Depression and dementia may be more closely linked than previously recognized, according to new research from the University of Nottingham published in eClinicalMedicine.

The study found that depression in both midlife and later life increases dementia risk, with especially strong links seen in older adults. The research also revealed that depression occurring in midlife — during the 40s and 50s — similarly increases the likelihood of developing dementia later. This finding helps clarify longstanding questions about whether early or late-life depression poses a greater risk to brain health.

Lead researcher Jacob Brain, PhD, of the University of Adelaide and Curtin University’s Dementia Centre of Excellence, emphasized the study’s implications for elderly depression and dementia prevention: “Our study shows that depression is linked to an increased risk of dementia in both midlife and late life. This highlights the importance of recognizing and treating depression across the life course, not just for mental health, but also as part of a broader strategy to protect brain health.”

The research team conducted what scientists call an “umbrella review and meta-analysis” — a method that combines results from multiple previous studies to create more reliable overall conclusions. It specifically examined when depression occurred in people’s lives and calculated how much it increased dementia risk at different ages.

A particularly significant finding for elderly depression and dementia understanding is that late-life depression may function as both a risk factor and an early warning sign. “Our findings raise the possibility that depression late in life may not just be a risk factor, but it could also be an early warning sign of dementia beginning to develop,” Brain explained.

The biological connections between depression and dementia involve several complex processes, including chronic inflammation (long-term immune system activation), disruption of stress hormone systems, changes in blood vessels and imbalances in brain chemicals called neurotransmitters.

With more than 57 million people living with dementia worldwide and no cure currently available, identifying and addressing risk factors like depression is a growing public health priority — especially among older adults.