While the purported link between behavior and the phases of the moon appears to be an old wives' tale, a new study by Thomas Schory et al. does suggest a connection between weather and psychiatric symptoms.
The researchers obtained data on suicides and violent crimes during 1999 in the Louisville area, as well as data on documented emergency psychiatric visits and psychiatric admissions at the University of Louisville Hospital that year. They then studied the association between these events and humidity, wind speed, and barometric pressure.
"The data suggest that total numbers of acts of violence and emergency psychiatry visits are significantly associated with low barometric pressure," they report. "Psychiatric inpatient admissions and suicides are not associated with any of the weather variables investigated." Their findings may indicate, they say, that low barometric pressure is associated with impulsivity.
Schory et al. note that low barometric pressure is associated with changes in cerebral blood flow, increased risk of rupture of intracranial aneurysms, premature labor, changes in the norepinephrine metabolite HMPG (at least in women), and changes in cerebrospinal fluid concentrations of the serotonin metabolite 5-HIAA in people with depression. They also note that weather fluctuations are known to influence certain mental disorders, including seasonal affective disorder (SAD) and bipolar disorder.
The researchers hypothesize that "barometric pressure may alter the propensity toward impulsive behavior through changes in brain monoamines or cerebral blood flow."
"Barometric pressure, emergency psychiatric visits, and violent acts," Thomas J. Schory, Natasha Piecznski, Sunil Nair, and Rif S. El-Mallakh, Canadian Journal of Psychiatry, Vol. 48, October 2003, 624-7. Address: R. S. El-Mallakh, Mood Disorders Research Program, Department of Psychiatry and Behavioral Sciences, University of Louisville School of Medicine, Louisville, KY 40292, firstname.lastname@example.org.