Improvement in mental health over time in Northern Norway

Background There are very few prospective studies of mental distress in the general population.Two studies of general health in Finnmark county in northern Norway, performed 9 years apart, contained questions about depression and sleeping problems, which made it possible to study change in mental distress over time in the general population. Methods In a self-administered questionnaire, the subjects were asked about depression and sleeping problems, both generally and related to the dark period in winter, at two points in time: in 1987/88 and 1996/97. The persons participating in the two surveys were partly the same and partly new individuals. More than 12,000 persons responded in 1987/88 and more than 7,000 people in 1996/97. The cohort that answered questions about sleeping problems and depression at both time-points consisted of 3,318 and 3,682 persons, respectively. Results The prevalence of depression and sleeping problems,both generally and related to winter,decreased significantly in the course of the 9-year time-span. The decrease was also true for the cohort that answered at both time-points, except for sleeping problems related to winter, which were unchanged. The pattern of changes was identical for both genders and all age groups. Conclusions Mental health in the general population seems to have improved during the period studied. The findings are also relevant for the discussion of the validity of the concept Seasonal Affective Disorder, and the presumed connection to light-deprivation.