Weight gain is a common side effect of antidepressants, but some types cause people to pack on pounds more than others, a new study says.

Bupropion users are 15% to 20% less likely to gain a significant amount of weight than those taking the most common antidepressant, sertraline, researchers reported July 2 in the Annals of Internal Medicine.

At the same time, escitalopram and paroxetine had a 15% higher risk of gaining  weight compared to sertraline, even though all are selective serotonin reuptake inhibitors (SSRIs), researchers found.

“Our study found that some antidepressants, like bupropion, are associated with less weight gain than others,” said senior researcher Dr. Jason Block, a general internal medicine physician at the Harvard Pilgrim Health Care Institute in Boston.

About 14% of U.S. adults use antidepressants, researchers said in background notes.

For the study, researchers analyzed data for more than 183,000 people ages 18 to 80 who were newly prescribed antidepressants. The team checked the patients’ weight at six months, one year and two years after they started taking one of eight common antidepressants.

Overall, bupropion users gained the least amount of weight compared to users of other antidepressants, researchers said. 

A weight gain of about 5% or more was considered clinically significant.

“Although there are several reasons why patients and their clinicians might choose one antidepressant over another, weight gain is an important side effect that often leads to patients stopping their medication,” Block said in an institute news release. “Patients and their clinicians could consider weight gain as one reason for choosing a medication that best fits their needs.”