Is there a negative impact of winter on mental distress and sleeping problems in the subarctic: The Troms？ Study

The cross sectional population Troms？ Study was conducted in Troms？, North Norway, at 69.4 degrees North and above the Arctic Circle. The study included entire birth cohorts and random samples of the population aged 30 to 87 years. Data was collected continuously from 1 October 2007 to the end of December 2008 except July. 8951 persons completed questionnaires including the HSCL-10 and the MCTQ.There were no significant differences in the reporting of current mental distress depending on season. Significantly more reported current sleeping problems in winter than in the other seasons, and less sleeping problems was found in spring.In this sub-arctic population, insomnia was most prevalent in winter, but there were no significant seasonal differences in mental distress. Although some people in the sub-arctic clearly are mentally negatively affected by the darkness of winter, the negative impact of winter on mental distress for the adult population is not conclusive.Many studies have focused on seasonality of mental distress and psychiatric symptoms, and in 1984, Rosenthal et al. [1] first described the syndrome Seasonal Affective Disorder (SAD). The condition is known as ‘winter depression’ due to a predictable onset in the autumn/winter months and a spontaneous remission in the spring/summer period.Chronobiological mechanisms related to circadian rhythms, melatonin, serotonin, and retinal photosensitivity have been claimed to play a significant role in many cases of seasonal mood variations because of the described linkage between the syndrome and the lack of daylight in winter [2-5].Seasonal differences in daylight also influence sleep in many ways. The term ’insomnia’ is often defined as an individual’s report of difficulty with sleep or used to describe the presence of polysomnographic evidence of disturbed sleep. Insomnia symptoms are of the most frequent complaints in the general population with prevalences from 10–50% depending in part on definitions and data-