Experts say that for up to 25% of people, most antidepressant medications -- including the popular SSRI (selective serotonin reuptake inhibitor) drugs like Lexapro, Paxil, Prozac, and Zoloft -- can cause a weight gain of 10 pounds or more.
"This is a phenomenon that I first noticed years ago when Prozac first came on the market. It didn't initially show up in the clinical trials because most of them were eight to 12 weeks in length, and the weight gain generally occurs with longer use. But it's definitely one of the side effects of this and other antidepressant medications," says Norman Sussman, MD, a psychiatrist and associate dean for postgraduate medical programs at the NYU School of Medicine.
A review published in 2003 in the Cleveland Clinic Journal of Medicine stated that while weight gain is a possible side effect with SSRI antidepressant drugs, it may be more likely to occur after six months or more of use. But SSRIs aren't the only class of antidepressants that may have weight gain as a side effect. Other antidepressant medications, including tricylics (like Elavil and Tofranil) and MAO inhibitors (drugs like Parnate and Nardil), may also cause patients to gain weight with both long-term and short-term use.
"This is clearly a problem for the majority of drugs used to treat depression, and while it doesn't occur with every drug or for every person, when it does happen, it can be a significant problem that we shouldn't just ignore," says Jack E. Fincham, PhD, RPh, professor of pharmacy practice at the School of Pharmacy at the University of Missouri at Kansas City, and author of The Everyday Guide to Managing Your Medicines.
Antidepressants and Weight Gain: What Happens and Why
Although there are a number of theories as to why antidepressants lead to weight gain, Sussman believes that both appetite and metabolism may be affected.
"I have had patients who swear that they are not eating any more, but still gaining weight, so that tells us there is some kind of metabolic influence going on; I have also had patients tell me that they are not only more hungry and eating more, but that the medicines are encouraging a carbohydrate craving that is hard to control, so we know appetite also plays a role," he says.
Fincham says antidepressants may also simply help us to rediscover pleasure in our life -- including food.
"It might be a situation where someone feels so much better when taking an antidepressant that lots of things suddenly start feeling more pleasurable to them, and food is just one of them. So in this instance they may actually be overeating and not even realize they are doing so, says Fincham.
Findings from a group of Italian researchers published in the journal Psychotherapy and Psychosomatics suggest that the simple act of recovery from depression may play a role in the weight gain.
Weight Gain and Antidepressants: Switching Drugs Can Help
While experts may not be certain about why antidepressants cause weight gain, they do know that switching drugs may make a difference.
Some antidepressants may be less likely to affect weight. Effexor and Serzone generally do not cause weight gain, while Wellbutrin can cause weight loss.
Sometimes switching within the same class of drugs can make a huge difference.
