Between 50% and 75% of people show some improvement on first taking an antidepressant but only about a third completely recover after taking just one drug. Previous research has shown that a combination of drugs can have a better effect and a team of researchers led by Pierre Blier of the University of Ottawa studied the effectiveness of adding mirtazapine to various different antidepressants. Mirtazapine belongs to a different class of drugs to most other antidepressants and is classified as a noradrenergic and specific serotonergic antidepressant (NaSSA). 105 people with major depression received either fluoxetine on its own, or mirtazapine combined with fluoxetine, venlafaxine or bupropion. The recovery rates were 25% for fluoxetine, 52% for mirtazapine and fluoxetine, 58% for mirtazapine and venlafaxine and 46% for mirtazapine and bupropion. There were no extra side effects from using a combination of different drugs.
Blier, Pierre ... [et al] - Combination of antidepressant medications from treatment initiation for major depressive disorder: a double-blind randomized study American Journal of Psychiatry March 2010, 167(3), 281-288