Depression is a common mental health condition that occurs throughout the lifespan, while dementia is prevalent in late life. Research suggests a link between depression and dementia, with earlier-life depression showing a stronger association with increased dementia risk. Late-life depression is more controversial, but most studies support a connection, though the nature of this relationship remains unclear. Biological mechanisms linking depression to dementia include vascular disease, glucocorticoid alterations, hippocampal atrophy, amyloid plaque accumulation, inflammation, and nerve growth factor deficits. Treatment strategies for depression may influence dementia risk by targeting these pathways. Understanding the relationship between depression and dementia is crucial for developing effective prevention and treatment strategies, especially given the projected increase in dementia cases. Studies indicate that depression, particularly in earlier life, may be a risk factor or early symptom of dementia. The mechanisms underlying this link involve vascular disease, cortisol-hippocampal pathways, amyloid plaque formation, and inflammatory changes. Treatment approaches for depression, including pharmacological and behavioral interventions, may help reduce dementia risk. However, the effectiveness of these treatments in preventing or slowing dementia progression is still under investigation. The review highlights the need for further research to clarify the relationship between depression and dementia, focusing on potential mechanisms and the importance of early intervention. The aging population and rising dementia rates underscore the urgency of understanding and addressing the link between depression and dementia.Depression is a common mental health condition that occurs throughout the lifespan, while dementia is prevalent in late life. Research suggests a link between depression and dementia, with earlier-life depression showing a stronger association with increased dementia risk. Late-life depression is more controversial, but most studies support a connection, though the nature of this relationship remains unclear. Biological mechanisms linking depression to dementia include vascular disease, glucocorticoid alterations, hippocampal atrophy, amyloid plaque accumulation, inflammation, and nerve growth factor deficits. Treatment strategies for depression may influence dementia risk by targeting these pathways. Understanding the relationship between depression and dementia is crucial for developing effective prevention and treatment strategies, especially given the projected increase in dementia cases. Studies indicate that depression, particularly in earlier life, may be a risk factor or early symptom of dementia. The mechanisms underlying this link involve vascular disease, cortisol-hippocampal pathways, amyloid plaque formation, and inflammatory changes. Treatment approaches for depression, including pharmacological and behavioral interventions, may help reduce dementia risk. However, the effectiveness of these treatments in preventing or slowing dementia progression is still under investigation. The review highlights the need for further research to clarify the relationship between depression and dementia, focusing on potential mechanisms and the importance of early intervention. The aging population and rising dementia rates underscore the urgency of understanding and addressing the link between depression and dementia.