Emerging research shows link between depression in younger adults and dementia
SINGAPORE – Depression in people above the age of 60 is associated with an increased risk of dementia, and may sometimes be an early sign of cognitive decline.
Now, emerging research has highlighted a significant link between depression diagnosed in young and middle-aged adults and an increased risk of dementia later on.
A 2023 study published in US-based medical journal Jama Neurology analysed data from over 1.4 million Danish citizens and identified whether they had been diagnosed with depression. They were then followed from 1997 to 2018 to see who developed dementia later in life.
Those diagnosed with depression, including young and middle-aged adults aged 18 to 59, were more than twice as likely to be diagnosed with dementia later in life compared with those without depression. This is according to an analysis by researchers at the Perelman School of Medicine at the University of Pennsylvania and Aarhus University in Denmark.
The link highlights the importance of addressing mental health to protect long-term brain function.
Depression and dementia are common conditions in Singapore.
According to the SingHealth website, an estimated 5.8 per cent of the population suffer from depression. And Singaporeans deemed mental health as the biggest health problem the country faced in 2023, above cancer and stress, according to the World Mental Health Day 2023 report by market research firm Ipsos.
Dementia advocate Emily Ong says with growing awareness and emphasis on mental health and well-being, it is crucial to explore the potential long-term impacts on cognitive health in Singapore’s ageing population.
According to the Institute of Mental Health’s Well-being of the Singapore Elderly study released on Aug 28, the number of seniors with dementia rose from 51,934 in 2013 to 73,918 in 2023 – because of an increase in the adult population here.
But the prevalence of dementia among older adults aged 60 and above here had dropped to 8.8 per cent, down from 10 per cent in 2013.
The study also found that those with a history of depression – it did not state how old they were – were nearly three times more likely to have dementia.
Ms Ong, who was diagnosed with young-onset dementia when she was 50, has seen young and middle-aged adults with depressive symptoms who develop dementia later in life.
Her relative, for instance, was diagnosed with depression in her 30s and is starting to experience cognitive decline like memory issues and reduced alertness. Ms Ong’s relative is in her 50s now and still taking medication for depression.
Dr Seng Kok Han, a consultant psychiatrist at Nobel Psychological Wellness Centre, frequently sees patients who have both depression and dementia.
For example, his patient, Mr A, was diagnosed with depression in his late 40s and has been battling chronic depression for many years. He struggled to stay consistent with his antidepressant medication and follow-up care.
By the time he reached his early 70s, Mr A started experiencing cognitive difficulties, such as forgetting appointments and having trouble with daily tasks. He was eventually diagnosed with dementia.
“Even after stabilising his depression, his cognitive deficits persisted. In his case, the long history of untreated or poorly managed depression likely played a significant role in his cognitive decline,” says Dr Seng.
What do dementia and depression have in common?
Dementia is a general term for the ongoing decline of cognitive functioning to an extent that it interferes with a person’s daily life and activities. Depression is a mood disorder that causes a persistent feeling of sadness and loss of interest. It affects how you feel, think and behave, and can lead to emotional and physical problems.
Dr Annabelle Chow, principal clinical psychologist at Annabelle Psychology, says there has been evidence in recent years which show that depression in early adulthood is associated with an increased risk of dementia.
However, the mechanisms involved are complex, she says, with no single process being able to fully explain this connection.
It is clear, however, that both depression and dementia cause increased neurodegeneration and reduced neuronal repair, says Dr Chow.
This means that in both conditions, there is a faster or greater loss of brain cells, leading to a decline in brain function over time, and the brain’s ability to fix or heal its nerve cells is weakened or slowed down.
Chronic depression can speed up changes in the brain that may lead to dementia through at least two physical processes, says Dr Chow.
The first involves changes in blood vessels in the brain, mainly in the form of a condition called leukoaraiosis, which damages the brain’s white matter. This has been identified as a risk factor for dementia, she notes.
The other is through excessive release of cortisol, a stress hormone which, in turn, damages the hippocampus – a part of the brain that is crucial for forming and storing memories.
“Chronic elevation of cortisol can damage brain structures that are important for memory and cognitive function. This can lead to the shrinking in brain structure and function, including reduced hippocampal volume, and contribute to a person developing dementia later in life,” says Dr Chow.
In addition, depression can result in a person isolating himself or herself. The reduced activity or interaction increases the risk of developing dementia, says Dr Chow.
