The role of psychological mechanisms to insomnia in its early phase: a focus on arousal, distress, and sleep-related beliefs.

The aim of this study was to investigate whether arousal, distress, and sleep-related beliefs are related to the development of insomnia. From a randomly selected sample of 3600 individuals from the general population (50-60 years), 2239 participants filled out a baseline and 1-year follow-up questionnaire. Logistic regression and cluster analysis were used to investigate whether the psychological mechanisms were related to the development of new cases of insomnia over 1 year and whether it was possible to classify the participants based on their profiles of psychological mechanisms. The results showed that arousal, sleep-related beliefs, and depression were significantly related to the development of new cases of insomnia (13% of the variance). High scores on all three mechanisms were characteristic of one cluster (18% new cases of insomnia) and low scores on the mechanisms of another cluster (5% new cases of insomnia). This study shows that arousal, sleep-related beliefs, and depression are associated with the development of insomnia, and that psychological mechanisms often co-occur in individuals who develop insomnia.