Pathophysiology of Neurodegeneration in Late-life Depression (AV45+THK)

Late-life depression has been frequently associated with cognitive impairment. Several meta-analyses consistently suggested that a history of depression approximately doubles an individual's risk for developing dementia later in life. Neurodegeneration may play an important component in late-life depression. The pathophysiology behind the link between late-life depression and the subsequent development of dementia largely remains unclear, and should be heterogeneous. This highlights the need to identify specific neurodegenerative pathways involved in late-life depression, which will facilitate research on mechanisms and new treatments in the future. The recently published the National Institute on Aging and the Alzheimer Association (NIA-AA) criteria might provide new insights and frameworks to explore the patterns of neurodegenerative process in elderly depressed patients and to categorize them into different biomarker-based groups. In the present project, the investigators will recruit 40 patients with lifetime major depressive disorder, and 20 non-depressed cognitively normal comparison subjects. Alzheimer's disease pathology (A) was determined by measuring Aβ deposition by F-18 AV-45 PET, and neurodegeneration (N) was established by measuring hippocampal volume using MRI. Individuals were categorised as A-N-, A+N-, A+N+, or suspected non-Alzheimer's disease pathophysiology (A-N+, SNAP). All subjects will further undergo F-18-THK-5351 image study to detect underlying tau pathology. By doing this, the investigators will elucidate the neurodegenerative pathophysiology behind the link between depressive disorder and the subsequent development of dementia.