New research challenges the idea that there is a link between depression and an imbalance in the levels of serotonin in the brain.
It once again questions the use of commonly used antidepressants, which work on the basis that depression is related to lower levels of serotonin in the brain.
Taking SSRIs — like Prozac, Paxil and Zoloft — increases the levels of serotonin in the brain and, supposedly, helps lift depression.
However, there is no way to measure serotonin in the brain and it’s not known exactly how SSRIs actually work.
Researchers now know that around two-thirds of people continue to be depressed even while taking the drug.
Critics of SSRIs say that 80% of their effect is placebo: in other words, the belief or hope that a medicine might work is enough to make you feel a bit better.
One study has even found them clinically insignificant.
This vital debate has now inspired researchers to genetically engineer mice that are incapable of producing serotonin in their brains (Angoa-Pérez et al., 2014).
In theory, they should have bred a race of super-depressed mice.
It turns out, though, that the reality was quite different.
Professor Donald Kuhn and colleagues, who bred the mice, ran a series of behavioural tests to determine the effects of lowered serotonin levels.
They found the mice showed no signs of depression but were extremely aggressive and demonstrated compulsive behaviour.
The most surprising finding, though, was that when under stress, they behaved in exactly the same way as normal mice.
The study questions the well-established chemical explanation for how depression affects the brain, and how it should be treated.
Although this is only a study of mice, it is another blow for a range of drugs that is currently the most common form of treatment for depression.
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Image credit: cora alvarez