How Do People Get Autism

Understanding Autism Spectrum Disorder

Autism Spectrum Disorder (ASD) is a complex developmental disorder that affects communication and behavior. It's characterized by difficulties with social interaction, verbal and nonverbal communication, and repetitive behaviors. The process of understanding how people develop autism involves looking at both genetic and environmental factors.

Screening for Autism

The American Academy of Pediatrics (AAP) recommends that all children be screened for autism at ages 18 months and 24 months. This is in addition to developmental and behavioral screenings during their regular well-child visits at 9 months, 18 months, and 30 months. Notably, by age 2, an ASD diagnosis by an experienced professional can be considered reliable. This underlines the importance of early detection and intervention in managing ASD.

Brain Development in Autism

Research has found links between ASD and abnormal brain development. Specifically, abnormal brain overgrowth occurs during the first 2 years of life in children with autism. By 2-4 years of age, the most deviant overgrowth is in cerebral, cerebellar, and limbic structures that underlie higher-order cognitive, social, emotional, and language functions. Moreover, this excessive growth is followed by abnormally slow or arrested growth.

This unusual pattern of brain growth is one of the most crucial signs of ASD and can be used to understand why individuals with autism exhibit certain behaviors. However, further research is needed to fully understand the link between abnormal brain development and the onset of ASD.

The process of diagnosing and understanding ASD is complex and multifaceted. It involves not only recognizing the symptoms and behaviors associated with the disorder, but also understanding the underlying genetic and environmental factors that contribute to its development. The following sections will delve deeper into these factors, providing a comprehensive look at how people develop autism.

Genetic Factors in Autism

While the exact cause of autism spectrum disorder (ASD) remains unknown, most researchers agree that genetics play a significant role in the development of the condition. This section seeks to elucidate the role of genetics in ASD, genetic syndromes associated with ASD, and the recurrence risk and heritability of the condition.

Role of Genetics in ASD

According to the Centers for Disease Control and Prevention (CDC), most scientists concur that genetics impact the likelihood of developing ASD. The interplay between genetics and environmental factors is complex, with research suggesting that around 102 different genes may contribute to the likelihood of being born with autism [3].

Furthermore, research indicates that 60-90% of the risk for autism comes from one's genome, with changes in certain genes or the genome itself increasing the chances of a child developing autism.

Genetic Syndromes and ASD

In some cases, a high risk for Autism Spectrum Disorder (ASD) can be associated with genetic disorders like Rett syndrome or fragile X syndrome. However, the majority of autism cases result from multiple changes in different regions of DNA, working in conjunction with various genes and environmental factors.

This highlights the multifactorial nature of ASD, where a combination of genetic mutations and environmental exposures can contribute to the development of the condition.

Recurrence Risk and Heritability

The recurrence risk of autism in siblings of children with the condition is between 2% and 8%. This risk increases to between 12% and 20% if the siblings show impairment in one or two of the three domains typically impaired in autism.

Heritability estimates suggest that autistic traits in the general population are highly heritable, ranging from 40% to 80%. This suggests a strong genetic component in the development of autism, further emphasizing the significant role of genetics in ASD.

Understanding the genetic factors associated with ASD is crucial to informing personalized interventions and providing a foundation for future research into the causes of autism.

Environmental Factors and Autism Risk

When investigating 'how do people get autism', it's vital to consider the role of environmental factors. While genetics play a significant role in autism spectrum disorder (ASD), research has suggested that several environmental influences may also contribute to the risk of developing autism.

Environmental Influences on ASD

Environmental factors play a significant role in autism risk. Studies have suggested that prenatal exposure to certain medications, socioeconomic status, drug use, toxic exposure, and gene-environment interactions can all contribute to ASD risk.

One of the environmental factors that has been linked to autism is exposure to certain chemicals and pollutants. These include air pollutants, pesticides, hazardous chemicals, flame retardants, and phthalates. Research has found that children exposed to higher levels of these pollutants before and after birth were more likely to develop autism.

