The Full Moon Effect in Mental Health: Myth or Reality?
A long-standing notion amongst some behavioral health professionals is that a full moon goes hand in hand with an increase in mental health patients and severity. But is there evidence to back this claim? MHO has previously shown that inpatients admitted to psychiatric programming during a full moon did not display more severe symptoms than inpatients admitted on any other day.
However, the staunchest of believers may still argue those experiencing increased mental health problems during a full moon could seek help in hospital emergency rooms rather than psychiatric facilities. To examine this angle, MHO analyzed a nation-wide behavioral health claims dataset containing 8,192,486 ER claims from 2022 through 2023, representing visits by patients with commercial insurance or Medicare/Medicaid claims [1]. Every which way we looked; we found no indication that anything is amiss during a full moon. The average number of BH ER visits during a full moon (12,659) was no different than when there wasn’t a full moon (12,582). The month in which a given full moon occurs also does not impact the average BH ER visit count.
Figure 1. Count of ER visits by month and full moon (non-interactive graph)
Even the diagnostic category breakdown of BH ER visits does not change during a full moon (see Table 1).
Table 1. Diagnostic Category Breakdown by Moon Type
“But my hospital does get hit hard during full moons!”
Well, not so fast. Comparing quarterly average full moon visit counts to average daily non-full moon visit counts in the same quarter, the average individual facility saw only a .03 visit volume increase on full moon days. In practical terms, this is no difference in visit volume for the average facility. Did some hospitals in some quarters have a full moon visit volume well above their quarterly non-full moon average? Yes, there are numerous instances of where an individual hospital had 20, 30, and even 50 patients above their quarterly average. However, visit volume for individual non-full moon days can and does vary by those same amounts (and larger). Additionally, there are numerous instances of hospitals averaging many fewer BH ER visits during a full moon.
Figure 2. ER visit counts during full moon days vs. non-full moon days (interactive graph)
Rather than any actual, data backed differences on full moon nights, it’s likely those who believe there is an association between full moons and patient volume, or severity simply remember specific cases when there is a full moon to “blame”. After all, a full moon is a prominent feature in the night sky, inspiring countless stories and myths. However, while not as poetic or captivating, data tell a different story. Even when examining multiple metrics across several years, looking at individual facilities and overall data, there is no indication BH ER visit volumes are anything but normal when there is a full moon.
Footnotes
[1] Data source: Trilliant Health
