A recent study comparing weight gain with use of eight different first-line antidepressant drugs suggests that those using bupropion were 15–20% less likely to experience significant weight gain than those using sertraline (the most commonly prescribed antidepressant drug).

Antidepressants are among the most commonly prescribed medications in the United States, with 14% of adults using them.

However, weight gain is a frequent side effect that can affect long-term health and may force some patients to discontinue their treatment, resulting in ill health.

Although antidepressant medications generally cause weight gain, the extent can vary between different drugs.

Researchers at the Harvard Pilgrim Health Care Institute conducted a study to find out which common antidepressant medications were associated with the most and the least weight gain.

“Patients and their physicians often have several options when starting an antidepressant medication for the first time. This study provides important anecdotal evidence about the amount of weight gain to be expected after starting some of the most common antidepressant medications,” said lead author Joshua Pettimer, MD, assistant professor of population medicine at Harvard Pilgrim Health Care Institute.

The study, published in the Annals of Internal Medicine, used electronic health records from eight US health systems, including data on 1,83,118 adults aged 18-80 years who were new users of antidepressant drugs.

Although randomized control trials are the gold standard for comparing drug effects, they are expensive and time-consuming. Instead, researchers simulate a randomized trial by designing an ideal trial and matching the data as closely as possible.

The researchers compared changes in weight 6, 12 and 24 months after starting eight common antidepressant medications – sertraline, citalopram, escitalopram, fluoxetine, paroxetine, bupropion, duloxetine and venlafaxine.

Results showed that bupropion users gained the least weight compared to users of other antidepressant medications. Bupropion users were about 15-20% less likely to gain a clinically significant amount of weight compared to those taking sertraline.

Clinically significant weight gain was defined as an increase in body weight of 5% or more.

The study also found that many patients were taking medicines that caused more weight gain than other medicines available in the same category.

For example, among the selective serotonin reuptake inhibitors (SSRIs), escitalopram and paroxetine were associated with a higher risk of significant weight gain in the first six months than sertraline.

“Although there are many reasons patients and their physicians may choose one antidepressant medication over another, weight gain is a significant side effect that often causes patients to stop taking their medication,” said senior author Jason Block, MD, a general internal medicine physician and associate professor of population medicine at Harvard Pilgrim Health Care Institute.