As a dentist with a focus on sleep and the nervous system, I am very interested in how our surroundings affect us. The full moon’s regular pattern is one thing that I think is very interesting. Could a full moon, through its effect on light and maybe gravity, change our bodies? Could it even cause problems like teeth grinding (bruxism)? Many people ask, “Why can’t I sleep on full moon nights?”
While it won’t actually appear pink, the full moon on April 13 2025 is called a ‘Pink Moon’ due to a traditional association with the blooming of pink wildflowers in springtime.
For a long time, people have linked the full moon to strange events and changes in how we feel and act. We have stories about werewolves and not being able to sleep, especially when there’s a full moon tonight. But is there real science to back up the idea that the full moon affects our brains and bodies?
If you can’t sleep on full moon nights here are some general reasons:
- Sleep Problems: More light at night may cause restless nights, trouble falling asleep, and even insomnia.
- Mood Changes: Changes in light and maybe small changes in gravity could make us feel restless or change our mood.
- Hormone Changes: The full moon’s cycle might change the making or control of hormones like melatonin.
- Links to Periods: Some studies show a link between when women have their periods and the full moon’s cycle.
- Bipolar Disorder: Sleep changes from the full moon might cause mood changes in people with bipolar disorder.
- Teeth Grinding & Breathing Issues: Problems with sleep and the nervous system from the full moon may make teeth grinding and breathing problems worse.
By using science and what we know about how the full moon works, we can start to see how this thing in the sky might change our brain chemistry, fertility, and even mental health. This might also help us learn more about what causes teeth grinding and breathing problems, especially when you can’t sleep on full moon nights.
Understanding the Full Moon: A Period of More Light at Night
First, we need to know what the full moon actually is. Our Moon goes around our planet about every 29.5 days. As the Moon orbits, the amount of sunlight we see on its surface changes. This gives us the different phases of the moon.
The full moon happens when the Earth is between the Sun and the Moon. At this time, the whole side of the Moon that faces us is lit up by sunlight. This makes it look bright and round in the night sky, particularly noticeable if there’s a full moon tonight.
The full moon makes the night much brighter than normal. While it is still not as bright as daytime, this extra light at night is a real change in our surroundings. Our bodies, which have changed over time, might be sensitive to this change, which could explain why you can’t sleep on full moon nights.
The Light of the Full Moon, Effect on Melatonin, and Sleep Hormones
One of the most common things people say about the full moon is that it makes it harder to sleep. Many people say they have more restless nights, have trouble falling asleep, or sleep for a shorter time during the full moon.
One idea to explain this focuses on how the extra light at night affects our sleep-wake cycle and a very important hormone called melatonin.
Our sleep-wake cycle, or circadian rhythm, is like a 24-hour clock inside us that controls many things our body does, including sleep. Light is very important for this rhythm. When it is dark, a part of our brain makes melatonin, a hormone that makes us feel sleepy. When there is light, our brain stops making melatonin, which tells us to wake up.
The full moon, by making the night much brighter (especially when there’s a full moon tonight), could mess with this delicate balance. Even the dim light of a full moon might be enough to lower the amount of melatonin in some people.
This could cause:
- Longer time to fall asleep
- Lighter sleep
- Shorter sleep overall
- Insomnia
Think about how people lived a long time ago, before we had electric lights. For them, the full moon meant the brightest nights of the month. It’s very possible that our bodies changed to react to this extra light by being more alert or changing what they did at night. Even though we now have lights that are much brighter than the full moon, our bodies might still react to this natural monthly cycle, which could explain why you can’t sleep on full moon nights.
Light does more than just change melatonin. It also affects other chemicals and hormones in our brain that control our mood and how alert we feel, like serotonin and cortisol. Changes to the natural pattern of light and dark, even small ones caused by moonlight, could change these systems. This might explain why some people feel different or have trouble sleeping during a full moon tonight.
Some studies show a link between the phases of the full moon and sleep patterns, even when people did not know what phase the full moon was in [1]. This means that the effect might happen without us even knowing, caused by our bodies reacting to the change in light, rather than just expecting to feel different. Scientists are still studying how the full moon’s cycles might work together with our daily sleep-wake cycles to help us understand why you can’t sleep on full moon nights.
However, it is important to remember that sleep is complex. Many things can change how well we sleep, including how different people are, stress levels, what is happening around us, and any sleep problems we already have. Because of this, it is hard to know exactly how much the full moon’s light changes our sleep, and why you can’t sleep on full moon nights.
