The drugs, used to treat clinical depression as well as other conditions such as OCD and PTSD, are taken by millions of Britons.
Now, a new study has found that the drug could increase the risk of heart disease.
However, experts have warned people not to stop taking the drugs.
Researchers at the University of Bristol found “related associations” between taking the pills for ten years and increased heart disease, death from cardiovascular disease and earlier death from any cause.
Experts said they couldn’t be sure it wasn’t depression itself increasing the risks of heart problems, which was echoed by other experts who said people shouldn’t be alarmed by the findings.
The scientists looked at eight antidepressants, including the selective serotonin reuptake inhibitors (SSRIs) citalopram, sertraline, fluoxetine and paroxetine.
They also looked at four other antidepressants: mirtazapine, venlafaxine, duloxetine and trazodone.
Published in the British Journal of Psychiatry Open, the data included more than 200,000 people from the UK Biobank aged 40 to 69 whose records could be examined.
SSRIs were the most commonly prescribed antidepressant, with another 80% of the group taking one of the medications.
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People taking antidepressants were compared with those not taking medication.
After 10 years, those taking SSRIs had a 34% increased risk of heart disease, a nearly doubled risk of cardiovascular death.
They were also 73% more likely to die from any cause.
For the other antidepressants, all risks were around double.
The researchers said: “Antidepressants, and especially SSRIs, may have a good short-term safety profile, but are associated with adverse long-term outcomes.
“This is important because most of the substantial increase in prescribing over the past 20 years or more is in long-term repeat prescribing.”
The study also found that antidepressants, and SSRIs in particular, were associated with a 23 to 32 percent lower risk of developing high blood pressure and diabetes, although more research is needed.
Dr Narinder Bansal, the study’s lead author, said people should not stop taking their medication suddenly and should talk to their GP if they are concerned.
“Although we took into account a wide range of pre-existing risk factors for cardiovascular disease, including those linked to depression, such as excess weight, smoking and low physical activity, it is difficult to fully control the effects of depression in this type of study.
“This is partly because there is considerable variability in the recording of depression severity in primary care,” he said.
He adds: “This is important because many people taking antidepressants such as mirtazapine, venlafaxine, duloxetine and trazodone can have more severe depression.
“This makes it difficult to completely separate the effects of depression from the effects of medication
“Further research is needed to assess whether the associations we’ve seen are really due to drugs and, if so, why that might be,” he said.
Experts said doctors need to be aware that prescribing antidepressants long-term “may not be free of harm”.
They called for “proactive cardiovascular monitoring” in patients taking long-term antidepressants, “given that both have been associated with increased risks.”
Glyn Lewis, professor of psychiatric epidemiology at University College London (UCL), said people should not be “alarmed or worried” by the findings or stop taking their medication.
He said the study could not conclude whether depression increased health risks or the use of antidepressants.
“There is a lot of evidence, from other research, that depression is associated with increased cardiovascular disease,” he said.
“Clearly there are behavioral things (associated with depression) where people might not take care of themselves as well.
“There may also be hormonal and metabolic changes that can increase the risk of long-term physical ailments,” he added.
Professor Glyn said experts should be aware of the potential long-term effects of antidepressants as they are a commonly used drug, but added: “We wouldn’t want people to stop their medication on the basis of ‘this kind of result.
“These results alone should not make people think they should stop their antidepressants. This type of study is not strong enough to draw this type of conclusion.”
Professor Martin Marshall, president of the Royal College of GPs, said: “Existing evidence shows that antidepressants can be an effective treatment for the distressing and often debilitating symptoms of anxiety and depression when used appropriately.
“GPs are highly trained to have open and sensitive conversations with their patients and, when discussing mental health issues, will consider a range of treatment options based on the patient’s unique needs.
“If antidepressants are prescribed, it will generally be at the lowest dose and for the shortest amount of time.
“This is an interesting study, and as the authors have pointed out, more research is needed in this area.
“However, it is very important that patients do not stop taking their prescribed antidepressants as a result of this research, but if they are concerned they should discuss this at their next medication review,” he explained.
Professor Carmine Pariante, from the Royal College of Psychiatrists, said: ‘Long-term use of antidepressants should only be considered for people who have recurrent depression and repeated severe relapses after stopping antidepressants.
“For these patients, the beneficial effects of continued antidepressant use are more likely to balance the potential risks.”
NHS figures released in July showed that 8.3 million patients were prescribed antidepressants in 2021/22 in England, up 6% from 7.9 million the previous year.
Meanwhile, The Sun revealed that more than one million anti-depressant prescriptions were handed out to teenagers last year.
In 2019, research that analyzed around 1,000 existing studies, published in JAMA Psychiatry, concluded that antidepressants are generally safe.