Antidepressant combination therapy—prescribing two or more antidepressant drugs together—is a common practice. But combination therapy may not necessarily be helpful, and in fact it might increase one’s chances of experiencing drug side effects, according to a study to be published in the American Journal of Psychiatry and reported in a University of Texas (UT) Southwestern Medical press release.

Scientists in the Combining Medication to Enhance Depression Outcomes (CO-MED) study followed 665 patients, ages 18 to 75, with major depressive disorder for almost one year. Scientists divided patients into three groups and put each on a different drug regimen.

Researchers gave the first group escitalopram (Lexapro) and a placebo. The second group received both escitalopram and bupropion (Wellbutrin). The third group took two different antidepressants: venlafaxine (Effexor) and mirtazapine (Remeron).

Scientists found that after 12 weeks of treatment, the three groups had almost identical response rates (52 percent) and remission rates (38 to 39 percent). In addition, response and remission rates for each group remained much the same after seven months of treatment. But members of the third group, who took both venlafaxine and mirtazapine, experienced more side effects than the other two.

“The clinical implications are very clear,” said the study’s lead author, Madhukar H. Trivedi, MD, chief of the division of mood disorders at UT Southwestern Medical Center. “The extra cost and burden of two medications is not worthwhile as a first treatment step.”

But other studies have shown benefits from antidepressant combination therapy, so don’t rush to change a combo regimen that’s working for you. If your combination therapy is leading to side effects or breaking your budget, though, it may be time to discuss alternatives with your doctor.

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