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Combination Antidepressant Therapy May Not Improve Odds of Remission Among Chronically Depressed

Science Update

adult male and female comforting each other

A combination of two antidepressants may not be any more effective in treating chronic major depression than a single antidepressant, according to an NIMH-funded study published online ahead of print May 2, 2011, in the American Journal of Psychiatry.


When treating depression, doctors sometimes prescribe a second antidepressant medication if a patient does not improve after several weeks. Because some antidepressants work for some people and not others, the hope is that adding another one will increase the odds of remission. However, treatment guidelines generally do not recommend adding another medication until it is evident the first one is not working.

Madhukar H. Trivedi, M.D., at the University of Texas Southwestern, and colleagues aimed to determine if combination antidepressant therapy as a first treatment step might produce a higher remission rate among people with chronic major depression. In the Combining Medications to Enhance Depression Outcomes (CO-MED) trial, 665 adult participants from several sites around the country were randomly assigned to one of three antidepressant combinations:

  • Escitalopram plus placebo
  • Buproprion sustained release plus escitalopram
  • Venlafaxine plus mirtazapine

Although participants did not know which treatments they were receiving, clinicians were aware of their patients' treatment assignments so that they could adjust doses as necessary to manage symptoms and side effects. The measurement of primary outcome was based on a self-reporting scale called the Quick Inventory of Depressive Symptoms.

Results of the Study

After three months, remission rates among the three groups all were around 38 percent. After seven months, remission rates continued to be similar among the three treatment groups and averaged around 45 percent. However, the venlafaxine plus mirtazapine combination was associated with a higher risk for side effects and serious adverse events compared to the other treatment options.


Despite other research suggesting combination antidepressant treatment may work better than a single medication, neither of the combination therapies in this trial appeared to be more effective than the single medication plus placebo. The researchers suggest that the chronic nature of participants' major depression may be associated with lower remission rates. They also noted that dosage differences may account for the difference in outcomes compared to other studies.

What's Next

Further evaluation is needed to determine if other drug combinations may affect remission rates differently. Results also highlight the need to evaluate biological markers as a means of personalizing treatment and possibly improving remission rates in major depression.


Rush AJ, Trivedi MH, Stewart JW, Nierenberg AA, Fava M, Kurian BT, Warden D, Morris DW, Luther JF, Husain MM, Cook IA, Shelton RC, Lesser IM, Kornstein SG, Wisniewski SR. Combining medications to enhance depression outcomes (CO-MED): Acute and long-term outcomes: a single-blind randomized study. Journal of American Psychiatry. online ahead of print May 2, 2011.