A major UK study has found significant differences in the side-effects of antidepressants, including weight change, heart rate, and blood pressure.
Researchers from King’s College London and the University of Oxford analysed data from 151 clinical trials involving more than 58,000 people taking 30 different antidepressants. They discovered that some drugs can cause up to 2kg of weight gain within two months, while others may lead to comparable weight loss.
For example, maprotiline and amitriptyline were linked to weight gain in nearly half of patients, while over half of those taking agomelatine experienced weight loss. The study also found a 21 beats-per-minute difference in heart rate between fluvoxamine and nortriptyline, and an 11 mmHg blood pressure difference between nortriptyline and doxepin.
Lead author Dr Toby Pillinger said the findings highlight that antidepressants “are not identical” and can have meaningful physical effects even within weeks. He noted that SSRIs—the most prescribed class—tend to have fewer side-effects, but some other drugs may require closer monitoring.
Co-author Prof Andrea Cipriani added that the research reinforces the need for shared decision-making between patients and clinicians, ensuring treatment choices reflect individual preferences and health needs.
The researchers have called for updated clinical guidelines to reflect these variations and support more personalised antidepressant care.