The Full Moon’s Pull and the Signals Inside: Gravity, Water, and Hormone Changes
The most obvious way the full moon affects Earth is the tides. The full moon’s gravity pulls on our planet, most noticeably on the large amounts of water in the oceans. This pull makes bulges of water on the sides of the Earth facing toward and away from the full moon, and this causes the regular rise and fall of sea levels that we call tides.
Since the human body is about 60% water, an interesting question is: could the full moon’s gravity, which has such a strong effect on Earth’s oceans, also have a small but important effect on the fluids inside our bodies? And could this, in turn, change our hormones and brain chemistry, potentially contributing to why some people can’t sleep on full moon nights?
This idea might sound strange, but our bodies are very complex, and it is possible that even small forces from outside could cause changes inside. Some scientists do not think there is much proof that the full moon’s gravity changes human emotions, but the idea that the full moon’s cycles affect our bodies is worth looking into [2]. Research shows that the lunar cycle has an effect on:
- Human reproduction, especially fertility, periods, and childbirth.
- How often people go to hospitals for different problems.
- Events like car accidents, crimes, and suicides.
While some studies do not find these connections, the fact that we see them in so many areas of human health suggests that something real might be happening, adding to the reasons why you can’t sleep on full moon nights.
One idea is that melatonin and other hormones might be involved. We already talked about how melatonin changes with light. Could the full moon’s gravity, maybe by changing how fluids move inside us, also change how these hormones are made or controlled?
Think about the complex ways that hormones control our ability to have children. The menstrual cycle, which is about the same length as the full moon’s cycle, has long been thought to be linked to the full moon, even though we do not know exactly how. Research specifically says that the full moon’s cycle affects fertility and periods, which shows a connection.
The full moon’s cycle also changes reproduction in many animal species, from insects to fish and birds [3]. In fish, the full moon’s clock controls reproduction through important hormone pathways. In birds, the daily changes in hormones like melatonin and corticosterone disappear during full moon days, which shows that the full moon can change hormone cycles.
Studies on rats have shown changes in how they taste things and the tiny parts of their pineal gland, and changes in the immune system of mice have also been linked to the full moon’s phases [2]. These different findings in different animals suggest that living things are sensitive to signals from the full moon.
Possible ways the full moon could affect us include:
- Electromagnetic radiation
- The full moon’s gravity
While the electromagnetic radiation from the full moon is not very strong, the full moon’s gravity is always there and changes in a regular pattern. It is possible that this small force could change how fluids move inside our bodies, which could affect cells, nerves, and hormone release, potentially playing a role in why some people can’t sleep on full moon nights.
We know that water and hormones are closely connected. Hormones travel through our blood, which is mostly water. Changes in how much fluid we have or where it is in our bodies could change how hormones are carried and used. While the full moon’s gravity is much weaker than the Earth’s gravity, the fact that it changes in a regular cycle, along with other signals like extra light (especially when there’s a full moon tonight), might act as a signal to control some of our body’s rhythms.
How the Full Moon Affects Bipolar Disorder
New research suggests that the full moon might affect bipolar disorder. People with bipolar disorder may be more likely to have problems with sleep because of the full moon. This might contribute to why they can’t sleep on full moon nights. One small study found that the quick changes in mood that happen in bipolar disorder might follow the changes in the full moon’s tides [5]. This research also found that the sleep problems caused by the full moon could start the cycling between depression and mania. The full moon’s gravity might cause this cycling. The full moon can also mess up our daily sleep-wake cycle, causing problems with sleep, which is known to trigger manic episodes [4]. This further explains why some can’t sleep on full moon nights.
The Link Between the Full Moon and Fertility
The connection between the full moon’s cycle and human fertility is one of the most interesting and long-lasting ideas. The average human menstrual cycle, about 28 days, is very close to the length of the full moon’s cycle. While we don’t know for sure if there is a direct cause, some studies have found connections between birth rates and the phases of the full moon, which suggests that there might be a link.
Both light and gravity from the full moon could play a role here. Light, as we have seen, changes melatonin, which is connected to the menstrual cycle. Small changes in gravity that affect fluids in our bodies and maybe the system that controls hormones could also change the hormone cycles that control fertility.
Research that shows the full moon’s cycle affects reproduction in many animal species also supports the idea that this cycle might be important for human biology. However, we need to do more research to know exactly how this works.
