The Relationship between Subsyndromal Symptomatic Depression and Cognitive Dysfunction
Subsyndromal Symptomatic Depression (SSD), or subthreshold depression, affects roughly 15% of community-dwelling older adults and puts them at increased risk for developing Major Depressive Disorder (MDD), which represents a risk factor for Alzheimer’s Disease (AD) and may expedite disease progression. While the relationship between MDD and AD has been well established, the interaction between SSD and cognitive functioning has not been explored in depth. Further, clinicians have long postulated that depression is not a monolithic disorder but rather a group of disorders which are heterogeneous in onset, symptoms, course, and treatment. One hundred and six participants, 65 and older were recruited as part of the Adventist Health Study-2 Cognition and Neuroimaging Substudy and underwent comprehensive neuropsychological testing. Results of an independent samples t-test revealed that individuals who met criteria for SSD performed significantly worse in the immediate recall over five learning trials on the Rey Auditory Verbal Learning Test (RAVLT) than individuals who did not report depressive symptomatology. Further, a hierarchical regression analysis evidenced that depressive symptoms categorized as “hopelessness”, “dysphoric mood”, and “cognitive impairment” were significant predictors of global cognitive functioning within our SSD sample. These findings suggest that SSD— specifically when symptoms are related to “hopelessness”, “dysphoric mood”, and “cognitive impairment”—has a significant impact on cognition. Future research should utilize a longitudinal study design that examines conversion rates of SSD to MCI/dementia to conclude that SSD represents a clinical marker of dementia. If identified as a viable clinical marker, early detection and treatment of SSD could potentially prevent worsening of depression symptoms as well as delay—or even curb— the manifestation of MCI/Dementia in later life.
Geropsychology, Depression--In old age; Alzheimer’s Disease
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