Most medications prescribed for depression can cause weight gain, according to the Mayo Clinic. Antidepressants that are more likely to cause weight gain than others include tricyclic antidepressants, paroxetine, mirtazapine, trazodone and monoamine oxidase inhibitors, or MAOIs. However, individuals vary in their responses to medications, so some patients may not experience this side effect. In addition, weight gain may be a result of inactivity or increased appetite rather than the medication. Since weight gain is the side effect most likely to cause patients to terminate treatment for depression, prescribing an antidepressant that does not affect body weight can help to improve compliance.
Venlafaxine is a serotonin and norepinephrine reuptake inhibitor, or SNRI, according to the Mayo Clinic. Venlafaxine affects the chemicals in the brain that, when imbalanced, cause depression. Side effects include high blood pressure and sexual dysfunction. The medication does not cause weight gain in the short-term, reports Dr. Rashmi Deshmukh in the July 2003 issue of the "Cleveland Clinic Journal of Medicine." However, there are insufficient data on the long-term effects on weight.
Atypical antidepressants cause fewer sexual side effects than other medications prescribed for depression, according to the Mayo Clinic. Bupropion, an atypical antidepressant, may suppress appetite and cause weight loss, so it is not appropriate for patients with eating disorders. It is also not prescribed for patients with seizure disorders. It is, however, effective in helping patients quit smoking.
Selective Serotonin Reuptake Inhibitors
Selective serotonin reuptake inhibitors--SSRIs--are the most commonly prescribed medications for major depressive disorder, according to the Merck Manual. These medications, including fluoxetine, sertraline, citalopram and escitalopram, are safe and effective in relieving depression and tend not to cause weight gain, according to the Mayo Clinic. Paroxetine is the only SSRI that may cause an increase in weight. Side effects of SSRIs may include sexual dysfunction, nausea, diarrhea, headaches and agitation, but in most cases these effects are mild and manageable. Suicidal tendencies may occur, especially in children and adolescents, according to the Merck Manual.
Nefazodone is an antidepressant that helps to balance the chemicals in the brain to elevate the patient's mood. Nefaxodone has less likelihood of causing weight gain than other antidpressants in both short-term or long-term use, according to Dr. Deshmukh. Most patients have no side effects from nefazodone. If side effects occur, they may include decreased sex drive, fever, frequent urination, memory loss, confusion, digestive symptoms, ringing in the ears, abnormal skin sensations, abnormal dreams and sleeplessness, according to Drugs.com.