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19 avril 2012 4 19 /04 /avril /2012 12:08

Des chercheurs américains ont identifié dans le sang des marqueurs biologiques de la dépression chez l'adolescent, ouvrant la voie à une nouvelle méthode de diagnostic rapide.

 

La dépression sera-t-elle un jour diagnostiquée aussi simplement que le diabète ou le cholestérol, par un simple test sanguin? 

 

C'est en tout cas l'espoir que fait naître une étude américaine réalisée sur des adolescents dépressifs et publiée cette semaine dans la revue Translational Psychiatry .

 

Le diagnostic de la dépression se fait aujourd'hui sur des critères subjectifs, qui sont liés à la capacité du patient à raconter correctement ses symptômes et dépendent aussi de l'aptitude du médecin, qui n'est pas forcément un spécialiste lors de la première consultation, à les interpréter. 

 

La distinction entre la forme dite majeure de dépression, celle qui est la plus grave et de simples vagues à l'âme est aussi importante, et pourrait éviter la prescription de nombreux médicaments antidépresseurs inutiles.

 

«Le diagnostic de la dépression chez les adolescents est compliquée par le fait qu'elle peut se cacher derrière des troubles bien plus variés que chez l'adulte, allant des difficultés scolaires à des fugues en passant par la prise de drogues», précise le Dr Alain Braconnier, psychiatre spécialiste de la dépression chez les jeunes.

 

Les chercheurs ont réalisé des tests sanguins à l'aveugle sur 14 adolescents déjà diagnostiqués avec une dépression majeure, et 14 autres non-déprimés, tous âgés de 15 à 19 ans. 

 

Les recherches ont été focalisées sur 26 marqueurs génétiques présents dans le sang et déjà identifiés comme caractéristiques d'états dépressifs sévères lors d'études menées sur des rats.

 

Une fiabilité élevée

 

Onze des marqueurs choisis ont permis de faire la distinction entre les jeunes déprimés et ceux en bonne santé, avec un niveau de fiabilité plutôt élevé. 

 

«Ces 11 gènes ne sont probablement que le haut de l'iceberg car la dépression est une maladie complexe, mais cela indique clairement que nous pouvons créer un test sanguin de diagnostic pour la dépression», affirme Eva Redei, psychiatre à la Northwestern University à Chicago (États-Unis) et auteur principal de l'étude.

 

De manière totalement isolée, une entreprise privée, Ridge Diagnostics, travaille également à la mise au point d'un test sanguin pour la dépression, et a obtenu des résultats prometteurs sur 70 adultes.

 

Le spécialiste français Alain Braconnier estime que des tests biologiques ne sont pas forcément indispensables, et ne pourront de toute façon se substituer à un examen clinique, mais il reconnaît «qu'ils pourraient être utiles dans des cas très difficiles où l'on peut hésiter beaucoup entre deux conditions.»

 

L'étude sur les adolescents présente la particularité de pouvoir distinguer deux sous-types de dépression, entre les patients souffrant seulement de dépression et ceux qui souffrent aussi de troubles anxieux. 

 

«C'est une première étape qui va nous permettre de voir quel traitement sera le plus efficace pour un patient donné», précise le Dr Eva Redei, qui veut poursuivre les tests sur un échantillon plus grand et plus varié.

 

Cyrille Vanlerberghe - le 18/04/2012

 

Researchers Develop Blood Test for Depression

Group of biomarkers accurately identified teens with mood disorder in small study

 

TUESDAY, April 17 (HealthDay News) -- Researchers have developed a blood test that could one day help diagnose teens with depression.

 

To create the test, researchers identified 26 potential biological markers for depression

Then they tested the markers in a small group of teens and found that a handful of them could distinguish the teens with major depression from those without depression.

 

The research was published April 17 in the journal Translational Psychiatry.

 

"I think it would be more accurate to diagnose depression with a blood test," said study author Eva Redei, a professor of psychiatry at Northwestern University Feinberg School of Medicine. The biomarkers now have to be studied in a larger group of teens, she added.

