact on us, influencing both the conscious and subconscious mind. 
The moon’s impact on human health has been speculated through millennia. In ancient Roman philosophy, Pliny the Elder postulated that the moon could ‘penetrate all things’, influencing tides, marine life, plants, animals and human activity. While science has since explained some lunar phenomena, like tides and eclipses, much is still shrouded in mystery. Probably the most pervasive of all lunar legends is the moon’s ability to affect night-time behavior. There is no shortage of tales recounting nocturnal mayhem, sleep disturbances, and insomnia driven by the moon’s untold power. Does this hold true? Modern research methods have shed new light on the relationship between moon phases, sleep, mental health and diseases. 
Phases of the moon
The moon undergoes a transformation every month and this is due to the shape of the directly sunlit portion of the moon as viewed from earth. The lunar phases gradually change over a synodic month (about 29.53 days) as the Moon's orbital positions around Earth and Earth around the Sun shift. The visible side of the moon is sunlit to different extents, depending on the position of the Moon in its orbit. Thus, this face's sunlit portion can vary from 0% (at new moon) to 100% (at full moon). There are four main lunar phases: the new moon, first quarter, full moon, and last quarter (also known as third or final quarter), when the Moon's ecliptic longitude is at an angle to the Sun (as viewed from the center of the Earth) of 0°, 90°, 180°, and 270°, respectively. Each of these phases appears at slightly different times at different locations on Earth. Intermediate phases appear in the interval between the main phases and include crescent and gibbous. The description of ‘waxing’ is used for stage when the Moon's apparent shape is thickening, from new to a full moon, and ‘waning’ when the shape is thinning from full to new moon. 
The Lunar cycle effect on sleep
Although the sun is the primary source of light and synchronizer of circadian rhythms for most species, moonlight too, modulates nocturnal activities in many species. Moonlight is quite bright to the human eye and in the absence of any other source of light, it may have affected sleep and human nocturnal activity. But the actual effect it has on humans is still shrouded in controversy. Many studies contradict the effect of lunar cycle on sleep, but more recently, studies conducted in strictly controlled laboratory conditions have proven the effects of the lunar cycle on sleep. 
In the natural world, lunar impact on biological rhythms is well documented, for example, variations in tree diameter, reproductive patterns of crabs, spawning events in the Great Barrier Reef and night-time activity of monkeys. Human studies indicate there’s a disruption of sleep with the full moon. One sleep study analysis used several metrices and found that the full moon was associated with worse sleep. During this lunar phase, participants took five minutes longer to fall asleep, slept for 20 minutes less, took longer to reach REM sleep, experienced a 30% reduction in deep sleep, and reported reduced sleep quality. Another study discovered that sleep time was reduced by 25 minutes while arousals and awakenings increased during a full moon. One analysis reviewed data from 319 people who underwent a one-night sleep study. Those observed during a full moon had lower sleep efficiency, less deep sleep, and delayed time reaching REM sleep. One of the most extensive studies on this topic was conducted on three indigenous Argentinian communities and 464 American college students from major cities. Regardless of their location and amount of artificial light exposure, all groups slept later and for lesser time in the week preceding the full moon. 
Mechanisms by which the moon affects sleep
Most theories for sleep disruption during full moon, pin the amount of sunlight reflected back to earth as a causative agent. The body’s circadian rhythm is controlled by the rise and fall in hormones, which responds to light. Therefore, light levels are one of the most significant influences on sleep onset and quality. However, there are concerns about the moon’s luminance as the primary mechanism for sleep disruption. Moonlight brightness is only 7% the strength of sunlight, which is a relatively low intensity. People are frequently exposed to far more artificial light at night than the amount reflected by the moon. Furthermore, research studies on sleep disruption during the full moon were often conducted on cloudy nights or in closed, windowless environments. Hence this theory does not hold too much weightage. 
One theory gaining popularity is the moon’s ability to cause electromagnetic fluctuations on Earth. Earth’s electromagnetic field has a long tail or “magnetotail” shaped by solar winds. As the moon orbits Earth each month, it passes through the magnetotail during the full moon phase and becomes negatively charged. The moon’s magnetic charge can then influence Earth’s electromagnetic field through a sophisticated feedback process. Research suggests that humans maybe sensitive to these geomagnetic variations. Other events such as geomagnetic storms and the aurora borealis have also been connected to a range of health effects, such as headaches, blood pressure fluctuation and heart rate variability. The exact mechanism of action is not yet known, but can be attributed to hormone levels, DNA breaks and inflammation. 
The human body is made of mostly water, and it is natural for research to look at the gravitational pull of the moon to be able to affect human health, just as it affects ocean tides. But this theory hasn’t garnered much proof, mainly since the impact of the gravitational pull of the moon on a person is less than one-millionth of the size of an atom and cannot cause any significant impact. Also, the gravitational pull of the moon is roughly similar on full moon and new moon days, thus leading to dismissal of this theory. 
