All the questions the doctors examined the health of children, none has been more thoroughly researched than the question of whether vaccines are associated with autism. After hundreds and hundreds of studies on thousands of children, “we can say with almost the same confidence than anyone could say that vaccines do not cause autism,” Mayo clinic researcher of autism, Dr. Sunil Mehta told me.
And the fear that they are still stubborn as 2017 Measles outbreak in Minnesota shows. The virus has spread among unvaccinated children — in this case Somali-Americans in Minneapolis, after the anti-vaccine advocates focused on parents who were concerned about autism disinformation campaign. By the end of the outbreak in August last year, 79 people, most of them children, came down with the measles.
Today, about one in 68 children in the United States of autism — this figure has remained unchanged since at least 1990, although there has been an increase in the awareness and diagnosis. And it’s families raising children with autism, which are among the most active supporters of the vaccine-autism link. Many are confused and looking for an explanation about why their children have developed it.
It doesn’t help that doctors have long struggled to explain what causes autism. For many years, and many medical theories were debunked, and then replaced with new ones.
But the medical community is now getting closer and closer to zeroing in on the cause. I recently talked to a dozen scientists at the forefront of this work to find out what they see as the latest and best evidence for what may cause autism. They were delighted with their new understanding of the genetic basis of autism — that they are considered as the most promising area of research right now. They also spoke about the latest advances in the understanding of how certain genetic mutations change the biology of the brain so that cause the symptoms of autism.
More blurry conducts its research work on non-genetic (or environmental) participants with autism, as pollution or drugs. Here is a brief description of what we know about the causes of autism — from the good to the not less well-established.
The strongest evidence of causes: genetics
Autism spectrum disorder is a collection of almost 1000 different conditions, with symptoms ranging from delayed speech development to anti-social behaviour and repetitive movements.
But “of all the causes of autism, which we know with certainty that it is a genetic disease,” said University of California geneticist and researcher of autism Stephan Sanders. “If you look at a child with autism, look at your brothers and sisters, you will find the level of autism is 10 times higher in those children than in the General population. It was looked at in the populations of millions.”
Researchers first recognized the genetic basis of autism in the 1970’s, with studies on twins with the participation of at least one brother with him. They found that in monozygotic twins (with almost the same genetics) was more likely to have autism in common than dz (or nonidentical) twins, who share a common genetically.
Since then, large-scale population study found the same pattern — and the researchers came to the view that common genetic variants in families is probably more important than shared environments to start ball benefiting.
“The point is that when you add up all the genetic risks, it seems that genetics can account for 50 percent of the risk for autism that is very high,” said David Amaral, autism specialist at the University of California Davis against the institution. To put that into context against other common health problems, like heart attacks or cancer — autism is more genetic, more than 100 genes now involved.
Now the big question is how these genes affect the brain in such a way that leads to the symptoms of autism. So the next frontier in this area of research autism the understanding of the biological effects of autism genes (or genes in which mutation increases a person’s risk of developing it).
“We expect some commonality in the consequences of the [autism] genes, which we hope will reflect the most important aspects of the biology of autism,” said Sanders. To put the puzzle pieces together, on the underlying biology of autism will help researchers to focus on potential therapies, he added.
To get there, the researchers used polnocennogo sequencing. The technique has been transformative of autism research because it allows researchers sequence human coding genes or a small percentage of DNA in the genome that are translated into proteins, making the functioning of genes and see how the exomes of people with autism differ from those without it.
Through eczane sequencing, Sanders and his colleagues found that genetic variation in the gene SCN2A are associated with autism. Based on this discovery, they were able to uncover the “Rosetta stone” of pathology in autism: specific genetic defects in individual neuronal proteins that lead to either epilepsy or autism, depending on how the mutation worked on protein.
Narrowing of how these genetic mutations can cause autism or other health problems, opens the door to a better understanding of biology and how to treat it.
It is worth noting that while there is a robust conversation about finding ways to treat autism, there is also a growing conversation in the autism community by rejecting the language of “disease” and “treatment” and focusing on acceptance of autism and neurodiversity.
Exposure to infections and certain medications during pregnancy may be associated with autism
Not everyone with these genetic mutations autism — this is because researchers believe it is not only mutations that cause it.
In many cases it is necessary that an underlying genetic predisposition or mutation face a number of potential environmental triggers. And to find the environmental risk factors, where things get muddy very quickly.
Researchers have proposed dozens of potential environmental contributors to autism, including air pollution, pesticides, antidepressants and viruses. And few of them have very reliable science behind them, largely because it is much more difficult to confirm environmental causes of the disease.
