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Excessive sunlight is linked to suicide risk

TOO much sunlight in places such as Greenland - where long summer days often cause insomnia - appears more likely to drive a person to suicide, Swedish researchers said yesterday.

Despite a belief that suicides tend to rise in late autumn and early winter months because of shorter daylight hours, the new findings suggest constant sunlight in summer seasons may be just as dangerous.

"During the long periods of constant light, it is crucial to keep some circadian rhythm to get enough sleep and sustain mental health," Karin Sparring Bjorksten, of the Karolinska Institute in Sweden, and colleagues reported in the journal BMC Psychiatry.

Scientists have previously linked sleep disturbances to increased suicidal risk in people with psychiatric disorders and in adolescents. It is unclear whether the association exists in the general population.

The Swedish team studied the seasonal variation of suicides in Greenland from 1968 to 2002 and found a cluster of suicides in the summer months.

This seasonal effect was especially pronounced in the north of the country - an area where the sun doesn't set between the end of April and the end of August.

"We found that suicides were almost exclusively violent and increased during periods of constant day," Bjorksten said in a statement.

"In the north of the country, 82 percent of the suicides occurred during the daylight months."

The researchers said light-generated imbalances in serotonin - a chemical linked to mood - may lead to impulsiveness that in combination with a lack of sleep drives people to kill themselves.

"Light is just one of the many factors in the complex tragedy of suicide, but this study shows that there is a possible relationship between the two," Bjorksten said.


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