"Patients who were normal weight were more likely to transition to overweight, and overweight patients were more likely to transition to obesity if they were treated with antidepressants", the study's co-author Rafael Gafoor, a primary care and public health researcher at King's College London, told Time.
Participants were divided in groups according to their BMI and whether or not they had been prescribed an antidepressant in a given year.
"Currently, we are still unable to identify patients at higher risk of weight gain with antidepressants".
In praising Gafoor's group for their study, the editorialists agreed with the recommendation that providers provide lifestyle and weight management advice to patients on these agents and to utilize these findings when selecting patients' antidepressant prescriptions.
The researchers said that the results suggest the widespread use of antidepressants "may be contributing to long-term increased weight gain at a population level, and that the potential for weight gain should be considered when antidepressant treatment is indicated". Other antidepressants that were tied to the highest associated risks for weight gain compared to other antidepressants included duloxetine (1.23, 95% CI 1.15-1.31), escitalopram (1.23, 95% CI 1.17-1.29), and citalopram (1.26, 95% CI 1.23-1.28).
The risk of weight gain should not necessarily discourage people from taking antidepressants, Gafoor says, but patients should discuss the risk of weight gain with their doctors when beginning a new treatment plan, and potentially develop long-term strategies for keeping it in check.
"Our study adds to previous data by providing longer follow-up (up to 10 years) of antidepressant treatment, showing that the risk of weight gain is increased for at least the first five years of treatment", write the King's College team. Their body mass index (BMI) had been recorded at least three times by a doctor between 2004 and 2014. They monitored them over the next 10 years, while accounting for other factors like age, diseases, and whether they smoked or took drugs, which could all affect weight gain.
"For every 59 people taking antidepressants, one extra person would gain at least 5 percent weight over the study period", they said.
Factors like age, sex, and whether participants had health problems like diabetes or cancer didn't have much of an impact on the results.
The study comes with many caveats.
The study doesn't prove that the drugs caused weight gain, according to its lead author, only that there's a link that may help explain the rise in obesity.
Depression in itself can also cause weight gain because people sometimes aren't as motivated to exercise or eat well. It's better to be aware of the risks than to stop taking your medication as a result of undesirable side effects.