Antidepressants differ in side-effects such as weight gain, UK research finds

People taking certain types of antidepressants can gain up to 2kg (4.5lbs) in weight within the first two months of treatment, while patients taking other drugs can lose the equivalent or more, according to a major review of potential side-effects.

The research, led by academics at King’s College London and the University of Oxford, found that while some antidepressants can cause notable changes in body weight, heart rate and blood pressure, others do not cause such physical changes.

Researchers are calling for antidepressant treatment guidelines to be updated to reflect these findings.

Antidepressants are medications that can help with mental health conditions such as depression and anxiety, and are recommended for up to two years of use in most cases.

The study involved analysis of data from 151 clinical studies on antidepressants, comparing the physical health effects of 30 different antidepressants in more than 58,000 people.

The researchers found there to be notable variation in side-effects between different medications, despite most of the studies analysed involving only eight weeks of antidepressant use.

For example, there was a difference of up to 4kg in average weight change between some drugs: equivalent to about 2.5kg of weight loss on agomelatine, compared with about 2kg of weight gain with maprotiline. Weight gain occurred in nearly half of people prescribed drugs such as maprotiline or amitriptyline, whereas more than half of those taking agomelatine experienced weight loss.

The study also found a 21-beat-a-minute difference in heart rate between people taking fluvoxamine and nortriptyline. An 11 mmHg difference in blood pressure was found between nortriptyline and doxepin.

Dr Toby Pillinger, a clinical lecturer at KCL, said: “Antidepressants are among the most widely used medicines in the world. 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 [selective serotonin reuptake inhibitors], 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.”

Andrea Cipriani, a professor of psychiatry at the University of Oxford, said: “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.”