Many of my patients ask me why they are on more than one medication for the treatment of anxiety or depression. The answer lies in understanding the vast complexity of the human brain. The brain is composed of over 100 billion neurons. The next most complex organ in our body — the heart – is composed of 100 million – and so the brain is on a totally different order of magnitude. Modern neuroscience has continued to make major advances in understanding that complexity, but it still remains a vast and not yet fully understood system. What we do know is that compared with 1989 when Prozac was first released in the United States, we had one identified receptor for serotonin. Now there are more than 30 serotonin receptors that have been identified and multiple subunits where antidepressants bind.
For this reason — it is hard to come up with one medication that will effectively address all of the receptors. About 10-15% of patients who begin a treatment are fortunate and only require one medication at a time. But often, to cover all of the necessary pathways in which neurobiology goes haywire in depression and anxiety — it requires a few — not unlike a painter working on a canvas and trying to achieve subtle effects with a variety of colors. The other good thing about combined medications — is that they reduce side effects. For example, many antidepressants in the SSRI (selective serotonin reuptake inhibitor family) cause decreased sexual function. Wellbutrin — a dopaminergic stimulator — is an excellent way of increasing libido and improving quality of life. And creating an excellent life, not merely a tolerable one, is what good mental health treatment should be about.