Background. 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.
Methods. During a study of health effects of the air pollution
from Russia in a small community at
70° 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.
Results. 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.
Conclusions. 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.