SIDE effects of different antidepressants have been ranked for the first time, revealing huge differences between drugs.

Academics looked at the impact medications had on patients in the first eight weeks after starting treatment, with some causing patients to gain up to 2kg in weight or vary heart rate by as much as 21 beats every minute, the BBC reported on Wednesday.

Researchers warned the gulf in side effects could affect people’s health and whether they could stick to their prescription. They said nobody reading this should stop their treatment, but have called for antidepressants to be closely matched to the needs of each person.

“There are big differences between [antidepressants] and this is important not just for individual patients, but large numbers of people are taking them, so even modest changes could have a big effect across the whole population,” said researcher Prof Oliver Howes.

We’ve always known antidepressants affect physical health. The study by King’s College London and the University of Oxford is the first to produce a ranking so that the effects of medicines can be easily compared.

The team analysed 151 studies of 30 drugs commonly used in depression, involving more than 58,500 patients.

Not everybody develops side effects, but on average, the results published in the Lancet Medical Journal showed an eight-week prescription of agomelatine was linked to a 2.4kg drop in weight compared with maprotiline, which led to nearly 2kg of weight gain.

A difference of 21 beats per minute between fluvoxamine, which slowed the heart, and nortriptyline, which sped it up. An 11 mmHg difference in blood pressure between nortriptyline and doxepin

“Clearly no two antidepressants are built the same,” said Dr Atheeshaan Arumuham, from King’s College London. Those differences can stack up in ways that become clinically important, including an increased risk of heart attack or stroke. It means even people with the same diagnosis could be better suited to different antidepressants depending on their own preferences and other health conditions.

Dr Toby Pillinger told BBC Radio 4’s Today programme: “The majority of the studies we looked at were relatively short. We’re looking at eight weeks’ duration, and still within that duration, we were seeing large changes in physical health parameters, which we would argue have clinical relevance. “The last thing I want is for this story to be scaring people,” he added.

“I want to see this as empowering individuals to take the initiative and to engage in shared decision-making with their practitioner.

Which antidepressant is best for me?

In a hypothetical scenario, Sarah, 32, John, 44, and Jane, 56, have all received the same depression diagnosis and have been recommended antidepressants.

For Sarah, the priority is avoiding weight gain, while John already has high blood pressure, and Jane has raised cholesterol.

Dr Pillinger, who worked through the examples for the BBC, says each would be recommended a different medicine. Sarah should have an antidepressant that avoids weight gain, such as agomelatine, sertraline or venlafaxine, rather than amitriptyline or mirtazapine, which are more likely to increase weight.

Published in Dawn, October 23rd, 2025