Almost nine million people in England – roughly one in six of the population – were prescribed an antidepressant last year.

The pills have long been hailed as life-changing treatments for depression and anxiety, helping to relieve symptoms by boosting the ‘feel good’ brain chemical serotonin.

But what was once more commonly a treatment measured in months is increasingly stretching far beyond that.

Around half of those prescribed antidepressants have been taking them for more than two years, official figures show, while one quarter – equivalent to around two million people – have used them for more than five years.

Many argue that is a good thing. Severe depression, which affects about one in 20 adults, is a serious illness, and some research has found long-term antidepressant use is a vital tool in reducing the risk of relapse and suicide.

The drugs can also be used to treat sleep problems, post-traumatic stress disorder and chronic pain.

But the challenge for patients – and for the doctors handing out the medication – is a stark fact: little is known about the effects of staying on such drugs for years.

Some experts are now warning the benefits of extended antidepressant use are being overstated. And – more significantly – they point to studies that suggest they may be linked to serious side effects.

Almost nine million people in England – roughly one in six of the population – were prescribed an antidepressant last year

Those effects are wide-ranging, and include heart problems – including sudden cardiac death – weight gain, weakened bones and fractures, sexual dysfunction, type 2 diabetes, and even dementia and cognitive decline. A direct link between these conditions and antidepressants has not been definitively proven. But, increasingly, experts believe that the emerging evidence is enough to recommend that patients should not take the pills for any longer than is strictly necessary – and certainly not indefinitely.

One of them is Professor Joanna Moncrieff, a psychiatrist at University College London and a vocal critic of psychiatric medication. She has recently been involved in a study which reviewed the research on the side effects associated with the long-term use of antidepressants.

That study, which is yet to be published, focused on people taking the pills for more than a year and found a link to type 2 diabetes, weight gain, and falls and fractures in older people.

‘We certainly can’t say that long-term antidepressants are safe or harmless,’ Prof Moncrieff says, ‘because we have not done enough research to know that. The main finding of our review is that the evidence for effects of long-term antidepressant treatment is very poor.

‘There are few studies and they are mostly low quality. We haven’t investigated this issue properly, and that should be a cause for concern, especially since there are so many long-term users.

‘Getting into a pattern of using antidepressants for shorter periods than we currently do would reduce the harm they cause and the morbidity burden associated with them considerably.’

Psychiatrist Dr Sameer Jauhar, from Imperial College London, adds: ‘We now know, from several studies, that different antidepressants have different long-term effects – particularly on the heart – and that should be built into the decisions being made by doctors when they prescribe to patients.’

At the moment, official guidance from medicines body the National Institute for Health and Care Excellence (NICE) recommends people should consider stopping antidepressants after at least six months of significant improvement. For depression which recurs, people can continue to take the tablets for ‘two years or longer’.

Professor Joanna Moncrieff, a psychiatrist at University College London and a vocal critic of psychiatric medication

But few are warned of any additional risks involved in doing so. Partly that is because the research is difficult to unpick.

People with depression are already at greater risk of heart disease, stroke, type 2 diabetes, obesity and dementia, because symptoms such as lethargy and a lack of motivation can make it harder to maintain a healthy diet and lifestyle.

Scientists also believe that depression may contribute to harmful inflammation throughout the body and brain, which is thought to play a role in a range of chronic diseases.

That means teasing out whether a specific side effect is caused by an antidepressant, or as an indirect effect of depression itself, is not straightforward.

Professor Glyn Lewis, Professor of Epidemiological Psychiatry at University College London, says many of the studies linking antidepressants to long-term health problems are observational – they follow large groups of people over time – meaning they can identify associations but cannot prove that the drugs themselves are responsible. However he adds: ‘It’s clearly something we have to take seriously.’

Professor of psychiatry Dr David Healy, who has long researched the side effects of antidepressants, is convinced the harms are biologically plausible.

‘Serotonin is in our bones, our joints, our muscles, the peripheral nervous system – lots of places other than our brain,’ he points out. ‘If an antidepressant is designed to increase serotonin, it is going to change things in the body. The chances are that if you’re on them for a while it could cause problems.

‘Look at other examples, such as antibiotics – fine in the short term, but there’s an increasing chance of them being problematic long term.’

Some well-established side effects from antidepressants can come on quite quickly after starting the drugs, and patients are generally warned about them. They include emotional blunting, sleep changes, gastrointestinal problems and weight gain.

Antidepressants known as selective serotonin reuptake inhibitors, or SSRIs – the most common type – can cause sexual dysfunction and a reduced libido.

Other research points to effects on the heart. Older types of antidepressants called serotonin-norepinephrine reuptake inhibitors, or SNRIs, and so-called tricyclic drugs, increase the levels of a key ‘fight or flight’ hormone in the body called noradrenaline, which has been linked to an increased heart rate, a raised blood pressure, higher cholesterol and constricted blood vessels.

Perhaps the most concerning effect on the heart, however, is the suggestion they could prolong the QT interval – a measurement on an electrocardiogram, or ECG, which reflects how long it takes the lower chambers of the heart to contract and reset for each next heartbeat. If the QT interval becomes too long the heart is at risk of a dangerous rhythm disturbance, which can cause palpitations, dizziness and – in rare cases – sudden cardiac death.

A 2025 study presented to a congress of the European Society of Cardiology found using antidepressants for between one and five years increased the risk of sudden cardiac death by 56 per cent. Those taking them the longest had the greatest risk.

Prof Moncrieff says: ‘We already know these drugs can affect the heart’s electrical activity, so it’s plausible they could have these effects, even though other factors may also be influencing the research.’

The clearest link appears to be with type 2 diabetes, according to Prof Moncrieff’s unpublished analysis. Some of the risk may be explained by the weight gain antidepressants can cause, but researchers also believe the drugs may interfere with the body’s blood sugar control.

There is also growing evidence of a higher fracture risk. In 2010, the UK’s Medicines and Healthcare products Regulatory Agency warned doctors that people over 50 taking SSRIs or tricyclic antidepressants could be up to twice as likely to suffer broken bones, with the risk appearing to rise the longer patients stayed on the drugs.

Exactly why remains unclear. People with depression are more likely to smoke, exercise less and have poorer diets – all of which can weaken bones and increase the risk of fractures.

The dementia evidence is far less certain. Depression is itself a major risk factor, making it difficult to separate the effects of the illness from the drugs.

But experts say there is a plausible biological explanation for why older antidepressants, particularly amitriptyline, could affect memory. A 2025 Swedish study also suggested people who already had dementia declined quicker if they were taking high doses of SSRIs.

Prof Moncrieff points out another serious issue with long-term use – that it can make withdrawal symptoms more severe.

These include ‘brain zaps’, low mood, anxiety, flu-like symptoms, agitation and insomnia. Patients should not stop taking their medication suddenly, and should always discuss with a GP how to come off it, which may involve slowly tapering off the dose.

And Prof Moncrieff is clear that these possible long-term effects should make patients question whether antidepressants are still right for them.

‘If these were stunningly effective treatments, maybe it would be worth putting up with the risks,’ she adds. ‘But the majority of the evidence shows they’re not much better than a placebo.’

Dr Alison Cave, MHRA chief safety officer, says each antidepressant had its own ‘unique benefits and potential risks’ and that side effects are clearly outlined in patient information leaflets.

She adds: ‘We recognise the impact that side effects can have on quality of life.

‘It is important patients should continue taking their medicines and not stop or change treatment without first speaking to a healthcare professional. Anyone concerned about side effects, or who experiences symptoms they think may be related to their medicine, should speak to their doctor or pharmacist.’