Depression as an early symptom and risk factor of dementia - a narrative review

Depression is a common psychiatric disorder, while dementia represents a growing global health challenge, particularly in aging populations. Although substantial progress has been made in pharmacotherapy, neurodegenerative processes can only be partially slowed, and disease progression cannot be completely halted. Neurodegenerative diseases therefore remain largely incurable, underscoring the importance of early recognition and intervention. This raises an important clinical and conceptual question: does depression represent an early manifestation of dementia, act as a risk factor for its development or both? Understanding these relationships is essential for accurate diagnosis, appropriate treatment, and timely implementation of preventive strategies. This article presents a narrative review of the literature examining the complex relationship between depression and dementia, with a focus on clinical presentation, diagnostic challenges, and neurobiological mechanisms. Neuroimaging techniques such as MRI and PET, and in selected contexts SPECT, support the differential diagnosis of depression and dementia, although limitations in sensitivity and specificity persist. Inflammation has been extensively investigated as a shared pathological mechanism underlying both conditions. Emerging evidence also suggests that anti-amyloid therapies may be associated with improvements in depressive symptoms in selected patient populations, further highlighting overlapping pathophysiological pathways between depression and dementia. Improved understanding of the interplay between depression and dementia may facilitate earlier diagnosis, reduce diagnostic uncertainty, and support the development of more effective preventive and therapeutic strategies.