Depression: Overestimated Influence of Serotonin?
All content is checked by medical journalists.MunichPeople with depression lack the happiness hormone serotonin - this thesis has long been considered the most likely explanation for the mental illness. But now doubts arise about the hypothesis.
The connection seemed at least plausible - the messenger substance serotonin lifts the mood and promotes the drive. Both positive impulses plummet in people with depression. The reason - lack of serotonin in the brain - or so it was believed.
Accordingly, a large part of modern drug treatments aims to remedy such a deficiency. So-called serotonin reuptake inhibitors (SSRIs) delay the breakdown of the happiness hormone - the level rises.
Serotonin hypothesis with blemishes
However, the hypothesis has a few flaws: It remains inexplicable why the drugs take weeks to develop their effects, even though the biochemical mechanism takes effect quickly. Above all, however, the psychopills do not work sufficiently in 60 to 70 percent of patients.
US researchers have therefore set out to test the serotonin hypothesis. To do this, a team led by Donald Kuhn from Wayne State University genetically programmed mice so that they were no longer able to produce serotonin.
Depression test for mice
Actually, the rodents should have developed behaviors that correspond to those of people with depression, for example hopelessness and lack of drive. This was tested at the mouse level: Depressed mice are less interested in sweets than usual. If you put depressed animals in a narrow cylinder of water, for example, they stop paddling faster than healthy mice.
But that was not the case with the genetically modified mice in the study - they reacted in such tests and under stress just like their non-genetically manipulated conspecifics. And they responded similarly to antidepressants too. The only difference: the serotonin-free mice behaved compulsively and extremely aggressively.
Rethinking drug research
The results of the study indicate that serotonin does not play the key role in the development of depression, as assumed. The researchers speculate that this could steer the direction of antidepressant research in a completely new direction.
Along with anxiety disorder, depression is the most common mental disorder. An estimated four million people currently suffer from it in Germany. (cf)
Source: Mariana Angoa-Pérez et al .: Mice Genetically Depleted of Brain Serotonin Do Not Display a Depression-like Behavioral Phenotype. ACS Chem. Neurosci., Article ASAP, DOI: 10.1021 / cn500096g, Publication Date (Web): August 4, 2014
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