Does the full moon really change how people behave?

Research has not found a consistent effect of the full moon on human behavior. Reviews that pooled many studies found the full moon unrelated to crimes, suicides, psychiatric problems and crisis center calls, and a large 2026 study of psychiatric emergencies in France reached the same conclusion. Small effects cannot be entirely excluded, but none has held up well under scrutiny. [1] [2]

In 1985, psychologists James Rotton and Ivan Kelly reviewed 37 studies in the journal Psychological Bulletin, in a paper titled "Much Ado about the Full Moon." Combining the results statistically, a method called meta-analysis, they found no relation between the full moon and crimes, suicides, psychiatric problems or crisis center calls. They concluded that further research on the question was unnecessary. A 1992 review of 20 studies of suicide likewise found no lunar effect, and noted that earlier studies often failed to account for variation by day of the week. [1] [3] [4]

One 1982 study reported more traffic accidents on full-moon nights. The problem was that full moons in that period fell more often on weekends, when more people drive. After the authors reanalyzed the data to remove that confounding factor, the lunar effect disappeared. [1]

A study published in March 2026 analyzed 69,764 consultations at a large psychiatric emergency department in Paris between 2016 and 2023. It found no statistically significant link between lunar phases and the number of consultations, hospital admissions, reasons for consultation or specific disorders, using four different definitions of lunar exposure. A Canadian study of a 252-bed psychiatric hospital covered seven years, 627,763 patient days and 7,153 behavioral incidents. Incidents rose and fell from one lunar day to another, but with no pattern and no statistically significant variation. [2] [5]

The Paris authors note limits. The study was done at a single urban site, where moonlight may matter less than in rural areas, and diagnostic coding in emergency rooms can be imprecise. They say very small effects cannot be completely ruled out, though any such effects would probably have little clinical relevance. They suggest future work look at individual vulnerabilities, such as disrupted circadian rhythms or sensitivity to light at night. [2]

Psychologists point to illusory correlation, a term coined by Loren and Jean Chapman for seeing an association that does not exist. When something odd happens during a full moon, people notice and remember it because it fits their expectations. When nothing odd happens, the event fades. One study found that psychiatric nurses who believed in the lunar effect wrote more notes about patients' unusual behavior than nurses who did not. The Paris authors add that the full moon's long cultural symbolism may play a part. [1] [2]

Some persistent critics dispute the 1985 conclusion and point to a few positive findings in scattered studies. The reporting here says those findings have not survived closer investigation. The authors of the Canadian study also warn that the belief may add to the stigma faced by people with mental illness. [1] [5]