The full moon increases crime and ER visits
Decades of research have found no reliable association between full moon phases and emergency room visits, violent crime, psychiatric admissions, or other behavioral outcomes. The belief persists due to confirmation bias, not evidence.
What we know
The lunar effect hypothesis, sometimes called the Transylvania effect, proposes that the full moon influences human behavior through gravitational or light-based mechanisms. It has been tested in numerous studies across different settings and populations, and the evidence consistently fails to support it.
A comprehensive 30-year literature review of studies examining lunar phases and cardiac events, brain aneurysms, kidney stones, psychiatric emergencies, childbirth, and general ER visits found no correlations. A 2025 study published in the Journal of Orthopaedic Surgery and Research analyzed trauma emergency department admissions over an extended period and found no statistically significant association with moon phases. A 1996 study in Annals of Emergency Medicine specifically examining ER visits during full moons found no effect.
The persistence of the belief among healthcare workers and the general public is well-documented and is attributed to confirmation bias: people remember full moons on chaotic nights and forget quiet full-moon nights. The full moon is visually striking and memorable, so it becomes an anchor for unusual events. Controlled studies that remove this bias consistently show no lunar effect.
The gravitational pull of the Moon, while substantial on ocean tides, is negligible at the cellular or organismal level compared with nearby objects. The full moon also provides more light at night, which in theory could influence outdoor activity rates, but this effect has not been demonstrated to cause meaningful changes in behavior in controlled analyses.
Common claims
- ER visits spike during a full moonFalse - studies find no association
- The full moon causes psychiatric crisesNot supported by controlled evidence
- Crime rates increase during a full moonNot replicated in controlled studies
- Many healthcare workers believe in the lunar effectTrue, but belief doesn't equal evidence
Evidence hierarchy
All sources
- No influence of moon phases on emergency trauma admissionsJournal of Orthopaedic Surgery and Research · 2025
- The full moon and ED patient volumes: unearthing a mythPubMed · 1996
- Is the ER really any wilder during a full moon?The DO (American Osteopathic Association) · 2021
- Do Emergency Room Visits Increase During a Full Moon?University of Texas Austin · 2019