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Antidepressants can be lifesaving medications for many people with a wide range of mental health issues, including anxiety, depression, obsessive-compulsive disorder, panic disorder, social phobias, and post-traumatic stress disorder. However, taking these psychoactive substances can cause an unpleasant side effect for some: weight gain.
Although many people never gain any extra weight, doctors say concerns about extra pounds are a major reason people hesitate to start taking antidepressants for their mental health. Weight gain is also a reason some people stop taking their medications even if they feel less depressed or anxious while taking them.
A new study now sheds light on the extent of weight gain that can occur – on average – when taking eight of the most commonly prescribed antidepressants.
One of the most widely prescribed antidepressants, sertraline, also known by the brand names Zoloft and Lustral, was associated with an average weight gain of about 0.5 pounds (0.2 kg) at six months. That gain increased to 3.2 pounds (1.46 kg) at 24 months, the study found.
Using this comparison, the researchers found that people taking escitalopram, known by the brand names Lexapro and Cipralex, had an average 15 percent higher risk of regaining at least 5 percent of their baseline weight after six months compared with sertraline. The risk was 14 percent for paroxetine, sold as Paxil, Aropax, Pexeva, Seroxat, Sereupin and Brisdelle, the study said.
Duloxetine, sold under the brand names Cymbalta, Loxentia and Yentreve, was associated with a 10% increased risk of a patient gaining at least 5% of their baseline body weight compared with sertraline, the study found.
A weight gain of 5 percent or more from baseline is considered clinically significant for health, said the study’s lead author, Joshua Petimar, assistant professor of population medicine at the Harvard Pilgrim Health Care Institute and Harvard Medical School in Boston.
The average adult gains an average of 0.5 to 1 kg per year, which over time can contribute to obesity. This weight gain can be due to physical inactivity, stress, lack of sleep and poor dietary choices, such as eating too many ultra-processed foods, as well as taking medications, experts say.
The study, published Monday in the journal Annals of Internal Medicine, used electronic medical record data and body mass to compare weight gain in more than 183,000 people. The researchers looked at weight at 6 months, 12 months and 24 months of people ages 18 to 80 who were starting an antidepressant for the first time.
When analyzing the data in pounds and kilograms of weight gained, people taking escitalopram and paroxetine gained an average of 1.4 pounds (0.63 kilograms) over six months. By 24 months, weight had increased by 3.6 pounds (1.63 kilograms) for escitalopram and by nearly 3 pounds (1.33 kilograms) for paroxetine.
Duloxetine was associated with an average gain of 1.2 pounds (0.55 kilograms) at six months and 1.7 pounds (0.78 kilograms) at 24 months.
“In our study, the average baseline weight was 84 kg, or about 185 pounds,” Petimar said in an email. “This means that in our study, a 5% increase in weight resulted in an average weight gain of 4.2 kg, or about 9 pounds.”
However, the study found no significantly higher or lower risks for citalopram, sold as Celexa, fluoxetine, sold as Prozac, or venlafaxine, sold as Effexor, Effexor XR, Vensir, Vencarm, Venlalix and Venlablue, compared with sertraline.
“We have to remember that these are average values; many people will not gain weight, while others may gain a lot more,” said Dr. Roy Perlis, associate chief of psychiatric research at Massachusetts General Hospital and professor of psychiatry at Harvard Medical School in Boston, who conducted a similar study in 2014. He was not involved in the new research.
Joe Raedle/Getty Images/File
Many common antidepressants can cause weight gain over time, but that’s no reason to avoid taking medication for mental health issues, experts say.
“Still, having average values to work with — and seeing that those averages fit well with previous studies — at least allows us to give people an idea of what to expect,” Perlis said in an email.
Not all patients view weight gain negatively, although patients often prefer to avoid weight gain rather than seek it when taking an antidepressant, Petimar explained. For example, mirtazapine is an antidepressant sometimes used to treat eating disorders.
“We did not look at mirtazapine in our study because it is not considered a common first-line medication for new antidepressant users,” he said.
According to the study, an antidepressant contributed to a small weight loss after six months.
“Bupropion (Wellbutrin and Zyban) on average “Patients taking sertraline had a 15% lower risk of clinically significant weight gain compared with those taking sertraline,” Petimar said.
“Our study did not explore why bupropion was associated with less weight gain than other antidepressants, but other studies have also found that it is associated with less weight gain than other common antidepressants,” he added.
According to the study, when people who took bupropion lost about a quarter of a pound (0.01 kilograms) of weight lost in pounds or kilograms, they gained 1.2 pounds (0.56 kilograms) at 24 months.
Why do antidepressants contribute to weight gain? Science doesn’t yet know, Perlis said.
“It’s surprising that we don’t know the precise mechanism by which antidepressants contribute to weight changes. Worse still, we don’t know much about who is most likely to gain or lose weight, so we can’t make good predictions in advance,” he said.
It’s important to keep in mind, though, that some people lose weight when they’re depressed and lose their appetite. “We find that some people regain the weight they lost as their depression or anxiety improves.”
The best way to manage side effects is to anticipate them, experts say.
“Patients concerned about weight gain should have an open and honest conversation with their doctor about their concerns,” Petimar said.
“There are many clinical factors that determine which medication is best for a given patient,” Petimar said. “These include the patient’s clinical symptoms, their medical history, other medications they are already taking and any side effects they are concerned about.”
Clinicians should consider all of these factors when deciding which treatment is best, he added, while patients can work to avoid weight gain by adopting healthy eating habits and exercising regularly.