Dr Etuini Ma'u, from Auckland University's department of psychological medicine. Photo: Supplied/Pasifika Medical Association
Depression and anxiety can lead to a significantly higher risk of dementia later in life, according to new research out of Auckland University.
In a briefing from the Public Health Communication Centre, Dr Etuini Ma'u and co-authors from the university's Department of Psychological Medicine report finding common mental health conditions, such as depression and anxiety, substantially increase a person's risk of developing dementia.
Using data from the New Zealand Health Survey, the researchers followed adults who had reported a diagnosis of depression, anxiety or bipolar disorder to assess their future risk of dementia.
The results showed anxiety was linked to a 30 percent higher risk of dementia and depression increased the risk by 40 percent.
Bipolar disorder was associated with nearly a threefold increase, psychological distress more than doubled dementia risk and severe distress nearly tripled it.
Ma'u, a senior lecturer and consultant psychiatrist, said depression had for a long time been considered a risk factor for dementia, but previously there had not been enough strong evidence to link anxiety, biopolar or psychotic disorders.
This study had aimed to "add to that evidence base", Ma'u said.
It built on some existing studies - one from 2022, also from the University of Auckland, had found depression elevated dementia risk by three to four times.
But that study had looked at people in hospital. "You've kind of self-selected a really severe group of mental disorders and we know that, in a New Zealand setting, most people with depression and anxiety are managed in the community."
Ma'u said this research wanted to study a more representative risk for the general population.
The Public Health Communication Centre briefing noted anxiety and depression symptoms were on the rise - between 2016 and 2023, the number of New Zealanders reporting symptoms rose by more than half.
However, the number of people reporting they could not get the mental health support they needed also rose by 50 percent.
As New Zealand's population aged, dementia rates were projected to double by 2050, from an estimated 83,000 cases today to 167,000 by 2050.
Ma'u said a "life course" approach was needed - starting in childhood - to reduce the effects of anxiety and depression.
"We talk about dementia as being something that affects older people, but what we know is that actually, the cumulative and incremental damage happens to our brain over the course of a lifetime eventually overwhelm our brains' ability to cope, and that's a dementia that we see.
"We need to be looking right back to childhood."
But change could not come from an individual level, he said.
"Effective interventions are going to have to come from a policy and legislative level, so that we can address some of these broader determinants of health."
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