Do Behavioral Health Visits Correspond to the Full Moon?

March 26, 2015  |  David White

We’ve always heard that behavioral health emergency department visits correspond to the full moon. Because a literature review found no significant correlation, we decided to delve into the data to see for ourselves. Our quick and dirty informal analysis revealed some surprising conclusions.

We gleaned arrival patterns for 120,000 behavioral health patients from two emergency departments. To view and manipulate the data, click here. You may select one or both facilities and the category of behavioral health patient in the center pull-down menus.  The bar charts at the top indicate monthly total behavioral health volumes.  The lower chart displays daily volumes. The black full moon icons on the lower chart indicate the full moon dates, and the brown footballs indicate game days for Facility B.

We conclude from the data that fewer behavioral health patients presented to the ED on full moon days than the monthly average volume. We found no measurable difference between the number of full moon visits on weekdays versus weekends.

Full moon data table - BH2

Yet, patients in the ‘Psych Evaluation’ subcategory visited the ED 9% more than the monthly average on full moon days. (These patients exhibit mental illness or depression but not substance abuse or suicide risk.)

On full moon days that fall on Sunday through Thursday, Psych Evaluation patients visit 17% more often.

Full moon data table - PE2

Psychiatric Evaluation patient visits average 8-12 hours versus 2-3 hours for other patient types. These longer turnover times mean that a hospital needs more behavioral health treatment rooms.

Psychiatric patients need more staff resources than a typical ED patient. They need a Social Worker to administer an evaluation, and perhaps a sitter or security officer to prevent self harm.

While a volume increase caused by the full moon sounds frivolous, 17% more patients can confound flow and staffing.


Have you noticed a volume increase during the full moon in your emergency department? We invite you to share your experience in the comments below.

David White MBA, LEAN/DFSS Certified
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