The Truth Behind "Can't Sleep During a Full Moon" — A Neurologist Explores the Science of "The Moon and Sleep": The Mechanism of Small Sleep Changes Occurring Before a Full Moon

"Can't Sleep on a Full Moon Night." The "Moonlit Night Legend," passed down in emergency and police settings, was reignited during the supermoon in the fall of 2025. So, what does science say? Based on an article by a neurologist and sleep specialist from the University of Pittsburgh, we organize the "truth" by combining the latest research and social media reactions.Medical Express

Spoiler: The impact is "not zero, but small"

Several studies indicate that in the days leading up to a full moon (when moonlight is strongest in the evening to early night), bedtimes tend to be later, total sleep time is reduced by about 15 to 30 minutes, and deep sleep slightly decreases. The main factor is "light." Nighttime light delays the internal clock, suppresses melatonin secretion, and shifts the brain towards wakefulness. The impact is more pronounced in environments with less artificial lighting, while it remains smaller in urban areas.Medical Express

This pattern of "delayed and shortened sleep before a full moon" has been observed in both urban and rural areas and across multiple cultures (suggesting the possibility that human sleep loosely synchronizes with the 29.5-day lunar cycle). A representative study is the 2021 Science Advances paper showing synchronization between lunar phases and sleep.Science.org

Gender Differences? — Suggestion that "men are more prone to disruption"

A large-scale polygraph study from Uppsala University in Sweden reported a decrease in sleep efficiency and an increase in mid-sleep awakenings in men during the "waxing crescent to full moon" phase. The impact on women was smaller (causality is not confirmed in observational studies).ScienceDirect

Relationship with Mental Health — "Sleep deprivation," not the "moon," is the mediator

It is established that sleep deprivation increases the risk of anxiety, depression, bipolar disorder relapse, and exacerbation of schizophrenia. Experts suggest that the "slight sleep deficit" before a full moon could be amplified in vulnerable individuals. However, evidence consistently linking lunar phases with changes in psychiatric emergencies or hospital admissions and discharges is weak—only small local differences are suggested in some studies from India and China, with no global consistency.Medical Express

"Gravity" and "Geomagnetism" Are Not Explanations

While the moon's tidal force is strong enough to move the oceans, it is far too weak to affect human physiology, and lunar cycle changes in geomagnetism or atmospheric pressure have not shown consistent effects. The most plausible explanation is "exposure to night light."Medical Express

Daylight Saving and the Moon — The Lesson is "Reduce Night Brightness"

While the impact of the full moon is small, the "artificially prolonged evening brightness" of daylight saving time has a much larger effect, delaying sleep and being associated with increased accidents and cardiovascular events. Ultimately, what most disrupts modern sleep is not the moon in the sky but the "light in our hands (screens)."Medical Express

How Did Social Media React? (Key Points)

• Spread of Dissemination: The same article distributed by The Conversation was reprinted in Chicago Tribune, SeattlePI, Yahoo! News, and shared on X (formerly Twitter) and Threads.Seattle Post-Intelligencer

• Wave of Personal Experiences: "I really can't fall asleep before a full moon," "My kids get excited," say the believers, while others argue, "No, it's because of smartphones," "Isn't caffeine/overtime the cause?" say the skeptics. On IG, posts stating "there is little decisive evidence that full moons worsen sleep" also spread.Instagram

• Excitement Among "Photo Enthusiasts": Separate from the debate, posts of full moon and supermoon photos grew on Reddit and X, coexisting with links to scientific explanation articles. Interest polarized not only in "sleep" but also in "viewing."Reddit

Note: Due to platform restrictions, the number of individual replies and the ratio of pros and cons on X/Threads cannot be scrutinized, so the above summarizes representative trends in post content (providing links to the original article and official account posts).X (formerly Twitter)

Practical Tips: Five Ways to Protect Sleep During Full Moon Week

1. Dim the Lights 90 Minutes Before Bed: Lower indoor lighting and use indirect lighting.

2. Screen Abstinence: Close screens an hour before bed, and if you must use them, switch to night mode and keep a distance.

3. Light Blocking Measures: Use double curtains or eye masks (especially effective outdoors or when camping).

4. Go to Bed and Wake Up at the Same Time: The "stubbornness" of the internal clock can absorb the weak lunar effects.

5. See a Specialist if Discomfort Persists: Consult a doctor if you experience snoring, severe daytime sleepiness, or strong mood swings.
   (Basis: The physiological mechanism that nighttime light causes sleep delay and melatonin reduction, and expert explanations)Medical Express
   
   

Research Notes: Positioning of Representative Evidence

• Synchronization of Lunar Phases and Sleep (Shorter and Later Before Full Moon): Science Advances (2021) and others.Science.org

• Suggestion of Gender Differences: Science of the Total Environment (2021/2022) suggests a relatively larger impact on men.ScienceDirect

• Classic Results from Indoor Experiments (30% Reduction in Deep Sleep / 5-Minute Delay in Sleep Onset / Total Sleep -20 Minutes): Current Biology (2013). Although there is debate about the interpretation, it aligns with the "light" hypothesis.Cell
  
  

Summary

While the full moon is not "completely without impact," its scale is small, and the main disruptor of our sleep is not moonlight but artificial light at night. However, for those with high vulnerability (adolescents, mood disorders, epilepsy, etc.), even a "slight shift" can trigger discomfort. During full moon week, self-care by reducing light, reducing screen time, and fixing wake-up times can be quite effective.Medical Express