Depression may increase dementia risk in both midlife and late life

A new study has found that depression is linked to an increased risk of dementia in both mid and later life.

The new research, which is published in eClinicalMedicine, was led by Jacob Brain and Maha Alshahrani from the Institute of Mental Health and School of Medicine at the University of Nottingham, University of Adelaide and the Dementia Centre of Excellence at Curtin University in Australia.

Our study shows that depression is linked to an increased risk of dementia in both midlife and late life. This highlights the importance of recognising and treating depression across the life course, not just for mental health, but also as part of a broader strategy to protect brain health. Public health efforts need to place greater emphasis on preventative brain health, including scaling up access to effective mental health care."

Mr. Jacob Brain, Institute of Mental Health and School of Medicine, University of Nottingham

Dementia affects over 57 million people globally. There is currently no cure, so identifying and treating the factors to reduce the risk, such as depression, is an important public health priority.

The potential links between depression and dementia are complex and may include chronic inflammation, hypothalamic-pituitary-adrenal axis dysregulation, vascular changes, alterations to neurotrophic factors and neurotransmitter imbalances. Shared genetic and behavioural related changes may also increase the risks.

Previous studies have shown that people with depression are more likely to develop dementia later in life, but there's been a lot of debate about when depression matters most, whether it's depression that starts in midlife - in your 40s or 50s, or depression that appears later in life - in your 60s or beyond.

This new research brings together all the existing evidence and adds new analysis to examine this timing in more detail.

"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. By clarifying this timing, our work helps guide future research, treatment, and prevention strategies," says Mr. Brain.

The team carried out an umbrella review and meta-analysis. They firstly gathered and reviewed all the best available data from systematic reviews with meta-analyses (a statistical method that combines results from multiple studies to provide a more reliable overall estimate), that had already looked at the link between depression and dementia.

They then went a step further by extracting and re-analysing data from the individual studies within those reviews, plus they added in newer studies that were missed in the earlier work.

Mr. Brain adds: "We specifically focused on the timing of when depression was measured, whether it was measured in midlife or in later life, and calculated how much it increased the risk of developing dementia. This essentially allowed us to provide a more accurate and up-to-date picture of how depression at different life stages is linked to dementia risk."