Why Autism Spectrum Disorder Occurs?

The “disorder” is the function of an abnormality of an organism or an irregular function. Generally, it is divided into 5 main categories which are mental illnesses, physical disorders, genetic disorders, emotional and behavioral disorders, and functional disorders.

It is possible to draw all the disorders on the same base in biochemical and molecular dimensions. Each living consists of atoms and has a certain biochemical structure. Therefore, the interactions between these organisms, substances, and energies may have negative consequences in one or more of the organisms. These negative results are seen as “disorder” in individuals.

Disorders can occur in many different ways with very different elements. They can also occur without a direct physical or chemical interaction. In today’s world, we say that a lot of reasons can cause lots of different diseases and disorders. They could be genetics, environmental factors, neurodevelopmental impairments or toxins.



In this article, I will try to explain why Autism Spectrum Disorder occurs. Firstly, I will clarify the symptoms of that disorder. Secondly, contributions to it will be clarified. And then, I will move on to reasons for having ASD which would be mostly genetic ones, but also I will try to explain all the causes which scientists investigate.   

Autism Spectrum Disorder (ASD)


Autism Spectrum Disorder is a broad term used to describe a series of neurodevelopmental disorders characterized by communication and social interaction problems. There are many subtypes of autism and each individual with autism may have specific strengths and also weaknesses. Genetics and environmental affect the development of ASD. This disorder is often accompanied by medical problems such as gastrointestinal disorders, seizures, and sleep problems.   

Autism Spectrum Disorder can be difficult to diagnose. This disorder has a number of symptoms rather than a single symptom. And its severity can vary greatly from person to person.  

Symptoms of ASD occur in children before the age of 3, but sometimes the diagnosis can be made after 3 years of age. It affects an estimated 1 in 110 children and is 4 times more common in boys than in girls. 



There are many causes of autism and it is also thought to have a genetic predisposition. Although it is a disorder difficult to diagnose, there are some main symptoms which are listed below.

•    Problems related to language development

•    Unable to have eye contact and common attention issues

•    Face recognition and emotion recognition problems

•    Inability to use and to understand gestures

•    Not showing interest to peers

•    Lack of imitation skills

•    Having no interest in the functioning of objects

•    Echolalia

•    Limited and repetitive behaviors

Why Autism Spectrum Disorder (ASD) Occurs? 


Autism, which is a developmental disorder, contrary to what has believed it is not complete mental retardation. Children with autism, whose numbers are growing with each passing day, have common difficulties in perceiving the world, but with early diagnosis, special education, and treatment, they can live as normally developed people. 



Here again, conscientious and self-sacrificing parents need to be at work. Most individuals with autism always have difficulty in communicating with people. However, early diagnosis and treatment would be effective in reducing this communication difficulty. 

When the parents realize the symptoms of Autism Spectrum Disorder in their own child, they start the question of the reasons. They immediately ask “why autism occurs?”. Parents give an answer to this question abstractively. These answers could be;   

•    Firstly electronic devices come to minds such as television, phone or tablet. They asked themselves that “while I feed her, I forced her to watch TV. Could it become because of that?”

•    “Nany put her in front of the TV while doing housework. Perhaps it happens because of that?”

•    “ When the sister is born, his speech has regression. Maybe he got cross with us?”

•    “ I think he is aware of everything but he is stubborn. His father is also stubborn. He should take after his father.”

•    “Are there any ingredients in ready-made food which causes this?”

•    “I was working and did not take care of him. Could it be because of that?”

•    “We are already calm family. There would be no noise in our home. Also, we would have little or no guests. Could it be the reason?”

•    “School harassment?”

•    “Can vaccines be caused in order to have it?”  



These questions and thoughts have no ends and they continue. In fact, science has not found the exact cause, yet. However, the most common opinion is that it is a genetic and neurological disorder. Especially according to some recent results, there are some opinions about this issue.

•    Autism Spectrum Disorder occurs as a result of the combination of negative sides of genetics, biological and environmental factors. Since the beginning of the first months of the baby, it is a structural disorder due to abnormal growth in the mirror neurons in the brain.

•    Autism Spectrum Disorder occurs as a result of abnormal functioning of neurotransmitters such as serotonin, dopamine, and epinephrine. Some scientists interpret this as a reaction of the body against a virus. A viral cause can also trigger this problem which is having autism.

•    Autism Spectrum Disorder occurs because of gene change and mutation. If the child has a genetic predisposition, environmental and biological effects can cause having autism.

•    Autism Spectrum Disorder occurs as a result of high exposure to pesticides and air pollution during a mother’s pregnancy. 

However, these are still in the theory phase and the current one is not found, yet. It has been reported that having autism has increased 10 times in the last 40 years. It is also emphasized that the number of having that disorder is increasing between 10% and 17% on an annual basis.



