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Constant sun -- too much of a good thing?

2009-05-09 04:18:04

Fri May 8, 10:59 am ET

LONDON (Reuters) Too much sunlight in places like Greenland where long summer

days often cause insomnia appears more likely to drive a person to suicide,

Swedish researchers said Friday.

Despite a belief that suicides tend to rise in late autumn and early winter

months because of darkness, the new findings suggest that places where constant

sunlight in summer seasons is a fact of life 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

BioMed Central journal BMC Psychiatry.

According to the World Health Organization, 877,000 people worldwide kill

themselves each year. For every suicide death, anywhere from 10 to 40 attempts

are made, the U.N. agency estimates.

Scientists have previously linked sleep disturbances to increased suicidal risk

in people with psychiatric disorders and in adolescents but it is unclear

whether the association also exists in the general population.

The Swedish team studied the seasonal variation of suicides in all of 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."

Most of the suicides involved young men and were violent -- such as shooting,

hanging and jumping from high places. These kinds of deaths accounted for

nearly all, about 95 percent, of the suicides.

The researchers speculated that light-generated imbalances in serotonin -- the

brain chemical linked to mood --may lead to increased 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.

(Reporting by Michael Kahn; Editing by Maggie Fox)