Common scientific beliefs about serotonin levels in depression and how antidepressants act on the brain appear to be completely backwards, according to a paper from Canadian and American researchers in Neuroscience & Biobehavioral Reviews.
The authors noted that it is impossible to measure serotonin levels directly in a human brain, but the dominant theory for fifty years has been that depressed people have lower serotonin levels, while SSRI antidepressants keep serotonin levels high by blocking its re-absorption.
However, in their review of the scientific literature they could find no evidence to support this theory, while there was compelling evidence to support an opposing theory: that serotonin levels increase substantially during depressive episodes.
“The best available evidence appears to show that there is more serotonin being released and used during depressive episodes, not less,” stated a press release about the study. This apparently indicated a greater allocation of the neurotransmitter to conscious thought over other body functions.
When SSRIs are added and serotonin levels increase even more, it is actually the brain’s own compensatory response to reduce the escalating serotonin levels that improves symptoms in some people. And because the brain’s response takes time, that is the reason, they argued, that SSRIs are typically said to take several weeks before they have any positive impact.
Over the long term, though, the brain’s regulating systems are destabilized by the drugs. In the press release, the lead author stated, “It’s time we rethink what we are doing. We are taking people who are suffering from the most common forms of depression, and instead of helping them, it appears we are putting an obstacle in their path to recovery.”
Science behind commonly used anti-depressants appears to be backwards, researchers say (McMaster University press release on ScienceDaily, February 17, 2015)
Andrews, Paul W., Aadil Bharwani, Kyuwon R. Lee, Molly Fox, and J. Anderson Thomson Jr. “Is Serotonin an Upper or a Downer? The Evolution of the Serotonergic System and Its Role in Depression and the Antidepressant Response.” Neuroscience & Biobehavioral Reviews 51 (April 2015): 164–88. doi:10.1016/j.neubiorev.2015.01.018. (Abstract)