Currently the diagnosis for depression is subjective and involves doctors talking with patients about their moods. The evaluation is especially tricky in teens because this is a trying time emotionally to start with, Redei said.

Having an objective diagnosis that relies on biomarkers could also make it an easier diagnosis for teens to hear and ease some of the stigma associated with depression.

 

"It would bring this disease into the same family of other serious illnesses," Redei said. "It would be much more difficult for somebody to say, 'Just snap out of it' or 'Get yourself together.'"

Between 17 percent and 25 percent of adolescents and young adults experience depression, according to study background information. 

 

Teens who develop depression have a worse prognosis, marked by illness, substance abuse and suicidal behavior, compared to people who are diagnosed later in life.

 

The current study involved 28 white and black teens in the Chicago area. Half of the teens had depression.

 

The researchers compared the levels of the 26 potential biomarkers in blood samples from the teens and found that 11 of them were present at higher or lower levels among the teens with depression.

 

In addition, they found that 18 of the biomarkers could accurately predict whether teens with depression also had an anxiety disorder.

In a clinical setting, a screening test for depression would involve a panel of biomarkers, Redei explained. Some of them would give the doctor a yes/no answer about whether the teen could have depression and should be further evaluated, while others could reveal information about the depression and how to treat it, such as its severity and whether it is accompanied by anxiety.

 

"The hope is that not only can these tests identify who is depressed, but they also potentially discriminate between different types of depression," Redei said.

 

But first Redei's group has to determine whether their biomarkers are accurate in a large group of teens representing a range of racial backgrounds and from different areas of the country. They are now beginning these studies.

 

Larger studies will tell us a lot about how useful these biomarkers could be, said Dr. Sheldon Preskorn, a professor of psychiatry at the University of Kansas School of Medicine-Wichita. Anytime you test a number of potential biomarkers on a small group of people you are going to find some biomarkers that look clinically important, he added.

 

But having a screen to help identify who has depression could be hugely helpful, Preskorn said. "This kind of approach is somewhat the holy grail of psychology."

 

There are as yet no biomarkers available for diagnosing depression at any age.

 

Redei's group is also testing the biomarkers in adults. Although it is too soon to tell for sure, she thinks that some will end up being helpful for diagnosing depression in adults.

 

The group originally identified the set of 26 candidate biomarkers by studying rats with conditions that mimic depression in humans. And like in humans, the condition in rats is linked either to genetic or environmental factors.

 

The researchers looked in these animals at a type of molecule called a transcript, which is an intermediate molecule between a gene and its corresponding protein. Differences in the level of transcripts indicate changes in gene expression.

They found 11 transcripts that were different in the blood and brain of animals that were bred to be in a perpetual state of depression compared to normal animals. In addition, they found 15 transcripts that increased or decreased in groups of rats with environment-induced depression.

Altogether the changes that the researchers found were in genes that were "most unexpected," Redei said, adding that, "This just characterized how little we know about depression."

 

The discovery of these biomarkers gives researchers a new list of targets to pursue as potential antidepressants, Redei said.

 

Having a reliable blood-based diagnostic for depression could also open the door to treating people before symptoms appear, Preskorn said. 

 

"You might want to look at high-risk populations, like if you have a family history of depression."

This approach is similar to how doctors manage other conditions like heart disease, Preskorn said. "If you know that a person has high cholesterol and high lipids, then you don't wait till the person develops atherosclerosis to start the statin drug."

 

 

More information

You can learn more about diagnosing depression at the U.S. National Institute of Mental Health.

SOURCES: Eva Redei, Ph.D., professor, psychiatry and behavioral sciences, Northwestern Medicine, Chicago; Sheldon Preskorn, M.D., professor, psychiatry, University of Kansas-Wichita School of Medicine and chief scientific officer, clinical trial unit, University of Kansas Medical Center; April 17, 2012, Translational Psychiatry

Last Updated: April 17, 2012

 

By Carina Storrs
HealthDay Reporter


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