Some antidepressants have more serious physical side effects than others. Here’s how

Anyone who has been prescribed medication to treat depression is familiar with the long list of potential side effects: sleepiness, loss of appetite, headaches, and so on.

But in reality, physical side effects differ significantly from drug to drug, according to a new study that found some antidepressants can cause rapid changes to weight, heart rate, and blood pressure – while others are “relatively benign”.

“Not all antidepressants are built the same when it comes to their physical side effects,” Toby Pillinger, one of the study’s authors and an academic clinical lecturer at King’s College London, said during a briefing with journalists.

The researchers said their analysis, published in The Lancet medical journal, is the first to tie specific physical side effects to individual antidepressant drugs.

The findings could change the way doctors prescribe these medicines, which are taken by up to 17 per cent of adults in Europe and North America, the study said.

“It would be nice to know which antidepressants are better or worse than others for these different physical side effects to guide personalised prescribing,” Pillinger said.

“The problem is that up until now, we haven't had that comparative data available to guide those decisions,” he added.

Pillinger’s team compiled data from 151 studies and 17 reports from the US Food and Drug Administration (FDA). The analysis spanned nearly 59,000 people who took antidepressants or a placebo – a dummy treatment – for a median of eight weeks.

The analysis looked at 30 drugs, including common selective serotonin reuptake inhibitors (SSRIs) such as sertraline, escitalopram, and fluoxetine, as well as other types of antidepressants such as mirtazapine and amitriptyline.

It found “clinically significant differences” in the physical side effects of these drugs, including a four-kilogram difference in weight change between agomelatine and maprotiline and a difference of more than 21 beats per minute in heart rate change between fluvoxamine and nortriptyline.

The researchers estimated that some antidepressants, such as maprotiline and amitriptyline, caused “clinically important” weight gain in nearly half of the people prescribed them.

Overall, they described SSRIs as “relatively benign” compared to other types of antidepressants.

These types of physical side effects can prompt some people to stop taking their prescribed antidepressants, which can worsen their mental health, the researchers said.

“Better tolerability – fewer side effects – means longer duration of treatment for the patient … and the longer the patient takes the medication, the better the outcome they get from the medication,” Dr Andrea Cipriani, a psychiatry professor at the University of Oxford and one of the study’s authors, told journalists.

Independent experts said the findings should be used to develop more personalised treatment options for patients, particularly those with existing cardiometabolic conditions, such as heart disease or diabetes.

“The results underscore the need for routine physical health checks in those treated with antidepressants,” Dr Azeem Majeed, chair of primary care and public health at Imperial College London, said in a statement.

Meanwhile, Prasad Nishtala, a reader in pharmacy and epidemiology at the University of Bath, said the study may underestimate the severity of the side effects.

In a “real-world setting, where patients often receive antidepressants for months or years, the cumulative risks are likely to be higher, particularly among those with chronic depression or existing metabolic comorbidities,” Nishtala said.