CIRCADIAN TYPOLOGY AND INDIVIDUAL-DIFFERENCES - A REVIEW

This paper reviews studies which have dealt with the relationship between morningness-eveningness (circadian typology) and other individual differences such as age, sex, personality dimensions and work schedule of their subjects. It appeared that the changes in the morningness-eveningness preference covaried with the age related changes in the internal body clock. An older age was associated with morningness while younger subjects tended towards eveningness, the critical age for the circadian typology change was 50 years. Sex-related differences are too small to be reflected in the scores on circadian typology questionnaires, although women were ahead of men by 1 hr in their circadian rhythms. The results on work schedule proved its role as a synchronizer modifying the morningness factor. The morningness dimension and extraversion are probably related through the impulsivity subdimension, which is closely associated with brain activation. Further research is needed to clarify the relationship between morningness and other personality dimensions (neuroticism, psychoticism), because the results are inconclusive. The influence of circadian typology on the tolerance to shift work and life habits are also discussed. The results with regard to shift work revealed the importance of morningness in determining human tolerance and health complaints. As regards life habits, there were differences in various aspects related to circadian typology especially psychoactive substances consumption.