for National Geographic News
The dreaded blues of dark winter months have long been blamed for seasonal depression, but too much sunshine may have an even more dire effect.
In northern Greenland more than 80 percent of suicides occur in summer, during which the sun barely dips below the horizon.
"There is so much light that people can't take it," said lead study author Karin Sparring Björkstén of the Karolinska Institutet in Sweden.
The researchers studied records of causes of deaths—1,351 due to suicide—between 1968 to 2002 in Greenland, which is largely above the Arctic Circle.
When they looked at the data on a month by month basis, it became clear that suicides were far more frequent in summer, particularly in the north, where the extended summer days are most pronounced.
Of the 33 suicides that had occurred in the most northerly province, Avannaa (North Greenland), 82 percent had happened during the period of 24-hour sunlight, March 7 to October 8. (Avannaa disappeared from maps in early 2009, when Greenland's administrative divisions were revised.)
(Related: "'Death Maps' Pinpoint Mortality Causes.")
Dangers of 24-Hour Living
Across Greenland, a province of Denmark, 80 percent of the suicide victims were men. Ninety-five percent of the victims took their lives in violent ways—shooting themselves, hanging themselves, or jumping, for example. There was no evidence that the summer increases were related to depressive disorders or increased alcohol consumption.
Björkstén and her colleagues believe the increase in summer suicides is related to lack of sleep.
"People live their lives differently during the Arctic summer. Farmers plough their fields in the middle of the night, and children are out playing after midnight. They lose their daily rhythm," Björkstén said.
Other countries may not have the extreme seasonal sunlight variations, but anyone can learn from the new research, she said.
"Today's 24-hour society is not good for us. Public health would improve if people cared more about their sleep," said Björkstén.
Findings published today in the journal BMC Psychiatry.
SOURCES AND RELATED WEB SITES