The pathophysiologic basis for late-life depression: Imaging studies of the aging brain
Available evidence on late-life depression does not support the concept that psychological or social factors are the sole contributors. Several studies suggest that there is a lower genetic loading to late-onset depression; thus, late-life depression may be attributable to other factors, such as cerebrovascular changes. With magnetic resonance imaging (MRI), researchers can now examine subtle cerebrovascular changes in the brain. The aging process and related medical illnesses are associated with leukoencephalopathy, which includes periventricular hyperintensities and deep white-matter hyperintensities (DWMH), also associated with carotid atherosclerosis; both characteristics are detectable on MRI scans. Brain MRI studies of older depressed patients suggest that cerebrovascular pathology plays a major role in etiology, and imaging studies of stroke patients can clarify neuroanatomic substrates for the emergence of depression. There is also a correlation between the severity of DWMH and the severity of myocardial infarction. Other possible etiologies for late-life depression include endocrine disorders and the phenotypic apolipoprotein E alleles ε4/4 and ε4/3.
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