Lighting, Mood, and Seasonal Fatigue in Northern Argentina. Comparison to Countries Close to and Further from the Equator

Abstract: The main problems in this thesis concern the impact of seasonal variations in daylight and ambient temperature on people's mood and the prevalence of various symptoms related to seasonal affective disorder. Questions are also raised about the role of the indoor environment and of the individual's personality as moderators of such an impact. In contrast to most previous research, the present study was carried out in a location fairly close to the equator, namely northern Argentina. However, for the sake of comparison, the data also have been related to data from some other countries close to and further from the equator. The work was part of a large multi-national research project carried out in Sweden, England, Saudi-Arabia, and Argentina during a three year period on a total sample of 988 non-clinical individuals from basically healthy working populations. Taken together, the results lend considerable support to the assumption that the seasonal variations in day length may be the most important factor behind SAD symptoms. However, in the two countries close to the equator, temperature also seemed to be of considerable importance. The results show that the prevalence of sadness was common in Sweden and England, but less common and less severe in Argentina and Saudi Arabia. In the specific case of Northern Argentina, workers' mood was affected more by the indoor lighting and decoration than by the season of the year in spite of the considerable variations in daylength. Concerning the individual characteristics, the results confirmed the existence of a link between seasonality and personality as well as the higher vulnerability in females than in males found in previously studies. For interior designers and architect it is important to realise that depressed mood may be more common in dark and colourless indoor environments.