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PUBLIC RELEASE DATE:
7-May-2009

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Contact: Graeme Baldwin
graeme.baldwin@biomedcentral.com
44-078-774-11853
BioMed Central
@biomedcentral

Constant sunlight linked to summer suicide spike

Suicide rates in Greenland increase during the summer, peaking in June. Researchers writing in the open access journal BMC Psychiatry speculate that insomnia caused by incessant daylight may be to blame.

Karin Sparring Björkstén from the Karolinska Institutet, Sweden, led a team of researchers who studied the seasonal variation of suicides in all of Greenland from 1968-2002. They found that there was a concentration of suicides in the summer months, and that 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. Björkstén 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% of the suicides occurred during the daylight months (including astronomical twilight)".

The researchers found that most suicides occurred in young men and that violent methods, such as shooting, hanging and jumping, accounted for 95% of all suicides. No seasonal variation in alcohol consumption was found. The authors speculate that light-generated imbalances in turnover of the neurotransmitter serotonin may lead to increased impulsiveness that, in combination with lack of sleep, may explain the increased suicide rates in the summer. They said, "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".

Björkstén concludes, "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."

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Notes to Editors

1. Accentuation of suicides but not homicides with rising latitudes of Greenland in the sunny months
Karin S Björkstén, Daniel F Kripke and Peter Bjerregaard
BMC Psychiatry (in press)

During the embargo, article available here: http://www.biomedcentral.com/imedia/1819690397250889_article.pdf?random=327995

After the embargo, article available at journal website: http://www.biomedcentral.com/bmcpsychiatry/

Please name the journal in any story you write. If you are writing for the web, please link to the article. All articles are available free of charge, according to BioMed Central's open access policy.

2. BMC Psychiatry is an open access journal publishing original peer-reviewed research articles in all aspects of the prevention, diagnosis and management of psychiatric disorders, as well as related molecular genetics, pathophysiology, and epidemiology. BMC Psychiatry (ISSN 1471-244X) is indexed/tracked/covered by PubMed, MEDLINE, CAS, Scopus, EMBASE, PsycINFO, Current Contents, Thomson Reuters (ISI) and Google Scholar.

3. BioMed Central (http://www.biomedcentral.com/) is an STM (Science, Technology and Medicine) publisher which has pioneered the open access publishing model. All peer-reviewed research articles published by BioMed Central are made immediately and freely accessible online, and are licensed to allow redistribution and reuse. BioMed Central is part of Springer Science+Business Media, a leading global publisher in the STM sector.



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