Copyright walesonline
People taking certain antidepressants can put on up to 2kg (4.5lbs) in the first two months of treatment, while patients taking other drugs can expect to shed 2.5kg (5.5lbs), according to a new review. Academics set out to rank antidepressants based on a number of known side effects linked to the drugs in the first eight weeks after starting treatment. The research team, led by academics from the Institute of Psychiatry, Psychology & Neuroscience (IoPPN) at King’s College London, examined data on 58,534 people who took part in more than 150 studies comparing 30 antidepressants with a dummy drug, known as a placebo. They found the most noticeable differences in weight change; heart rate and blood pressure. Researchers said that the findings, which have been published in The Lancet, should “empower” patients but urged them to speak with a medic if they have any concerns. In 2024/25, some 92.6 million antidepressants were prescribed to an estimated 8.89 million patients in England. According to data from NHS Business Services Authority (NHSBSA) the antidepressant sertraline was prescribed to an estimated 2.9 million patients in England last year. This drug, also known as Lustral, was linked to a 0.76kg weight loss and a reduction in heart rate of an average of two beats per minute, but it was also linked to slight increases in systolic and diastolic blood pressure. NHSBSA data show that amitriptyline was given to 2.2 million patients in England in 2024/25. This drug was linked to a 1.6kg increase in weight, on average; an increase in heart rate of nine beats per minute as well as increases in both systolic and diastolic blood pressure. Amitriptyline is a type of drug called a tricyclic antidepressant. This type of antidepressant is not recommended as a first-line treatment for depression as the National Institute for Health and Care Excellence urges medics to try a type of treatment called a selective serotonin reuptake inhibitors (SSRI) – like sertraline – first. As well as being used as a treatment for low mood and depression, amitriptyline can also be prescribed for pain management and migraine. Some 1.4 million people were prescribed citalopram last year, another SSRI. Researchers found this drug was linked to patients losing an average of 0.65kg in weight, and they also, on average, saw decreases to heart rate and systolic blood pressure, but a slight increase in diastolic blood pressure. Overall, researchers found that there was an “approximate 4kg difference in weight change” depending on which drugs patients were prescribed – with those given agomelatine losing an average of 2.44kg while those given maprotiline – which is not usually prescribed in the UK – putting on an average of 1.82kg. On heart rate, they found “over 21 beats-per-minute difference in heart rate change” between fluvoxamine, which reduced heart rate by eight beats per minute, and nortriptyline, which increased it by an average of 13.8 beats per minute. Researchers point out that each 1kg in weight gain increases a patients’ heart risk. And increases in blood pressure can increase a person’s risk of stroke. But they acknowledged that a key limitation of the study was that it focused on the first eight weeks of treatment, and said that further research is needed to assess longer-term side effects. “Antidepressants are among the most widely used medicines in the world,” said senior author of the study Dr Toby Pillinger, an academic clinical lecturer at King’s IoPPN, a consultant psychiatrist. “While many people benefit from them, these drugs are not identical – some can lead to meaningful changes in weight, heart rate, and blood pressure in a relatively short period. Our findings show that SSRIs, which are the most prescribed type of antidepressant, tend to have fewer physical side-effects, which is reassuring. But for others, closer physical health monitoring may be warranted. “The aim isn’t to deter use, but to empower patients and clinicians to make informed choices and to encourage personalised care.” Study author Andrea Cipriani, professor of psychiatry at the University of Oxford, added: “Most clinical decisions – especially in mental health – are still made by physicians with little input from patients. Our results emphasise the importance of shared decision making, the collaborative process through which patients are supported by the clinicians to reach a decision about their treatment, bringing together their preferences, personal circumstances, goals, values and beliefs. “This should be the way forward in the NHS and globally.” Commenting on the study, Rosie Weatherly, information content manager at the mental health charity Mind, said: “It’s so important that people receive mental health support and treatment that considers their individual needs and preferences. As this study highlights, antidepressants vary in their side effects and health professionals need to carefully consider the benefits and risks of different medications for different people. “If you’re already taking medication and you’re worried about its side effects, it’s always OK to ask your doctor or pharmacist for advice. It’s important not to stop taking any medication without advice from a health professional about how to do this safely.” 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, said patients will only be prescribed antidepressants “with good reason” and said GPs would check in with patients two to three weeks after a new prescription to check for side effects. After this patients will be invited for regular medication reviews, she added. "These reviews are particularly important, as this study suggests, given that various factors, including lifestyle, can change how an antidepressant works,” she said.
