Antidepressants taken by millions of patients could accelerate memory loss in some patients, a large study suggests.
Swedish scientists found dementia patients taking selective serotonin reuptake inhibitors (SSRIs) suffered a more rapid decline in brain function compared to those not given the drugs.
An estimated 5.4million patients are currently on SSRIs, according to NHS data, making them the most commonly used antidepressant in England.
Antidepressants are also commonly prescribed to dementia patients to combat the mood and behaviour changes they often develop as the condition progresses.
In the study, experts from the Karolinska Institute examined data from nearly 19,000 dementia patients with an average age of 78.
Of these about a fifth were prescribed antidepressants and the majority (65 per cent) were taking SSRIs.
Experts followed patients for an average of four years and compared the results of memory tests, measuring the ability to recall information such as the date, year and lists of words, over time.
Those on the drugs saw their score, measured out of a possible 30 points, decrease by an extra 0.3 points per year compared to those not being treated for depression.
Antidepressants taken by millions of patients in Britain could accelerate dementia, a large study suggests
Swedish scientists found dementia patients taking selective serotonin reuptake inhibitors (SSRIs) suffered a more rapid decline in brain function compared to those not given the drugs. This chart shows declining brain function scores among those taking SSRis (red line) and those not on antidepressants (blue line)
The effect was even greater for SSRIs specifically with scores declining by an extra 0.39 points per year and those on higher doses saw a decline of 0.42 points per year.
The authors said while this difference was large enough to observe the actual impact it would have on patients was clinically ‘uncertain’.
Publishing the results in the journal BMC Medicine, the scientists also found patients on antidepressants had a 7 per cent greater chance of death and 18 per cent greater risk of suffering a fracture.
Those on higher doses of SSRIs were 35 per cent more likely to be diagnosed with severe dementia, an 18 per cent higher chance of death, and a 25 per cent higher of breaking a bone.
However, the experts added that they weren’t able to pin these finding on the drugs themselves.
They said it was possible the poorer health outcomes were a result of the depression the drugs were meant to treat rather than the medication itself.
An additional finding was that a subset of dementia patients, those suffering from frontotemporal dementia, which typically strikes younger people, had a slower rate of disease progression when taking antidepressants.
Professor Tara Spires-Jones, an expert in dementia and president of the British Neuroscience Association, said while the findings were ‘strong’ there were limitations and more research was needed.
But they can also be a sign of dementia — the memory-robbing condition plaguing nearly 1million Brits and 7million Americans
Around 900,000 Britons are currently thought to have the memory-robbing disorder. But University College London scientists estimate this will rise to 1.7 million within two decades as people live longer. It marks a 40 per cent uptick on the previous forecast in 2017
‘People who needed antidepressants may have had more aggressive disease or the depression itself could have been affecting disease progression,’ she said.
‘Previous studies have also reported mixed results, highlighting the need for more research before we have a full understanding of the effects of antidepressant use on dementia progression.’
Richard Oakley, associate director for research and innovation of the Alzheimer’s Society, agreed.
‘This study suggested that antidepressants led to faster rates of memory and thinking decline in people with dementia but it did not rule out the possibility that the changes were due to the presence of depression rather than antidepressant use, so further research is needed to understand the effects of antidepressants,’ he said.
Dr Prasad Nishtala, an expert in life sciences at the University of Bath, said the study also couldn’t explain how antidepressants were accelerating cognitive decline and also called for further research.
‘Because of these limitations, the study’s findings should be interpreted with caution and ideally replicated using other real-world data sources,’ he said.
Dementia affects an estimated one million people in the UK and has a variety of causes, such as Alzheimer’s disease and reduced blood flow to the brain following a stroke, known as vascular dementia.
Recent analysis by the Alzheimer’s Society estimated the overall annual cost of the dementia to the UK is £42billion a year, with families bearing the brunt.
An ageing population means these costs – which include lost earnings of unpaid carers – are set to soar to £90billion in the next 15 years.
Around 944,000 in the UK are thought to be living with dementia while the figure is thought to be around 7million in the US.
Memory problems, thinking and reasoning difficulties and language problems are common early symptoms of the condition, which then worsen over time.
A separate Alzheimer’s Research UK analysis found 74,261 people died from dementia in 2022 compared with 69,178 a year earlier, making it the country’s biggest killer.