Effect on health and diseases
Some health conditions such as seizures, gout attacks, some heart conditions and gastrointestinal conditions are impacted by the lunar cycle. Polychronopoulos et al, analyzed the effects of the lunar phases on seizure occurrence in the emergency unit and found a significant increase in seizure occurrence on full moon days, while the rates were lower on all other days of the lunar cycle. This might be due to the direct effect of the moon on the patient or due to the impact of the patient’s behavior.
Daily occurrence of gout attacks has been found to peak at the new moon and full moon days of the synodic lunar cycle. Maximum attacks have occurred with the peaking of lunisolar tidal effect. Similar relation of attacks to synodic moon was seen in bronchial asthma of children, and a reciprocal one in paroxysmal tachyarrhythmia. The attack of atrial fibrillation in male subjects during a 14-year study is lowest in the full moon and a marked increase to peak shortly after the extreme southern position of the moon in the tropic cycle. A very recent study investigated that visual acuity was highest at the full moon and lowest at the new moon. Roman et al, compared the number of admissions of gastrointestinal hemorrhages on full moon and new moon days, across a 2 year period and found an increase in the admissions on full moon days. 
Effect on mental health
Circadian rhythms not only affect sleep, but they are also known to affect mental and physical health. With the increased use of artificial light sources, circadian rhythms are adapting to new sleep-wake cycles and further influence other conditions such as anxiety, depression, bipolar disorder and schizophrenia.  The belief that the lunar cycle is associated with the onset and severity of psychiatric symptoms has persisted since the Middle Ages. This belief still occurs in some mental health professionals, who report that the agitation of psychiatric symptoms induced by the full moon results in increased admissions, suicides, homicides, and emergency department (ED) visits. Opinion surveys conducted with ED personnel also indicate the belief that the demand for patient services increases during the full moon.
One study looked at a 3-day, 24-hours and 12-hours model of ED presentations and found no influence on the 3-day model. But with the 24-hours and 12-hours models, significant effect of the lunar cycle was observed, resulting in higher psychiatric ED presentations during the full moon. In the 24-hours period, it was also found that patients presenting with personality disorders had a more severe episode during full moon. 
Bipolar disorder is highly prone to the lunar cycle, and this has been established with proof. Specifically, on study examined 17 patients with bipolar disorder, which tended to switch from depression to mania very rapidly, during full moon days. This study found that the circadian pacemaker, which is a small group of nerves, become synchronized with the lunar cycle. This triggers changes in sleep which further triggers severe symptoms of bipolar disorder. 
Effects on human behavior
Lunar cycles have known to influence human behavior with increase in traffic accidents, crimes, suicides etc. In one study that compared daily records of traffic accidents over a year, it was observed that the number of traffic accidents in a one-year period, were higher on the two days leading to the full moon and lowest of full moon days. A computer-evaluated complex study conducted in Dade County, Florida, showed a clustering of homicides and aggravated assaults around the full moon days. This study further looked at sex differences in crime reporting and found an increase in calls from females and a decrease from males during the new-moon period, and there were proportionally more calls from males a fortnight later. 
Effects on menstruation and fertility
Women’s average menstrual cycle is 28 days, and the moon follows a 29+ day cycle too. As per some Chinese researchers, this may not be just a coincidence, as they discovered that about 30% of women enrolled in the study, ovulated during a full moon, and menstruated during the new moon. The cultural term for this is White Moon Cycle and is said to mimic the fertility of Earth, full moon being the most fertile.
Two studies conducted on a group of women with 28-to-29-day menstrual cycle found that most women menstruated around the new moon day and a reduced chance of menstruation was observed around full moon days. A study was conducted by Weigert et al. and they investigated the effect of the lunar cycle on in vitro fertilization. The study covered a period of 7 years and concluded a borderline increase in pregnancy rates during the perigee (closest to earth) cycle of the moon.
Perception of lunar cycle in Hindu mythology
Our physical body is said to have two types of energies as per Vedic literature — prana and mind or consciousness. In every organ of the body, there are two channels supplying energy. Lunar energy is said to enter the pineal gland and exercises control of all activities from night till the time we wake up. Performing meditative rituals during the full moon help in going inwards; transcend the mind and to help achieve full divinity within. The pineal gland, which is hormone controlled, reacts to the bioelectric signals of light and dark, and meditation activates this bioelectric energy.
Surprisingly, the lunar effects are limited to the human race. The body maintains a 28-day cycle of hormonal and physiological characteristics. The female menstrual cycle is a notable example. Our behavior, health and physiology run on the 28-day cycle of some kind. It is not coincidental that we have a particular relationship between various phases of moon and human biology. Certainly, there is a mystic connection between fertility, birth rate, reproductive factor, sexual behaviour and the lunar cycle.
Exploration and better research is the need of the hour to establish this phenomena that the lunar cycle exerts on humans. Further proof will help provide better healthcare and help individuals understand the impact of the moon and act, thereby.
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