People taking antidepressants in middle or old age could have triple the risk of developing dementia, a study has found.
Antidepressants may damage or kill crucial nerve cells in the brain, researchers claimed in a study of more than 71,000 people.
Rates of dementia were found to be 3.4 times higher among people who took the depression drugs after the age of 60.
The findings should encourage people and doctors to weigh up the risks and benefits of antidepressant treatment, the researchers said.
But one expert warned scientists are increasingly turning to believe depression may actually be an early symptom of dementia and a consequence of years of changes in the brain.
Others said there is no evidence the pills cause the brain disease – only that there is a link between the conditions – and depression treatment should not be avoided.Researchers from Israel, Sweden and New York studied a group of 71,515 real patients in Israel between 2013 and 2017.
All people in the study were over the age of 60 by 2012 and had not yet been diagnosed with dementia.
They were split into groups of those who had taken antidepressants during the decade (3,688 people) and those who hadn’t (67,827).In the antidepressant-taking group, 11 per cent of people developed dementia before the end of the study – a total of 407 people.
While in the group which didn’t take the pills, that rate was just 2.6 per cent (1,769 people).
When the results were adjusted to make them fair, the dementia risk of people in the antidepressant group was 3.4 times higher.
The overall rate of dementia is around five to six per cent, meaning people have a one in 20 chance of getting it – but some groups are at higher risk than others.
‘Our study results indicate that antidepressant exposure in old age may increase the risk of dementia,’ said the researchers, led by Dr Stephen Levine of the University of Haifa in Israel.They reported they could not draw more specific results about types of drugs, though only included people who were treated with a single type of medicine.
In the paper they added: ‘Clinicians, caregivers and patients may wish to consider this potential negative consequence of antidepressant exposure with the objective of balancing the adverse events and symptomatic benefits of… antidepressant medication in old age’.
The research suggested the drugs may cause nerve damage, stop the growth of nerve cells, or be toxic to normal cells in the brain.
However, one expert said the finding should not be used to stop people from taking antidepressants, and the link may actually go the other way.
Professor Rob Howard, an expert in old age psychiatry at University College London, told MailOnline: ‘It used to be thought that depression was a risk factor for dementia but when you look at the longer term, over 20 years before someone develops dementia, that isn’t the case.
‘It seems to be only proximal to diagnosis of dementia and people with depression have probably had progressive [brain damage] for a number of years.
‘We’re increasingly seeing depression as a [sign] of Alzheimer’s-type pathology in the brain.’
Professor Howard added research must be presented carefully to avoid ‘terrifying’ people who are most in need of antidepressant treatment.
Professor Wendy Burn, President of the Royal College of Psychiatrists, added: ‘There is no evidence that antidepressants cause dementia.
‘There is an association as people with dementia are more likely to be depressed and therefore more likely to be on antidepressants.’
Dr James Pickett, head of research at the Alzheimer’s Society, said: ‘This study didn’t examine the dose, the effects of different types of antidepressants, and how long people were taking them for, which are important questions to guide treatment.
‘It is challenging to distinguish between depression and dementia in its early stages, and it’s possible people with dementia were misdiagnosed and prescribed an antidepressant.
‘However, although this study is not conclusive, it does support research we’ve funded, which showed some types of antidepressants may have a small increased risk of dementia associated with them.’
And Dr Laura Phipps from Alzheimer’s Research UK added: ‘Some previous studies have linked certain types of antidepressant to a higher dementia risk due to their impact on levels of chemical messengers in the brain.
‘However, depression can also be an early symptom of dementia, so using antidepressants may reflect these early brain changes.
‘Many treatments that bring benefits also carry side effects. While doctors must weigh up benefit and harm when prescribing any medication, further research into the impact of medication on dementia risk will help better inform those making such decisions.’
The Israel researchers published their study in the American Journal of Geriatric Psychiatry.