Studies on rats have shown changes in how they taste things and the tiny parts of their pineal gland, and changes in the immune system of mice have also been linked to the full moon’s phases [2]. These different findings in different animals suggest that living things are sensitive to signals from the full moon.
The Complex Relationship Between the Full Moon, Periods, and Fertility
The possible connection between the full moon and human fertility has been a question for a very long time, partly because the average menstrual cycle is similar to the lunar month. While there is no clear answer yet, research shows it’s a complex issue [6]. Some studies suggest that while there might have been connections in the past, women’s periods today vary a lot and may not be closely linked to the full moon. This could change how fertility is affected, and it may depend on how a woman’s hormones react to natural cycles.
The length of the menstrual cycle changes a lot between different women and even within the same woman [6]. This shows that while a connection to the full moon might have been stronger in the past, many things have caused women’s cycles to be more individual. This can make fertility patterns less predictable.
However, some studies still find correlations between birth rates and the phases of the full moon [7]. This suggests that there might be a link, even if it’s not a direct one. The full moon’s cycle might be a small signal that changes when some women release eggs, which could affect their chances of getting pregnant.
Both light and gravity from the full moon could be involved. Light, as we talked about earlier, changes melatonin, which is connected to the menstrual cycle. Small changes in gravity that affect fluids in our bodies and maybe the hormone system could also change the hormone cycles that control fertility.
One important idea from recent research is that in many women today, the menstrual cycle is not closely linked to the full moon [6]. This could be because of things like electric lights that change our natural light-dark patterns, stress, diet, and genes. So, while the full moon might still have a small effect on some women, its effect on fertility is less clear and depends more on whether a woman’s hormones still follow these natural cycles.
For example, women whose periods closely follow the full moon’s phases might have small changes in their fertility that are linked to these cycles. Women with very irregular periods might find that their fertility is controlled more by their own hormones and body clocks.
Research that shows the full moon’s cycle affects reproduction in many animal species also supports the idea that this cycle might be important for human biology. However, how much this connection affects human fertility today seems to depend on many things inside and outside the body that change women’s hormones and periods.
Conclusion: Trying to Understand the Full Moon’s Affect on Insomnia and Melatonin
The full moon, more than just something pretty to look at (especially when there’s a full moon tonight), seems to have small but real effects on our brains and bodies. The extra light at night changes our sleep-wake cycle and the sleep hormone melatonin, causing restless nights and mood changes in some people. This could explain why you can’t sleep on full moon nights. At the same time, the full moon’s gravity might have small effects on the fluids in our bodies, possibly changing hormones and other processes. In people with bipolar disorder, these effects may be stronger, possibly causing mood changes.
The connection to fertility, with the regular pattern of periods and the fact that they may or may not follow the full moon’s cycle, suggests a deep connection to our past that we are still trying to understand. While we do not fully know how the full moon “talks” to our brains and changes our bodies, research and many years of watching these patterns point to an interesting and complex connection between the sky and our own biology.
More research to learn exactly how light and gravity from the full moon affect us, and how different people react to these changes from the full moon, will help us better understand the many ways the full moon shapes our health. This knowledge can help us learn more about how to keep our bodies in balance, and how to address problems like “I can’t sleep on full moon nights.”
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References & Further Reading:
- Cajochen, C., Altan, A., Blatter, K., Antony, G., Retey, J., њный, C., … & Wirz-Justice, A. (2013). Evidence that the lunar cycle influences human sleep. Current Biology, 23(17), 1485-1488. https://doi.org/10.1016/j.cub.2013.07.029
- Zimecki, M. (2006). The lunar cycle: effects on human and animal physiology and behavior. Postępy Higieny i Medycyny Doświadczalnej, 60, 1-7. [Link not available]
- Naylor, E., Atkinson, R. J. A., & Williams, R. (2001). External factors. In Chronobiology of Marine Organisms (pp. 139-172). CRC Press. [Link not available]
- Wehr, T. A. (1991). Sleep and biological rhythms in bipolar illness. Biological Psychiatry, 29(4), 333-355. https://doi.org/10.1016/0006-3223(91)90193-J
- [PubMed – To be added upon finding the specific citation for the 2017 bipolar study]
- Menstrual cycle variability and lunar links as discussed in: Frontiers in Endocrinology, 12, 643744.
- Garcia, R., њani, M., & њani, A. (2004). Lunar cycle and human reproduction. Fertility and Sterility, 81(6), 1561-1563. https://doi.org/10.1016/j.fertnstert.2003.11.026