An individual with Autism Spectrum Disorder may face challenges in communication, social understanding, social interaction, repetitive behaviors, sensory sensitivities, or any number of other areas. It is rare for two people with ASD to have the exact same combination of symptoms. Why does it occur like that? One proposed explanation is that autism is caused in different ways in different people who then end up with a slightly different version of ASD. There are several kinds of genetic factors that may contribute to autism, And also, it is possible a variety of environmental factors play a part as well. In fact, the “TRIPLE HIT HYPOTHESIS” proposes that ASD is caused by 3 main factors.

1)    an environmental stressor interacting with (external factor a person encounters, such as a pesticide, a virus, or a medication)

2)    an underlying genetic vulnerability (one or more genes which may turn “on” or “off” )

3)    at a critical moment of brain development.  



Scientist proposed many causes of Autism Spectrum Disorder, but an understanding of the theory of causation of autism is incomplete. Research indicates that genetic factors predominate. The heritability of autism, however, is complex, and it is typically unclear which genes are responsible.

Autism Spectrum Disorder is mostly a genetic disorder, according to researchers. However, genetic reasons are not sufficient in order to explain all cases. Among the environmental risk factors, the most prominent ones are the advanced age of the parents, the lack of oxygenation of the baby at birth and the lack of vitamin D.  

DNA is a major force in the development of Autism Spectrum Disorder in a child, but as I mentioned before, it is obviously not the only one. Think about research on identical twins, who have identical genes. Usually, if one identical twin has autism, the other twin has too. But it does not mean that it should be like this all the time. Even they both have autism, we can not presume that they share the same severity of . Because, two identical twins are known to be different in a number of illnesses and disorders, but of course the symptoms would be different than each other.



Epigenetic changes or environmental factors could help explain those differences. These factors could be twins’ competing for nutrition in the womb or having different environmental exposure after birth. Scientists are only beginning to understand the complex interaction of our DNA, the environment, and epigenetics.  

After those developments, in scientific studies examining the relationship of autism with genes, scientists stated that while there may be a relationship between the new mutations that occur in different genes and the problem, brain imaging studies also revealed many interesting findings of this issue.

A mutation that affects chromatin, which is the complex of DNA and proteins that make up our chromosomes, could affect the expression of thousands of genes. And in which it could increase the risk of having Autism Spectrum Disorder. Scientists are not sure about whether this risk is related to specific pathways being perturbed or just general confusion of the cells.   

According to some studies, children with a genetic mutation linked to ASD may have been more susceptible to infections their mothers experienced while pregnant with them. Those children with autism have more severe social communication problems and repetitive behaviors than other children with autism, who did not have those risk factors. However, this apparent interaction between genes and prenatal infections did not affect the children’s learning and everyday living skills.



In general, many different prenatal conditions and events could be involved in the reasons for having autism. It is difficult to sort out what factor is causing which effect.

The blood test is not enough for the investigation of autism. Because it can not say what is in the brain and autism is a neurological disorder which up to brain impairment. That is the reason researchers start to use brain imagining in order to understand how different brain cells have different epigenetic profiles in every individual. It is important to study the brain directly. By studying brain tissue, scientists discovered that genes with different methyl tags in the brain’s cortex affect the way cells talk to each other, among other things.

In other respects, researchers found that there is a link between having a less than optimal pregnancy and/or birth in a general and a higher risk of autism. Less than optimal refers to a variety of circumstances such as being born feet first, Cesarean delivery, “fetal distress,” or prematurity. It is clear from reviewing many studies, all done in different ways and each with its own shortcomings, that we still have few concrete answers.



Even studies that have shown a certain factor may be associated with risk for ASD have generally not been able to clearly explain the underlying mechanism. This underlying mechanism could be how the factor biologically leads to the development of autism.

In addition to those, some studies by pointing out that there is a close relationship between the microbes in the intestine, brain development, functions and immunity, the scientist stated that this subject is actively investigated in autism spectrum disorder cases, but the changes in the intestinal flora cannot be fully demonstrated.

Furthermore, there is clear evidence that specific drugs taken during pregnancy are associated with an increased risk of having autism. Thalidomide, which is given to treat morning sickness, but was banned because it led to all kinds of birth defects. It has been associated with autism, as have valproic acid and other anti-seizure medications taken during pregnancy.



According to some studies that have been done with mice, the prenatal viral infection is called the main non-genetic cause. Exposure to rubella activates the mother’s immune system. This can greatly increase the risk of having it in mice. Congenital rubella syndrome is the most convincing environmental cause of autism.

On the other hand, as maternal infections, there have been many studies about the relationship between having ASD and a variety of other infections. Maternal infections that are happened during pregnancy. These infections could be toxoplasmosis, cytomegalovirus, and herpes. If it occurs in the second half of pregnancy-associated with a modest increase in the risk of having a child with autism, particularly when a bacterial infection occurs.

It has been proposed by researchers, it may be a mother’s immune response rather than a specific infection that is linked with vulnerability to ASD. In this case, it would be the reaction of a mother’s body as it tried to fight an infection, rather than the infection itself, that caused a problem.

As conclusion, learning how the environment, epigenetics, and genes interact in order to influence Autism Spectrum Disorder could answer many questions about how it develops and why it looks different in each individual.

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