Date of Award:

5-2007

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Psychology

Committee Chair(s)

JoAnn Tschanz (committee co-chair) Susan L. Crowley (committee co-chair)

Committee

JoAnn Tschanz

Committee

Susan L. Crowley

Committee

Maria C. Norton

Committee

Ronald G. Munger

Committee

M. Scott DeBerard

Abstract

Research examining a possible relationship between vascular factors and late-life depression in the elderly has produced both evidence for and against a "vascular depression" hypothesis, which posits that late-life depression may have a vascular or neurological etiology. It was hypothesized that a depressive disorder that is primarily the result of structural changes in the brain due to vascular conditions in late-life may be related to increased depression chronicity. We examined data from the Cache County Study on Memory, Health, and Aging to determine whether support for the concept of vascular risk for depression and increased chronicity were present in an epidemiological population of elderly individuals. Participants with dementia at baseline were excluded, and data assessing demographic, vascular conditions and risk factors ( cardiovascular disease, stroke, transient ischemic attack, high cholesterol, hypertension and medically treated diabetes), Activities of Daily Living limitations, and antidepressant treatment were collected. In total, 3,335 study participants were eligible and were examined at 3- and 7- year intervals. Interval diagnostic interview schedule data were examined to determine whether a major depressive episode had occurred, and if so, its duration. In total, 132 participants were identified as experiencing incident major depression, yielding an incidence rate of 6.69 per 1,000 person-years-at-risk. Cox regression models indicated that after controlling for baseline age and activities of daily living limitations, only medically treated diabetes predicted incident depression (p = .051). Analyses utilizing generalized linear mixed models with either a Poisson or gamma distribution indicated no demographic, vascular, or antidepressant treatment variables predicted depression chronicity as measured by the total time in the observation interval depressed, the total number of depressive episodes, or the total time depressed divided by the number of episodes. No statistical trends with regard to the relationship between vascular conditions, risk factors, and depression chronicity were noted. In summary, a link between a vascular risk factor (medically treated diabetes) and incident depression was confirmed, but no relationship between vascular variables and chronicity of incident major depression was detected.

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