Self-reported mental distress under the shifting daylight in the high north

The validity of the concept of seasonal affective disorder and the causal link to lack of daylight in winter is controversial. There is a need for investigations in large samples of the general population at different latitudes and within general research contexts to avoid selective response bias and sensitization of the population.

During a study of health effects of the air pollution from Russia in a small community at 70 degrees north, a self-administered questionnaire was filled in by 3736 inhabitants, 60.8% of the total population between 18 and 69 years. Three questions concerned depression, sleeping problems and other problems related to the two contrasting seasons with regard to daylight.

Twenty-seven per cent reported to have some kind of problem in the dark period. Most frequently reported were sleeping problems during winter, in 19.9% of women and 11.2% of men. Self-reported depression in winter was found in 11.1% of women and 4.8%% of men. Sleeping problems increased with age, while depression was most often reported by middle-aged people. The only other reported problem in winter was fatigue. The adjusted relative risk (RR) for winter depression in women compared to men was 2.5 (95% confidence interval: 1.9-3.2). Very few had problems in summer.

In the high north, one-third of the women and one-fifth of the men experience problems with sleep, mood or energy related to season. The prevalence of self-reported depression was surprisingly low in winter considering the lack of daylight.