Depression: a study on the causes of the disease provokes controversy – 08/11/2022 at 09:30

In their work, psychiatrists Joanna Moncrieff and Mark Horowitz question the use of antidepressants to treat depression, which is not linked to a chemical imbalance.


(AFP / DAMIEN MEYER)

The interest of

antidepressants would be called into question

because depression is not related to a chemical imbalance. The thesis, recently defended by a British psychiatrist, is widely disputed but this controversy has the advantage of illustrating the difficulties in understanding this disease.

“Our study (…) calls into question the basic idea behind the use of antidepressants”, affirmed the end of July the psychiatrists Joanna Moncrieff and Mark Horowitz on the site The Conversation, relaying a work published in the journal Molecular Psychiatry . This study tackles the serotonin hypothesis. This suggests that depression is linked to a deficiency of this molecule involved in the transmission of emotions in the brain.

The work, based on a compilation of previous publications and therefore a priori more solid than an isolated study, concludes that

no link has been proven between a deficit of serotonin and the presence of depression in an individual

. For its authors, it is a profound questioning of a hypothesis that has served for decades as a framework for numerous studies. The majority of current antidepressants have indeed been developed to act on serotonin levels.

A challenged study

But many critics quickly targeted this study and, even more, the presentation made by Joanna Moncrieff, a psychiatrist known for

his skepticism towards biological explanations of depression

, as well as his radical speech against the pharmaceutical industry. “Overall, I agree with the conclusions of the authors but I would not have such inflexible certainties”, commented the British psychiatrist Phil Cowen, in a reaction to the Science Media Center.

The criticisms of Phil Cowen and other colleagues are of different orders. Some question the methodology of the study, in particular the fact of not measuring serotonin directly but an indirect trace of it;

others accept his conclusions but reject their novelty

. “No mental health specialist would currently support the idea that a pathology as complex as depression is explained by the deficit of a single neurotransmitter”, notes Phil Cowen.

The argument does not hold for Joanna Moncrieff, according to whom the serotonin hypothesis, even in a reduced version, still holds an important place in the discourse of psychiatrists. “And especially,

even if eminent psychiatrists are beginning to doubt the links between depression and deficit

of serotonin, no one has warned the general public”, ironically on her blog the author, who appears to break with “dominant psychiatry”.

An argument against current antidepressants

The links between depression and serotonin are, in fact, well anchored in popular imagery. In 2019, the French author Michel Houellebecq had thus titled “Sérotonine” a novel whose main character is depressive. But it is not the calling into question of the serotonin hypothesis that arouses the strongest criticism. This is

the fact that Joanna Moncrieff makes an argument against current antidepressants

exceeding the conclusions of his own study.

This “is a serious work, which is part of the continuation of other work and which counts in the discussion between experts concerning the mechanisms of depression”, admits to AFP the Swiss psychiatrist Michel Hofmann. ”

But I don’t think this is an article that should have a short-term impact on the prescription of antidepressants.

“, he warns. Because for Johanna Moncrieff – who certainly warned that an antidepressant should not be abruptly interrupted at any price -, one must necessarily doubt the benefits of treatments developed on the basis of a questioned hypothesis.

“We are left with hypotheses

However, many psychiatrists, including Johanna Hofmann, emphasize that the effectiveness of these treatments, whatever the root cause, has been scientifically assessed. ”

The mechanisms of the drugs used in the treatment of depression are generally multiple

and finally, in most cases, we do not know precisely what makes the effectiveness of a treatment”, he explains.

Ultimately, debates over the role of serotonin only illustrate how

it is difficult to understand the biological and social mechanisms of a disease

as complex as depression, which forces researchers to rely on models that are inherently incomplete. “We stick to hypotheses and we continue to seek and test models against each other”, concludes Johanna Hofmann.

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