Acetaminophen (a.k.a paracetamol) relieves some types of headache. But this does not mean that these headaches are caused by acetaminophen deficiency. The brain doesn’t even produce acetaminophen.
The point of this analogy is to make clear that a medicine can work even if it is not acting on the cause of the symptom. In many cases a medicine can work even when the cause of the symptom is completely unknown.
This is the case with SSRIs — they alleviate some forms of depression, and also fail to work for many depressed people, but we still don’t know why. Lots of active research is going into this.
Quite a bit of research suggests that serotonin affects plasticity, so it seems as if the effectiveness of SSRIs arise through changes to neuronal circuits, rather than through changing the levels of serotonin as such. This would explain why the beneficial effects of SSRIs typically take weeks to show up, even though the levels of serotonin rise on the order of hours after taking a tablet. Changes to neuronal circuits involved in emotion and motivation may take quite a while to become effective.
Anyway, SSRIs remain controversial, and not just because they often fail to work. Even in people for whom it does work, the effects may not be long-lasting, and can often come with adverse side-effects. Much more research will be needed before we can say we understand what is going on with these medications, and with the disorders they are aimed at treating.
Further reading
- Yohan John’s answer to Does depression cause the drop in serotonin levels or does lowered serotonin levels cause depression?
- Yohan John’s answer to What are the symptoms of low serotonin and imbalance of dopamine?
- Serotonin deficiency as cause of depression – is it a myth?
- Is the Link Between Depression and Serotonin a Myth?
- The Media and the Chemical Imbalance Theory of Depression
- What are the real risks of antidepressants? – Harvard Health
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This originally appeared on November 14, 2018 as an answer to the following question on Quora:
Both St John’s Wort, an SSRI, which I tried once, and Prozac, with which I persisted for the three weeks of my initial prescription, made me feel utterly wretched, and disconnected from my own very existence. I cannot imagine how any degree of depression could have made me feel worse. Since then, I have avoided all mood-altering medication.
I was slightly surprised not to see this sort of thing mentioned in your source’s list of side effects. Unless my reaction is highly unusual, I think it should be.
Yes I think there needs to be much more awareness of the side-effects.
Did you see this New Yorker article?
https://www.newyorker.com/magazine/2019/04/08/the-challenge-of-going-off-psychiatric-drugs
When I described my symptoms to the physician who had prescribed the Prozac, he was clearly shaken. Fortunately, I experienced no side-effects from withdrawal.
Thanks for the link to the New Yorker article.The complexities described there may well prevent people who experience side-effects from talking about them, and a very reasonable wish to avoid making self-fulfilling suggestions may prevent physicians from warning their patients.
True. Almost a Catch-22 situation!
As far as I know, SSRIs don`t work at all for more than 1/3 of patients.
Even the theory of increased plasticity cannot explain this phenomena.
In line with critics, therapists often highlight that you have to “believe in” the effect of SSRIs.
…which means if there is no effect, it is the responsibility / negative attitude of the patient.
Wow. Blaming the patient seems a bit extreme! It is unheard of in the basic research literature. And I think that’s a good thing.
In fact, nero-science and the know how of the brain is very limited. If you look at the history of SSRIs, you will discover that there is no evidence of anti depressant effects or root-cause relations between depression and serotonin levels.
SSRIs also work with a placebo effect.
Well I am a neuroscientist and I can assure you that that is not quite right. There are people who do experience an anti-depressant effect over-and-above placebo. All drugs that are approved for use have to exceed the placebo effect. That is distinct from the observation that serotonin levels are not causal when it comes to depression. Paracetamol can still help with pain relief even though pain is not caused by lack of paracetamol.
right but according to my research it was an incident that an anti depressant effect was discovered …and it shall be still unclear if serotonin increase is effective.
Didn’t you read this post? That is exactly what this is about. Also see this Quora answer I wrote about it. https://www.quora.com/Whats-the-current-status-of-the-serotonin-imbalance-theory-of-depression/answer/Yohan-John
The effectiveness of a drug has nothing to do with whether it was discovered accidentally, or even whether we know how it works. This is a very important thing to understand.
I disagree. If you experience the bundle of very negative side effects, you want to know how it works and if there are long term undesirable damages.
Besides it is important to understand anti- depressants better if they are not of help for a huge group of patients. Of course, you have to investigate the reason for failure to be able to exclude options on your search for something new.
Another challenge might be the fact that the cause for depression is not clear.
The theory of a chemical imbalance is not proven 100% but used as a frequent marketing slogan.
Thank you for the link.