Abstract
Background: In Nigeria, there are not enough robust data on the association between chronotypes and certain sleep parameters, as well as association between chronotypes and psychological disorders. The present study determined the prevalence and sex distribution of chronotypes among undergraduate students in a university in Nigeria. It also determined the association between chronotypes and dream recall frequency (DRF), chronotypes and nocturnal sleep duration (NSD), chronotypes and excessive daytime sleepiness (EDS); and association between chronotypes and general psychopathology.
Methods: A sample of five hundred and twenty (520) students in a descriptive cross-sectional design, provided information on sociodemographic characteristics, dream recall frequency, and nocturnal sleep duration. In addition, they completed The Horne-Ostberg Morningness - Eveningness Questionnaire (MEQ), The Epworth Sleepiness Scale (ESS), and the 30–item General Health Questionnaire (GHQ - 30). Eventually, it was 513 subjects (98.65%) that provided complete data for analyses.
Results: The results showed that 21.5% and 25.7% of the subjects belonged respectively to early and late chronotypes while 52.8% of the subjects belonged to the neither early nor late (intermediate) chronotype. There was no preponderance of any sex in any of the chronotypes. The results further showed that the early chronotype was associated with better dream recall frequency and higher nocturnal sleep duration while the late chronotype (in addition to being associated with short sleep duration) was associated with a higher level of excessive daytime sleepiness and general psychopathology.
Conclusion: The study confirmed the findings in previous studies in other populations: an association between chronotypes and sleep disorders; as well as association between chronotypes and psychopathology. Late chronotype is significantly associated with sleep disorders and significantly associated with psychopathology. Policymakers and university administrators need to be aware of these in order to develop strategies that will enhance the mental health of individuals, especially students.

Key words: Chronotype, Sleep Parameters, Dream Recall Frequency, Sleep Duration, Excessive Daytime Sleepiness, Psychopathology