• Korean Journal of Biological Psychiatry
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• v.22 no.3
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• pp.135-139
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• 2015

Objectives The purpose of this study was to investigate the relationships among circadian typology, bipolarity and life satisfaction of university students. Methods A total 1232 participants completed questionnaires, which included Composite Scale of Morningness (CSM), Satisfaction with Life Scale (SWLS), and Mood Disorder Questionnaire (MDQ). Statistical analyses were done using correlation analysis, and analysis of covariance. Results The CSM score was positively associated with SWLS score (r = 0.232 ; p < 0.001). The morningness group has higher life satisfaction than the eveningness group (p < 0.001). The eveningness group has higher bipolarity than the morningness group (p < 0.001). The CSM score was negatively associated with MDQ score (r = -0.128 ; p < 0.001). Conclusions Bipolarity and life satisfaction were associated with circadian typology. Morningness was the important determinant of life satisfaction and bipolarity.

• Korean Journal of Biological Psychiatry
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• v.21 no.3
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• pp.93-98
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• 2014

Objectives Circadian rhythms have been known to have associations with psychiatric disorders and personality traits. The present study investigated the relationships between circadian typology and temperaments/characters in a non-clinical Korean population. Methods Two hundred six healthy Korean college students (male 109, female 97) participated in this study. The subjects completed the Composite Scale of Morningness for circadian typology and 140-item Temperament and Character Inventory-Revised-Short version (TCI-RS). Results Multivariate analyses of covariance showed a significant association between chronotypes and temperamental dimensions of the TCI-RS. Morning types were significantly associated with lower harm avoidance and higher persistence and self-directedness dimensions, compared to evening types and intermediate types. No interaction effects between sex and chronotypes were shown for temperamental dimensions. Conclusions The present findings suggest that high persistence and self-directedness characters are related to morning types and high harm avoidance temperament is more related to evening types.

• Korean Journal of Biological Psychiatry
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• v.23 no.4
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• pp.173-178
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• 2016

Objectives The purpose of this study was to investigate the relationships among circadian types, depressive mood and internet addiction and to identify the mediating effect of depressive mood between circadian types and internet addiction in Korean College Students. Methods A total of 2632 participants completed questionnaires, which included the Korean translation of the Composite Scale of Morningness (CSM), the Patient Health Questionnaire (PHQ-9), and the Korean version of the Internet Addiction Test (KIAT). Statistical analyses were done using correlation analysis, analysis of covariance and multiple linear regression. Results The CSM score was negatively associated with the PHQ-9 score (r = -0.226, p < 0.001) and the KIAT score (r = -0.218, p < 0.001). The eveningness group showed higher scores in depressive mood and internet addiction than the morningness group (p < 0.001). Depressive mood showed a partial mediating effect between circadian types and internet addiction (${\beta}=0.255$, p < 0.001). Conclusions Internet addiction was associated with circadian types and depressive mood. These results suggest that depression and circadian rhythm management would contribute to the prevention of internet addiction.

• Sleep Medicine and Psychophysiology
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• v.22 no.2
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• pp.53-56
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• 2015

Good sleepers tend to more resilient than poor sleepers. As sleep and resilience may have a bidirectional relationship, it is important to explore the relationship between healthy sleep and resilience. Objectively and subjectively measured sleep quality showed positive association with resiliency. In one study, more resilient adolescents had higher sleep efficiency, less light sleep, more slow-wave sleep, and a smaller number of awakenings after sleep onset. Circadian typology, jetlag and circadian misalignment may be associated with the capacity to deal with adversity. Eveningness, exposure to chronic jetlag and circadian misalignment might be risk factors for development of psychological problems and mental disorders. Additional studies are needed to evaluate whether promoting healthy sleep behaviors results in increased resilience.

• Interdisciplinary Bio Central
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• v.3 no.4
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• pp.13.1-13.8
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• 2011

Previous research has established the existence of individual differences with regards to individuals' optimum time of well-functioning; specifically in terms of being either morning or evening oriented. An association has also emerged between being more evening, as opposed to morning, oriented and having a greater number of sexual partners. The aim of the present study was to investigate whether "eveningness" in males is an evolved sexually dimorphic trait consistent across different cultures. A sample of 179 male Sri Lankan men residing in two different cultural and economic settings, Italy and Sri Lanka, were administered the Morningness-Eveningness Questionnaire (MEQ) followed by assessing their sexual behavior history. The results robustly portrayed a highly significant main effect of MEQ types highlighting the twofold sexual success enjoyed by the evening individuals in both regional locations. Morning oriented individuals, showed a stronger preference for going out and partying than evening-types, suggesting that the higher mating success of evening types is not due to their different lifestyles allowing more opportunities to encounter females. However, evening types exhibited a preference for flirtatious behaviors in the later part of the day. Shoulder-to-hip and handgrip strength, as measures of testosterone levels, were not significantly associated with eveningness. The results are discussed in terms of sexual selection and its interplay with human cultural variation.

• Sleep Medicine and Psychophysiology
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• v.26 no.1
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• pp.5-15
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• 2019

Chronotype (CT) is defined as an inter-individual difference in sleep-wake cycles and daily activities. Previous studies have suggested that this individual difference can influence our biological and psychological functioning. Literature regarding the psychometric properties and validity of CT measures are reviewed. We provide an overview of biological indicators (sleep-wake cycle, body temperature, cortisol, and melatonin) that are used for distinguishing two chronotypes: morningness (MT) and eveningness (ET). We also review the differences between CT in relation to personality traits and the occurrence of psychopathology. In addition, the methodological limitations of studies on CT are discussed. Finally, future research directions in terms of CT are proposed.

• Sleep Medicine and Psychophysiology
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• v.22 no.2
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• pp.64-69
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• 2015

Objectives: We investigated whether sleep behaviors, severity of insomnia and circadian typology are associated with quality of life among Gyeongsang National University (GNU) medical students. Methods: Questionnaires were distributed to 46 fourth-year students of GNU Medical School. The hospital anxiety-depression scale, insomnia severity index (ISI), morningness-eveningness questionnaire (MEQ) and WHO Quality of Life-BREF (WHOQOL-BREF) were used. Results: Quality of life in terms of physical health was associated with age, weekday total sleep time (TST), weekend TST, catch up sleep, depression, ISI score, and MEQ score. Quality of life in terms of psychological health was correlated to weekday and weekend TST, anxiety, ISI score and MEQ score. Sex, weekday TST, depression, and ISI score were revealed to influence the social aspect of quality of life, and weekday and weekend TST, and ISI score were associated with quality of life in terms of environment. Multiple regression analysis showed that better sleep quality predicted to a higher quality of life in terms of physical, psychological and environmental health, and eveningness was associated with a better quality of life in terms of physical and psychological health. Conclusion: It is concluded that physical, psychological, and environmental aspects of quality of life were associated with quality of sleep and that physical and psychological aspects of quality of life were related to eveningness in GNU medical students. Therefore, it is equally important to treat emotional problem as well as improve sleep quality.