The side effects of antidepressants have been ranked for the first time, revealing stark differences between the different medications.
Some antidepressants caused patients to gain up to 2kg of weight or increase their heart rate by as much as 21 beats every minute.
About eight million people in the UK take antidepressants, which have long been known to cause side effects. However, the study, conducted by King's College London and the University of Oxford, is the first to produce a ranking system so the effects can be easily compared.
The team analysed 151 studies of 30 drugs commonly prescribed for depression, involving over 58,500 patients. The results were published in the Lancet medical journal.
What did the study find?
Not everybody experiences side effects from antidepressants, however, the study showed:
- An eight-week prescription of agomelatine was linked to a 2.4kg drop in weight, while maprotiline led to almost 2kg of weight gain.
- There was a difference of 21 beats per minute between fluvoxamine, which slowed the heart, and nortriptyline, which accelerated it.
- There was an 11 mmHg difference in blood pressure between nortriptyline and doxepin
The research found that SSRIs such as paroxetine, citalopram, escitalopram and sertraline, which are most commonly prescribed, tended to have fewer side effects.
Fluoxetine, an SSRI that is also known as Prozac, was associated with weight loss and higher blood pressure.
However, medical experts have flagged that there are still “knowledge gaps” in the study.
“Despite the improved understanding of antidepressants and their effects, there are still knowledge gaps. Other common side effects such as sexual dysfunction and gastro-intestinal issues are not described in the study,” Colin Davidson, Professor of Neuropharmacology at the University of Lancashire, told The Standard.
“Many studies report only a narrow set of side effects, neglecting metabolic factors and gender-based differences. The study emphasises the need for future trials to more comprehensively measure side effects and include gender in their analyses.”
What does the study mean for people on antidepressants?
The researchers who conducted the study said that they did not want people to stop their treatment, rather called for the medications to be better tailored to the needs of individuals.
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."
So what should patients taking antidepressants do if their medication ranks highly for side effects?
“The first thing I’d say to patients taking antidepressants is that it is important not to immediately stop taking your medication. An abrupt stop can cause severe withdrawal effects with some antidepressants,” Professor Davidson told The Standard.
“If you are thinking about switching your medication, you should consult your doctor first so they can suggest an alternative antidepressant, as well as a schedule to taper off your current medication to avoid severe withdrawal symptoms. I’d also recommend speaking with your pharmacist who may be able to offer additional guidance.”
What’s next?
The researchers are currently developing a free online tool that will support doctors and patients in selecting the best drug for them. However, it’s likely that changes in prescribing will be gradual.
Dr Suzanne Wylie, GP and medical adviser for IQdoctor told The Standard that while the study is “unlikely to prompt a blanket shift in prescribing habits,” it serves “as a reminder to consider individual patient factor, such as age, comorbidities, and previous medication responses, when selecting an antidepressant.”
