Nordic countries Winter depression is a common slump in the mood of some inhabitants of most of the Nordic countries. Iceland, however, seems to be an exception. A study of more than 2000 people there found the prevalence of<unk>  and<unk>  changes in anxiety and depression to be unexpectedly low in both sexes. The study's authors suggested that propensity for<unk>  may differ due to some genetic factor within the Icelandic population. A study of Canadians of wholly Icelandic descent also showed low levels of<unk> . It has more recently been suggested that this may be attributed to the large amount of fish traditionally eaten by Icelandic people, in 2007 about 90 kilograms per person per year as opposed to about 24 kg in the US and Canada, rather than to genetic predisposition; a similar anomaly is noted in Japan, where annual fish consumption in recent years averages about 60 kg per capita. Fish are high in vitamin D. Fish also contain docosahexaenoic acid (DHA), which help with a variety of neurological dysfunctions. Other countries In the United States, a diagnosis of<unk>  was first proposed by Norman E. Rosenthal, M.D. in 1984. Rosenthal wondered why he became sluggish during the winter after moving from sunny South Africa to (cloudy in winter) New York. He started experimenting increasing exposure to artificial light, and found this made a difference. In Alaska it has been established that there is a<unk>  rate of 8.9%, and an even greater rate of 24.9% for subsyndromal<unk> . Around 20% of Irish people are affected by<unk> , according to a survey conducted in 2007. The survey also shows women are more likely to be affected by<unk>  than men. An estimated 3% of the population in the Netherlands suffer from winter<unk> .
Seasonal affective disorder
Major depressive episode
Major depressive disorder
Depression 
Late life depression
Premenstrual syndrome
Secondary mania
Postpartum depression