Seasonal variation in self-reported arousal and subjective health complaints

Many aspects of human physiology and behavior are seasonally related. Although there are many studies using self-ratings of, for example, subjective health and stress, few involve adjusting effects for seasonal differences. To estimate the need of adjusting for season in field studies, 24 healthy men and women were studied in a design that required them to fill in questionnaires on one workday every month, for 12 consecutive months. The results showed that ratings of stress were higher during winter and early spring, but only in the early afternoon and not in the morning or the evening. While some subjective health complaints were rated higher during winter, the ratings of energy and self-rated health did not vary throughout seasons. This concludes that seasonal variations may be a source of bias in questionnaire studies. Yet, further studies are needed to more definitely sort out which phenomena and self-rating measures that co-vary with season.