Dr Kasim Ahmed said in the UK 8 million take antidepressants as new research found that some drugs can have serious side effects
07:00, 24 Oct 2025Updated 08:54, 24 Oct 2025
Dr Kasim Ahmed told BBC Morning Live viewers some antidepressants had been shown to have worrying side effects(Image: BBC)
A BBC expert has raised concerns about a number of commonly prescribed antidepressants currently used by eight million Britons. Fresh research published this week has revealed that individuals taking certain antidepressants may gain up to 2kg (4.5lbs) within the initial two months of treatment, whilst those on alternative medications could lose 2.5kg (5.5lbs).
Researchers aimed to categorise antidepressants according to various recognised side effects associated with the medications during the first eight weeks of treatment. The study team, headed by experts from the Institute of Psychiatry, Psychology & Neuroscience (IoPPN) at King’s College London, analysed information from 58,534 participants across more than 150 trials comparing 30 antidepressants against a placebo.
Appearing on BBC Morning Live today, Dr Kasim Ahmed described the headlines as ‘pretty scary’ “if you’re one of the 8 million people in the country that uses an antidepressant.”
He continued: “The important thing that needs to be mentioned here… is that these medications have been given for a reason and that reason is because of a mood disorder of some kind, whether that’s depression, anxiety, bipolar affective disorder. These are very, very good medications at solving someone’s problems or helping someone deal with some of the problems that they’re facing as a result of these mood-based disorders.”
The researchers discovered the most significant changes occurred in weight fluctuation, heart rate and blood pressure levels. Dr Kasim revealed that the study examined data from 50,000 patients and assessed the medication’s effects between 8 – 12 weeks after commencing treatment.
He said: “What we’re going to focus on now is the three bigger findings of it, which was weight gain, changes to your blood pressure and changes to the heart rate.”
Content cannot be displayed without consent
“Essentially what it found is that there’s lots of different medications of different classes that can cause changes in your weight as this all starting. If we look at weight gain specifically first, some antidepressants, specifically things like amitriptyline, if you’re on that is something that we use relatively commonly here, can cause an increase in weight of up to 2 kilogrammes within the 1st 12 weeks of you starting that medication.
“But, however, other antidepressants can cause a big loss in weight as well, so things like sertraline or citalopram can cause a loss in weight up to 1 kilogramme themselves once you’ve started the medication. But this is a side effect that affects some people, not everyone who’s on those medications.”
Fresh warning issued to anyone taking sertraline, amitriptyline, citalopram or maprotiline Dr Kasim warned the effects on heart rate could trigger ‘problems’. He explained: “So if you’re taking amitriptyline or nortriptyline is a big one, it can cause an increase in your heart rate over the course of 8 to 12 weeks of starting the medication, and sertraline, fluoxetine, so these are the medications which are of a different class, can cause a lowering of your heart rate.”
Regarding blood pressure, he added: “So same classes of drugs, amitriptyline, nortriptyline can cause an increase in your blood pressure, not a massive increase by about 10 points over, an average period of time, and similarly. Sertraline fluoxetine citalopram, which are a class within themselves, can cause a dropping of your blood pressure.”
During 2024/25, approximately 92.6 million antidepressants were dispensed to around 8.89 million patients across England. NHS Business Services Authority (NHSBSA) figures reveal the antidepressant sertraline was dispensed to roughly 2.9 million patients in England during the past year.
The medication, which goes by the brand name Lustral, was associated with a 0.76kg weight reduction and a decrease in heart rate averaging two beats per minute, though it was also connected to minor rises in systolic and diastolic blood pressure. NHSBSA statistics indicate that amitriptyline was dispensed to 2.2 million patients in England during 2024/25.
This medication was associated with a 1.6kg weight gain on average, alongside a heart rate rise of nine beats per minute and elevated systolic and diastolic blood pressure readings.
Amitriptyline belongs to a class of drugs known as tricyclic antidepressants. This category of antidepressant isn’t recommended as an initial depression treatment, as the National Institute for Health and Care Excellence advises doctors to first try selective serotonin reuptake inhibitors (SSRIs) – such as sertraline.
Professor Azeem Majeed, chairman of primary care and public health at Imperial College London, said: “For patients and clinicians, the results underscore the need for routine physical health checks in those treated with antidepressants.
“Moreover, awareness of these side effects is essential to support shared decision-making about the risks and benefits of treatment with antidepressants.”
Dr Lade Smith, president of the Royal College of Psychiatrists, said: “Antidepressants play a key role in the treatment of more severe depression and are particularly effective when used in combination with talking therapies. As with all drugs, antidepressants have side effects, and we very much welcome this study which helps improve our understanding of some of the physical side effects that can be caused by different types of antidepressants.
“These findings will help patients and clinicians choose the medication that is best suited to their personal needs.”
Professor Kamila Hawthorne, chair of the Royal College of GPs, assured that patients will only be prescribed antidepressants “with good reason”. She added that GPs would follow up with patients two to three weeks after a new prescription to monitor for side effects.
She further stated that patients will be invited for regular medication reviews. “These reviews are particularly important, as this study suggests, given that various factors, including lifestyle, can change how an antidepressant works,” she said.