Conscientiousness is a predictor of diurnal preference.

The relationship between diurnal preference, as measured by the Horne-Ostberg questionnaire, and quantifiable personality traits was investigated in 617 participants. A hierarchical multiple regression analysis demonstrated that out of the personality variables, conscientiousness was the single biggest predictor of diurnal preference (beta=0.246), after controlling for depression, sleep disorders, shift work, age, gender, and demographic characteristics. Morningness has previously been associated with physiological parameters of the circadian clock and with polymorphisms in circadian clock genes, suggesting the possibility that conscientiousness, too, may be linked to the same parameters.