Selective serotonin reuptake inhibitors (SSRIs) are the most commonly prescribed antidepressant drugs. One of the most common side-effects associated with all antidepressant drugs is weight gain.
Some SSRIs are associated with a risk of weight gain, especially if the drug is taken long-term. Some studies have found an average increase of about 20 pounds, depending on the medication.
In some cases, however, weight gain can be caused because the medication is improving depression and appetite is normalizing. Other factors, like smoking and lack of exercise, can also contribute to weight gain.