Association Between Low Barometric Pressure and Completed Suicides

To the Editor: Associations between low barometric pressure and behavior have been previously demonstrated, including associations with both violence and suicide attempts (1, 2). We extend those associations to completed suicides in the first North American study with an adequate sample size of 714 completed suicides.

The Jefferson County, Ky., medical examiner’s office provided information regarding the dates of completed suicides between January 2000 and December 2011. Meteorological data were obtained from the Louisville office of the National Weather Service for this same 11-year period.

There were 714 completed suicides in the 11 years studied. Information on age, gender, and method of suicide was not available. Barometric pressure was lower on days with completed suicides than on days without any completed suicides (29.48 inHg [SD=0.038], compared with 29.53 inHg [SD=0.0036], respectively; p<0.0001, t=2.44). Neither average daily temperature (59.1°F [SD=0.67] for suicide days, compared with 58.1°F [SD=0.37] for nonsuicide days; p=0.63, t=0.92) nor solar radiation (6.95 MJ/m² [SD=0.11] for suicide days, compared with 6.96 MJ/m² [SD=0.06] for nonsuicide days; p=0.09, t=0.13) showed a relationship to completed suicide.

A multitude of biological, psychological, social, and environmental factors can play a role in a person’s decision to commit suicide. Although we have demonstrated a significant association between lower barometric pressure and completed suicide, the mechanism of the effect—which has now been demonstrated worldwide (3–5)—remains to be determined.