Depression and Brain-Derived Neurotrophic Factor Levels in Alzheimer’s Disease

Background: Depression is often viewed as a risk factor for the development of Alzheimer’s disease (AD), however little is known regarding the underlying biological mechanisms linking these two diseases. Brain-derived neurotrophic factor (BDNF) has been linked to both cognitive impairment and depression in past research; however few studies have examined this relation in a sample of Alzheimer’s patients. The present study sought to address this gap in the literature by examining the relation between serum BDNF levels and depression assessed by the Geriatric Depression Scale (GDS) in a group of patients diagnosed with probable Alzheimer’s disease. Methods: Participants included 169 individuals diagnosed with Probable AD enrolled in the TARC Longitudinal Research Cohort with available BDNF levels and GDS scores. The participants were divided into Depressed (N = 20) and Not Depressed (N = 149) based on GDS scores. Results: BDNF levels significantly predicted level (High vs. Low) of depression (β = 0.066, SE = 0.031, p = 0.034). BDNF levels for the Depressed group were significantly higher than those observed in the Not Depressed group (p > 0.036). Conclusions: These findings suggest that an upregulation of BDNF possibly exists among depressed AD patients as a response to the chronic inflammatory processes that occur in depression. This upregulation of BDNF appears to persist at least into early stages of Alzheimer’s.