Midlife depression has long been considered a risk factor for dementia in later life. However, new findings suggest that this relationship is driven by a small cluster of specific symptoms rather than by depression overall. These symptoms are:

• Losing confidence in myself
• Not able to face up to problems
• Not feeling warmth and affection for others
• Feeling nervous and strung-up all the time
• Not satisfied with the way tasks are carried out
• Difficulties concentrating

The researchers say focusing on these six symptoms when treating patients with depression in midlife may reduce their risk of getting dementia later in life, although more research into this link is needed.

The researchers analyzed data from 5,811 middle-aged adults who participated in the Whitehall II study, a British longitudinal cohort initiated in 1985. Midlife depressive symptoms were assessed in 1997–1999, when all participants were dementia-free and middle-aged (age 45-69, average age of 55), using a questionnaire covering 30 common depressive symptoms.

Participants’ health status was then tracked for 25 years through national health registries, with dementia diagnoses recorded up to 2023. During this period, 10.1% developed dementia.

The analyses showed that participants classified as depressed (those reporting five or more symptoms) in midlife had a 27% higher risk of subsequently developing dementia. However, this increased risk was driven entirely by the six specific symptoms in adults under 60. In particular, loss of self-confidence and difficulty coping with problems were each associated with a roughly 50% increased risk of dementia.

In contrast, other depressive symptoms, including sleep problems, suicidal ideation, or low mood, showed no meaningful association with dementia in the long term.

The researchers note that symptoms such as loss of self-confidence, difficulty coping with problems, and poor concentration can lead to reduced social engagement and fewer cognitively stimulating experiences, both of which are important for maintaining cognitive reserve – that is, the brain's ability to cope with damage or disease, enabling normal thinking and function even when the brain is physically affected.

To download the full study, published in The Lancet Psychiatry, click here