Amygdala Volume in Late-Life Depression: Relationship with Age of Onset

Abstract

Depression is common in the elderly population. Although numerous neuroimaging studies have examined depressed elders, there is limited research examining how amygdala volume may be related to depression. A cross-sectional examination of amygdala volume comparing elders with and without a diagnosis of major depressive disorder, and between depressed subjects with early and later initial depression onset. An academic medical center. Ninety-one elderly patients meeting Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, criteria for major depression (54 early-onset depressed and 37 late-onset depressed) and 31 elderly subjects without any psychiatric diagnoses. Amygdala and cerebral volumes were measured using reliable manual tracing methods. In models controlling for age, sex, and cerebral volume, there was a significant difference between diagnostic cohorts in amygdala volume bilaterally (left: F[2, 116] = 16.28, p < 0.0001; right: F[2, 116] = 16.28, p < 0.0001). Using least squares mean group analyses, both early- and late-onset depressed subjects exhibited smaller bilateral amygdala volumes than did the nondepressed cohort (all comparisons p < 0.0001), but the two depressed cohorts did not exhibit a statistically significant difference. Limitations include missing antidepressant treatment data, recall bias, inability to establish a causal relationship between amygdala size and depression given the cross-sectional nature of the design. Depression in later life is associated with smaller amygdala volumes, regardless of age of initial onset of depression.