Background: Studies on creativity and mental illness and reports on Seasonal Affective Disorder in artist often have methodological weaknesses; in particular they tend to be retrospective. Knut Hamsun was an original writer and Nobel Prize winner in literature. Anecdotes from his life suggest that he suffered from SAD. Prospective methods were used to investigate if Hamsun revealed seasonal variations in mood.
Methods: 3318 of Hamsuns’s letters are published and stored electronically in a word processing format. Two different approaches were used to examine if seasonal variations in mood were reflected in Hamsun’s letters. The letters were searched for words describing positive and negative mood states, and the occurrence of these words were analysed in relation to seasons. Secondly, two blind raters classified letters as either reflecting elevated- or depressed mood, and the association between mood and seasons was analysed.
Results: Seasons had no major effect on the frequency of positive and negative words in Hamsun’s letters. There were more letters with a cheerful or elated mood written in summer than in winter; and more letters reflecting a negative mood written in winter than in summer. However, this was not statistically significant.
Discussion: In this study we were able to circumvent several of the methodological problems encountered in previous studies of mental disorders in creative artists. Although our analysis of Hamsun’s letters did strongly indicate that he had marked seasonal variation in mood, we were not able to positively confirm this since the statistical analyses did not reach two tailed significance.