Maternal Factors and Autism Risk

Maternal factors, particularly those that occur during pregnancy, can also affect the risk of autism. Studies have shown that parental exposure to heavy metals and other environmental toxins during pregnancy can increase the likelihood of a child being born with autism. Certain prescription drugs used during pregnancy, such as valproic acid and selective serotonin reuptake inhibitors (SSRIs), have also been linked to an increased risk of ASD.

Another maternal factor that has been associated with an increased risk of autism is age. According to the CDC, children born to older parents are at a greater risk of developing autism.

Postnatal Risk Factors

In addition to prenatal and maternal factors, certain postnatal environmental influences can also contribute to the risk of autism. Viral infections and metabolic imbalances that occur during the early stages of life have been associated with an increased risk of autism [3].

Furthermore, exposure to certain environmental toxins and pollutants after birth, such as air pollutants, can also increase the risk of autism. As per research, children exposed to high levels of these pollutants after birth were more likely to develop autism [6].

Understanding the environmental factors that can contribute to autism risk is crucial for autism prevention and early intervention strategies. By identifying and managing these risk factors, it may be possible to reduce the incidence of autism and improve outcomes for those who are affected.

Complex Causes of Autism

Unraveling the complexity of autism involves understanding the interaction of genetic and environmental factors. The multifaceted nature of this condition continues to challenge the global scientific community.

Genetic and Environmental Interplay

Autism is regarded as a highly genetic disorder, with various genetic changes causing autistic symptoms. Mutations in genes like NLGN3, NLGN4, NRXN1, CNTNAP2, and SHANK3 have been identified as causes of autism, mental retardation, and other neuropsychiatric syndromes.

Interestingly, mutations associated with autism often occur de novo, meaning they are present in the child but not in the parents or earlier ancestors. This is due to negative evolutionary selection, where affected individuals have decreased fertility, leading to mutations frequently occurring as de novo mutations.

Up to 7%–10% of children with autism have de novo chromosomal deletions and duplications, which typically cause a spectrum of phenotypes that include autism. Specific genes like NLGN3, NLGN4, NRXN1, CNTNAP2 have been implicated in autism and are associated with synaptic functions [7].

However, genetic factors alone do not fully explain the onset of autism. Researchers believe environmental influences also play a significant role. Although the exact environmental factors that contribute to autism are still being explored, they may include prenatal and perinatal complications, parental age at conception, and certain maternal lifestyle factors.

The complex interplay between genetics and environment makes it challenging to pinpoint the exact cause of autism in each individual. More research is needed in this area to gain a better understanding of the intricate mechanisms underlying autism.

Pervasive Developmental Disorder

Autism is classified as a pervasive developmental disorder. This means it affects many aspects of cognition and behavior, and symptoms emerge during development from infancy or perhaps from birth.

The primary lesion causing autism is a key question, with recent findings suggesting that some behavioral or neurobiological defects can improve after development is largely complete. This indicates that autism may be more of a disorder of late postnatal development, plasticity, or even adult function as opposed to a condition that is purely predetermined by genetics or early developmental factors.

The recurrence risk of a pervasive developmental disorder in siblings of children with autism is 2% to 8%, rising to 12% to 20% if siblings show impairment in one or two of the three domains impaired in autism. Heritability estimates suggest that autistic traits in the general population are highly heritable, ranging from 40% to 80%.

These findings underscore the complex and multifactorial nature of autism, emphasizing the need for a nuanced understanding of the disorder. Ongoing research continues to shed light on the causes of autism, providing valuable insights that can guide future treatment and intervention strategies.

Early Signs and Symptoms of Autism

Recognizing early signs and symptoms of autism spectrum disorder (ASD) can make a significant difference in a child's development. These symptoms often manifest as developmental differences and delays in joint attention.

