Depression doubles dementia risk: Study

A four-decade study of more than 1.4 million adults has revealed the risk of dementia jumps a staggering 2.41 times for those diagnosed with depression.  
 
Published in the JAMA Neurology, Danish researchers found the association between the two conditions persists irrelevant of whether depression is diagnosed in early, middle, or late life.
 
The association remained the same even when a patient was prescribed an antidepressant in the six months before or after their diagnosis.
 
‘Our results therefore suggest that depression is not only an early symptom of dementia, but also that depression is associated with an increase in dementia risk,’ the report said.
 
GP and coordinator of the Dementia Subgroup of RACGP Specific Interests Aged Care, Dr Stephanie Daly said the link between the two conditions is well-established.
 
‘It makes sense that some of the factors that lead to dementia pathology are related to the brain undergoing stress, if you like, and depression over years can be a stressor on the brain,’ she told newsGP.
 
The study found the risk of dementia was greater for males living with depression but said this could be attributed to men being less likely to seek healthcare, leading to a more severe disease at the time of diagnosis.

Of the more than 400,000 Australians living with dementia in 2023, it is estimated up to one third  experience depressive symptoms.
 
Those living in long-term residential care are particularly at risk of mental illness.
 
Dr Daly said support should be given to patients with depression at a young age to reduce the impact when they are older.
 
‘The more we can do for risk factor management in midlife the better,’ she said.
 
‘It also helps to open up conversations about dementia in early and midlife which helps with destigmatising the condition.’
 
But she said it is important for GPs to remember depression and dementia can, and often do, coexist at any stage of someone’s illness.
 
‘As part of an assessment of someone’s cognition, we would routinely assess for pre-existing mood disorders such as depression, so sometimes a diagnosis will be made in the individual with pre-existing depression,’ Dr Daly said.
 
‘It is also true that an individual may experience depression alongside their diagnosis of dementia, as the changes that occur can lead to social isolation, loss of confidence and motivation, all of which can adversely affect mood.’
 
The study’s authors hope their findings will help create more effective treatments for both conditions in the future.
 
‘These results may motivate ongoing research focused on the complex and time-varying association between treatment and dementia, particularly when direct measures of disease burden and depression severity are available,’ they said.
 
They also added that further study is needed to examine additional factors increasing dementia risk including family history, physical activity, diet, reproductive history, and social connectedness.
 
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