In her practice, she does see adults with depression who are concerned about their cognitive function.
Certain subtypes of depression in particular, like vascular depression, have been linked to an increased risk of developing dementia, says Dr Seng.
“This association is thought to arise because both conditions share common vascular risk factors, such as hypertension, diabetes and atherosclerosis (build-up of fats, cholesterol and other substances in and on the artery walls). These risk factors can lead to reduced blood flow and damage to brain tissues, which contribute to cognitive decline and the development of dementia,” he adds.
Vascular depression is a type of depression in older adults, typically over the age of 60. It is associated with reduced blood flow and vascular changes in the brain, such as small vessel disease, which can impair mood regulation.
Studies have also shown that people who experience recurrent or severe depression are at higher risk of developing dementia.
Dr Chow says this relationship may be explained by research related to the brain, which suggests that prolonged depression can lead to damage in the hippocampus.
“Over time, this damage, along with the cognitive impairments associated with chronic depression, like reduced concentration and slowed thinking, may contribute to the development of dementia,” she says.
Depression, even in its milder forms, has been linked to an increased risk of developing dementia.
“Even subsyndromal depression, which refers to the presence of depressive symptoms that do not meet the full criteria for a depressive disorder, can increase the risk of dementia,” adds Dr Chow.
Distinguishing depression and dementia symptoms
Identifying whether depressive symptoms might be related to dementia can be challenging because the symptoms of both conditions often overlap, says Dr Sanveen Kang, clinical psychologist and founder at Psych Connect.
However, there are some signs which may differentiate the two.
In depression, cognitive issues such as memory problems, difficulty concentrating and decision-making difficulties are often reversible with appropriate treatment, says Dr Kang.
However, cognitive decline in dementia is progressive and typically irreversible.
“People with dementia may not recognise or be aware of their cognitive deficits, and they might fill in memory gaps with fabricated or distorted information, rather than express concern,” notes Dr Kang.
Those with depression typically respond well to antidepressant medications together with psychotherapy, and a person’s cognitive symptoms may improve significantly once the depression is treated, she says.
However, if the depression is brought on by dementia, a person’s mood symptoms may get better with treatment, but his or her cognitive decline will continue to progress, adds Dr Kang.
A lack of improvement in cognitive function despite successful treatment of depressive symptoms could indicate underlying dementia, she says.
Early treatment for depression can reduce risk of cognitive decline
Depression can increase the risk of cognitive decline, but addressing it promptly can reduce this risk, notes Dr Seng.
“As depression is associated with increased inflammation, which can contribute to brain changes linked to dementia, treating the condition may reduce inflammation, potentially lowering the risk of dementia,” says Dr Kang.
In addition, certain antidepressant medications, like selective serotonin reuptake inhibitors, may help protect against brain changes associated with depression and dementia, she adds.
Some studies suggest that these medications can improve neuroplasticity and reduce hippocampal atrophy, which are crucial for cognitive function, notes Dr Kang.
Seeking help for depression is a sign of strength, not weakness, says Dr Seng.
“Your general practitioner can be an excellent first point of contact. He or she can assess your symptoms and refer you to a psychiatrist, psychologist or counsellor if needed,” he adds.
Ms Ong, who is a board member of Alzheimer’s Disease International, says: “We need to continually create a culture that talks about mental health. Mental health and brain health are very important, but there is a lack of awareness of their links.”
Helplines
Mental well-being
- Institute of Mental Health’s Mental Health Helpline: 6389-2222 (24 hours)
- Samaritans of Singapore: 1-767 (24 hours) / 9151-1767 (24 hours CareText via WhatsApp)
- Singapore Association for Mental Health: 1800-283-7019
- Silver Ribbon Singapore: 6386-1928
- Tinkle Friend: 1800-274-4788
- Chat, Centre of Excellence for Youth Mental Health: 6493-6500/1
- Women’s Helpline (Aware): 1800-777-5555 (weekdays, 10am to 6pm)
Counselling
- Touchline (Counselling): 1800-377-2252
- Touch Care Line (for caregivers): 6804-6555
- Care Corner Counselling Centre: 6353-1180
- Counselling and Care Centre: 6536-6366
- We Care Community Services: 3165-8017
Online resources
- mindline.sg
- eC2.sg
- www.tinklefriend.sg
- www.chat.mentalhealth.sg
- carey.carecorner.org.sg (for those aged 13 to 25)
- limitless.sg/talk (for those aged 12 to 25)
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