DuPont, Caitlin
(2019)
THE ROLE OF ENVIRONMENTAL LIGHT EXPOSURE AND CIRCADIAN TIMING IN SEASONAL AFFECTIVE DISORDER.
Master's Thesis, University of Pittsburgh.
(Unpublished)
This is the latest version of this item.
Abstract
Background: Individuals with seasonal affective disorder (SAD) experience depressive episodes in the winter that remit in the summer. The phase shift hypothesis of SAD suggests that a later sunrise in winter delays circadian phase that then leads to depression. As the circadian system is optimally sensitive to blue wavelengths, blue light exposure may be particularly important for SAD. Thus, the current study aims to investigate whether circadian phase mediates the association between blue light exposure and depressive symptoms in SAD. Methods: Adults (N = 90; 81% women) with varying degrees of seasonality were recruited in winter. Light was measured by an actigraphy watch with a photodiode. Depressive symptoms were measured by a clinical interview while circadian phase was estimated by both self-reported sleep-wake times and melatonin onset. Results: A longer duration and later timing of blue light exposure were both associated with delayed melatonin onset. Neither circadian phase, nor blue light exposure was associated with depressive symptoms in the full sample. When women were analyzed separately, a relatively advanced circadian phase mediated the relationship between reduced blue light exposure centered in the afternoon and greater depressive symptoms. Discussion: Our results contrast previous reports that a relative delay in circadian phase is associated with greater depressive symptoms. In the full sample, this association was not present and when the data were analyzed separately for women, more advanced phase was associated with greater depression. Thus, future studies recruiting more men are necessary to determine whether gender influences the relationship between phase and depressive symptoms in SAD.
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Details
| Item Type: |
University of Pittsburgh ETD
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| Status: |
Unpublished |
| Creators/Authors: |
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| ETD Committee: |
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| Date: |
19 June 2019 |
| Date Type: |
Publication |
| Defense Date: |
1 December 2017 |
| Approval Date: |
19 June 2019 |
| Submission Date: |
22 January 2019 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
112 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Dietrich School of Arts and Sciences > Psychology |
| Degree: |
MS - Master of Science |
| Thesis Type: |
Master's Thesis |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
Circadian rhythms, depression, light exposure |
| Date Deposited: |
19 Jun 2019 20:10 |
| Last Modified: |
19 Jun 2019 20:10 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/36928 |
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THE ROLE OF ENVIRONMENTAL LIGHT EXPOSURE AND CIRCADIAN TIMING IN SEASONAL AFFECTIVE DISORDER. (deposited 19 Jun 2019 20:10)
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