As summer strikes Greenland, there is an increase in the suicide rates in the region, and now scientist have blamed the insomnia caused by incessant daylight for this trend.
The new research, led by Karin Sparring Bjorksten of the Karolinska Institutet in Sweden, studied the seasonal variation of suicides in all of Greenland from 1968-2002.
And it was found that there was a concentration of suicides in the summer months, and that the seasonal effect was specifically more in the North of the country - an area where the sun doesn't set between the end of April and the end of August.
Bjorksten said: "In terms of seasonal light variation, Greenland is the most extreme human habitat. Greenland also has one of the highest suicide rates in the world. We found that suicides were almost exclusively violent and increased during periods of constant day. In the north of the country, 82 percent of the suicides occurred during the daylight months (including astronomical twilight)."
The researchers found that most suicides occurred in young men, and that 95 percent of suicides were caused by using violent methods, such as shooting, hanging and jumping.
However, the researchers found no seasonal variation in alcohol consumption.
The authors speculated that light-generated imbalances in turnover of the neurotransmitter serotonin could lead to increased impulsiveness, which, in combination with lack of sleep, could explain the increased suicide rates in the summer.
"People living at high latitudes need extreme flexibility in light adaptation. During the long periods of constant light, it is crucial to keep some circadian rhythm to get enough sleep and sustain mental health. A weak serotonin system may cause difficulties in adaptation," said the authors.
Bjorksten concluded: "Light is just one of many factors in the complex tragedy of suicide, but this study shows that there is a possible relationship between the two."
The study has been published in the open access journal BMC Psychiatry.