“On the environmental side, nothing has come close to that level of confidence we have in the genetic causes of autism, partly because it is so hard to do experiments,” concluded Sanders.
In General, however, researchers have identified potential links between brain abnormalities in children with autism and certain triggers during fetal development.
For example, there is pretty convincing evidence linking a mother’s infection with the rubella virus during pregnancy with an increased risk of autism in her child. The evidence for other viruses, such as influenza or herpes — however, much less clear. “Some studies show some associations between diseases and autism], but not others,” explained Dr. Alice KAU, Director of the program for the study of autism at the National Institute of health. “Results are mixed”.
There is quite convincing evidence that the mother’s use of the drug thalidomide (originally used for morning sickness and now used to treat multiple myeloma and other diseases) and Valproic acid (for epilepsy and seizure control), it seems to put children at increased risk of developmental disorders of the nervous system, including autism.
But the evidence is mixed again on other drugs and supplements such as SSRI antidepressants and folic acid.
It is also mixed when it comes to stress. Researchers have long known that stress during pregnancy is associated with low fertility and even premature birth. They also study how susceptibility to stress — traumatic or extremely stressful life events during pregnancy can contribute to autism, but they never came to any concrete conclusions.
Despite all assertions to the contrary, the same remains true for heavy pesticide exposure and air pollution. You can find studies supporting and debunking these links and there is little agreement among researchers.
One of the reasons for the different results is that there’s not always a simple linear relationship between exposure to specific environmental trigger and the risk of autism. Genes also play a role here. And to understand how pollution or pesticides could lead to autism (or not), the researchers also need to understand how a person’s genetics determines how well their body metabolizes the chemicals react to stress, and any number of other possible attacks.
This is the next frontier in this area of research autism, said University of California geneticist Lauren Weiss. For example, in a recent study, Weiss and her co-authors examined whether genetics affects the levels of chemicals circulating in the mother’s blood during pregnancy and thus potentially the risk of her child autism.
“Some of the strongest links between autism and lower levels of chemicals in the [mother’s] blood, and we think that suggests that it is not a causal relationship,” explained Weiss. “It may be, as the body can handle chemicals that determines how much circulates during pregnancy”.
In other words, the mother’s genetics affects how it responds to chemicals, and in turn, how they affect her fetus. And this is where research is conducted: “autism research increasingly needs to combine the collection of genetic data with estimates of environmental risk,” said Amaral.
Researchers agree the mmr vaccine does not cause autism, but the evidence is not sufficient for other triggers after birth
Overall, the evidence for this prenatal exposure is stronger than the evidence for a range of postnatal factors that may cause autism, Amaral said.
As he wrote in a recent review on possible causes of autism“ because autism is a neurological disorder that reflects an impaired function of the brain, it is possible that the stroke occurs after birth.” But, he added: “currently there is very little evidence for this.”
One of the most popular theories — that the Measles, mumps and rubella can cause autism — has been debunked as the result of large-scale studies involving thousands of participants in different countries.
Other popular potential postnatal causes, such as deep social exclusion among children, is also not disputed.
“Although we are still in this grey zone, trying to find a more specific cause of autism, almost all causes occurs prenatally,” said Amaral. “If you have autism, you’re probably born with it.”
Boys are more likely to be autistic than girls
There is another important conclusion about autism: it seems to affect boys four times more than girls.
The researchers found that it takes fewer genetic mutations for boys to get autism than girls, and they call it a “female protective effect.” This means that for some reason girls with several autism-related genetic mutations would be able to adapt to the fact that the genetic hit — without identifiable autism-like behaviors, while many young boys may not.
The scientific community does not understand how it works. But scientists are trying, because it can help them to determine the biological treatments of autism.
There are also some studies that show autism may be harder to detect in girls, so women may be under-diagnosed. Autism researchers are working to unpack these subtle differences. Again though, this is not the cause of the disease — just the Association with the female sex.
The lack of iron-clad autism causes may be why people are exposed to the autism-vaccine hypothesis. It is much clearer than the explanation, assuming that it is the result of some murky genetic-environmental interactions.
This time, it will take time for researchers to reveal biology of autism and how genetics and environment work together to determine the risk of autism. There is also new evidence that the gut microbiome communicates with the brain to promote the characteristics of autism, which further complicates our understanding of autism, says Amaral. But scientists are quickly moving towards clearer answers — and maybe even biological treatment methods (for which currently there are).
Now vaccines are the wrong explanation of autism, and we have to give the idea. Researchers of autism. The more we hold on to it, the more flares we will see a Measles outbreak in Minnesota, where the fears of the autism community has embraced and pushed them away from life-saving vaccines.
Sourse: vox.com
