Type of Document	Thesis
Author	Bernert, Rebecca Ann
URN	etd-11142005-112652
Title	A Circadian Vulnerability for Depression: Eveningness and Sleep Variability
Degree	Master of Science
Department	Psychology, Department of
Advisory Committee	Advisor Name Title Thomas Joiner Committee Chair Frank Johnson Committee Member Janet Kistner Committee Member
Keywords	Diurnal Preferences Mood Disturbances Sleep Rhythms
Date of Defense	2005-07-20
Availability	unrestricted
Abstract Circadian rhythms describe behavioral and biological variables that demonstrate a periodicity of approximately 24 hours. Although such rhythms show consistent 24-hour patterns, differences exist in the timing of circadian phase position. Extreme diurnal preferences are referred to as eveningness and morningness. Despite a growing interest in the study of circadian rhythm abnormalities and psychopathology, diurnal preferences have been relatively understudied in depression. The present study examined these preferences in a sample of 82 college undergraduates. Due to a presumed desynchrony between sleep and circadian preference, evening types were hypothesized to show increased sleep variability and the highest levels of depressive symptoms. Sleep variability was expected to mediate the link between eveningness and depressive symptoms. Results first revealed that diurnal preferences did not significantly predict depressive symptoms, although this association emerged as a nonsignificant trend (p = .08). Next, diurnal preferences significantly predicted sleep variability (p = .03). Sleep variability did not uniquely predict depressive symptoms, although this link also emerged as a non significant trend (p = .05). Finally, a mediation model was not supported at the p < .05 level (p = .15).
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