Developmental Differences

Children on the autism spectrum may show delays in spoken language or differences in how they interact with peers. Despite these differences, these children typically reach physical developmental milestones, such as sitting, crawling, and walking, on time. Subtler differences in the development of gestures, pretend play, and social language often go unnoticed by families and doctors.

Almost all children on the autism spectrum show delays in nonverbal communication and spoken language. For example, they may use words to label things but not to ask for things, repeat what they hear for a longer period, or talk more like an adult than a toddler. Additionally, about 25% of children later diagnosed with ASD may develop some language that they suddenly or gradually stop using, typically between the ages of 15 and 24 months. This change, known as a regression in skills, might also make them become more socially withdrawn [8].

Delay in Joint Attention

One of the most important developmental differences between children on the autism spectrum and children without ASD is a delay in or lack of joint attention. Joint attention, which is a building block for later social and communication skills, refers to the shared focus of two individuals on an object or event. For example, a child might make eye contact with a parent and then point to a toy to share enjoyment of it. For children on the autism spectrum, this type of interaction can be challenging [8].

Acting early upon concerns about how a child plays, learns, speaks, acts, or moves can make a big difference in their development. If there are any concerns about a child's development, it is recommended to talk with a pediatrician.

Understanding these early signs of autism helps in early diagnosis, which allows for timely intervention and better management of this complex developmental disorder.

Advances in Autism Research

Research into the causes and development of Autism Spectrum Disorder (ASD) has made significant strides in recent years. This has been largely driven by advances in genetic studies, which have shed light on the role of genetic variations in the development of autism.

Genetic Studies and Autism

Scientific studies have demonstrated that autism is a highly genetic disorder. Various genetic changes can cause autistic symptoms, with mutations in genes such as NLGN3, NLGN4, NRXN1, CNTNAP2, and SHANK3 identified as causes of autism, mental retardation, and other neuropsychiatric syndromes.

Up to 7%–10% of children with autism have de novo chromosomal deletions and duplications. This typically causes a spectrum of phenotypes that include autism. Specific genes like NLGN3, NLGN4, NRXN1, CNTNAP2 have been implicated in autism and are associated with synaptic functions [7].

Impact of Genetic Variations

Mutations associated with autism often occur de novo, meaning they are present in the child but not in the parents or earlier ancestors. This is due to negative evolutionary selection, where affected individuals have decreased fertility, leading to mutations frequently occurring as de novo mutations.

Remarkably, recent studies have shown that some animal models of autistic symptoms have demonstrated a surprising degree of reversal or amelioration of symptoms by replacing or modulating gene function after birth or even in adulthood. Examples include Drosophila models of Fragile × syndrome and mouse models of Rett’s syndrome, where symptoms were partially or seemingly completely resolved by reinstating the MeCP2 gene after birth.

The female sex is suggested to be protective towards ASD susceptibility, with studies showing that the average mutational burden in diagnosed females is much higher than in males. However, there may also be male-specific vulnerabilities, with males generally having a higher expression of genes implicated in ASD. The reasons for the sex bias in ASD rates are not yet completely clear [9].

These findings underscore the complexity of autism and the myriad ways in which genetic factors can influence its development. As our understanding of these genetic variations and their impacts continues to grow, so too does our potential to develop more effective strategies for diagnosing, managing, and potentially even preventing autism.

References

[1]: https://www.autismspeaks.org/signs-autism‍

[2]: https://pubmed.ncbi.nlm.nih.gov/15362165/

‍[3]: https://www.healthline.com/health/autism-risk-factors

‍[4]: https://www.autismspeaks.org/what-causes-autism

‍[5]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3513682/

‍[6]: https://sparkforautism.org/discover_article/environment-autism/

‍[7]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2701104/

‍[8]: https://www.healthychildren.org/English/health-issues/conditions/Autism/Pages/Early-Signs-of-Autism-Spectrum-Disorders.aspx

‍[9]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6710438/