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Clock Genes, Circadian Rhythms, and Mood Disorders: The Role of Positive Affect

Miller, Megan A. (2014) Clock Genes, Circadian Rhythms, and Mood Disorders: The Role of Positive Affect. Master's Thesis, University of Pittsburgh. (Unpublished)

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Background: The master circadian clock maintains a ~24 hour rhythm via genetic feedback loops. Polymorphisms in master clock genes have been associated with markers of delayed rhythms and depression, suggesting delayed rhythms originating from variants in the master clock may create vulnerability to depression. Further, evening chronotype, a marker of delayed rhythms, is associated with depression. Recent research has found positive affect (PA) to be an important mediator in the relationship between evening chronotype and depression severity. PA exhibits a diurnal rhythm that is delayed and blunted in those with evening chronotype, suggesting the same master clock polymorphisms that predict chronotype may also predict PA rhythms. Therefore, it is hypothesized that polymorphisms in master clock genes will predict variations in PA rhythms and further, chronotype will mediate this relationship. Methods: Affect was measured every 45 minutes during waking hours for at least two workdays and one non-workday in 381 healthy Caucasian adults. Participants completed questionnaires on affect and chronotype. Genetic information was extracted from blood samples and genotyped for four polymorphisms (CLOCK 3111 C/T, PER3 G647V, BMAL 1420 A/G, CRY1 rs8192440) that were used to create a gene risk score. Results: The PA rhythm on workdays differed significantly based on chronotype. PA phase timing, but not amplitude, significantly differed across chronotype. The proposed clock gene risk score did not predict either PA rhythm measures or chronotype. Discussion: Study results support the association between chronotype and PA rhythm, specifically in phase timing. Although the gene risk score was not predictive, other polymorphisms that may affect the circadian clock may be important for future studies. Results suggest that chronotype is more predictive of phase timing than amplitude, and may be an important factor in continuing research in vulnerabilities to depression.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Miller, Megan A.mam187@pitt.eduMAM187
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairRoecklein, Kathryn Akroeck@pitt.eduKROECK
Committee MemberManuck, Stephen Bmanuck@pitt.eduMANUCK
Committee MemberHasler, Brant P.haslerbp@upmc.eduBPH6
Committee MemberKamarck, Thomas W.tkam@pitt.eduTKAM
Date: 22 May 2014
Date Type: Publication
Defense Date: 18 December 2013
Approval Date: 22 May 2014
Submission Date: 26 February 2014
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 80
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Psychology
Degree: BS - Bachelor of Science
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: Positive Affect, Circadian Rhythms, Clock Genes
Date Deposited: 22 May 2014 20:01
Last Modified: 19 Dec 2016 14:41


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