Scientists and researchers are still working to understand the complex causes of autism spectrum disorder (ASD). Current findings suggest that autism is not the result of a single factor but rather a combination of influences. These include genetic predispositions, physical conditions, and environmental factors that interact in unique ways.
Understanding the causes of autism is essential for early detection and support. If you’d like to learn more, download our free guide to explore the latest insights:
Risk factors and possible causes of autism
Is autism genetic? Studies have shown that a child can be genetically predisposed to ASD. This means that the genes inherited from the child’s parents make them likely to develop autism.
However, it is a misconception that autism is caused by genes alone. In most cases, the genetic factor needs to be triggered by an environmental factor to develop autism spectrum disorder.
While we now know there is not a single cause for autism, it is also important to recognize the multiple risk factors that can contribute. Some of the factors include:
- Genetics
- Sibling connection
- Older parents at conception
- Environmental factors
- Biological causes
- Abnormal digestive conditions
Genetic causes of autism
People with certain gene variations are said to be likely to develop autism. These genes are believed to affect brain development.
People with genetic disorders such as the Fragile X syndrome are at high risk for developing autism. The syndrome, which causes learning disabilities, is one of the many gene abnormalities that can cause autism.
To date, scientists have identified 30 genes involved in the risk of developing autism. Most of these genes are responsible for brain growth.
However, after decades of scientific research, scientists are not able to identify one genetic trait that is common in every person with autism.
Is autism hereditary?
Some forms of autism are believed to have a genetic basis, which means autism can sometimes run in families. For instance, twins often share a higher likelihood of both being autistic, and siblings born a few years apart may also exhibit autism traits.
Observations over time have highlighted that identical twins tend to have greater similarity in autism characteristics compared to fraternal twins, reinforcing the idea of a hereditary connection.
Autism is widely recognized as a heritable condition, with family patterns suggesting a genetic component. Parents who have one child with autism may have a higher likelihood of having another child on the spectrum, a concept referred to as the recurrence rate.
In some cases, younger siblings of autistic children may not develop autism but could still exhibit traits associated with the condition or experience other developmental challenges, such as delays in language skills.
Families with multiple children often observe a spectrum of developmental variations, underscoring the complex nature of autism’s genetic and environmental influences.
Potential causes of autism during pregnancy
Certain conditions during pregnancy are considered non-genetic factors that may influence brain development and potentially contribute to autism.
Exposure to harmful substances, such as specific drugs or toxic chemicals during pregnancy, is thought to play a role in affecting brain development.
Premature birth, particularly in babies born before 35 weeks, has also been linked to a higher likelihood of developing autism later in life. Viral infections like rubella during pregnancy may increase the risk, too.
Pregnancy complications such as gestational diabetes, high blood pressure, abnormal bleeding, or delivering a low-birth-weight baby are associated with a higher likelihood of having a child with autism.
Despite ongoing advancements, there is currently no definitive test to determine whether a baby will develop autism.
Medications linked with autism during pregnancy
Pregnant mothers are often advised to be cautious with certain medications due to potential impacts on a child’s development.
Some medications, such as antidepressants, acetaminophen, and asthma treatments, have been suggested as possibly influencing the risk of autism.
While these connections remain a topic of ongoing investigation, some experts suggest that exposure to certain drugs during pregnancy, particularly in the first trimester, might affect brain development. However, further research is needed to fully understand these effects.
It’s essential for women to consult their healthcare providers before making any changes to their medications or health routines during pregnancy.
Autism and children born to older parents
Research suggests that parental age may influence the likelihood of having a child with autism. Older fathers, in particular, are believed to have a higher chance of passing on genetic mutations, which may increase the risk.
Similarly, the age of the mother also plays a role, with both very young and older maternal ages being associated with a greater likelihood of autism. Mothers over 40, for example, are thought to face an elevated risk compared to younger mothers.
Environmental factors associated with autism
It was previously mentioned that a single factor might not cause autism. Several studies support the theory that autism may also be the result of environmental factors.
Environmental factors are anything that is non-genetic. This includes:
- Taking certain drugs (thalidomide and valproic acid) during pregnancy
- Complications before, during, and after pregnancy
- Viral infections or metabolic imbalances
- Exposure to toxic chemicals
- Stress
Although there are studies that consider these factors as possible contributors to autism, they are not large enough to be deemed accurate.
Further studies are yet to be completed concerning how environmental conditions can cause or indirectly contribute to developing autism.
Biological causes of autism
People often ask what the biological causes of autism are. In addition to the genetic link to autism, scientists and researchers are taking a look at the neurobiological aspect and how it can also play a role in autism.
Different studies have collectively concluded that people with autism have brains that are physically different from non-autistic people.
Some of these differences are:
- Anatomical differences in the cerebellum and limbic system
- Bigger gray matter in frontal and temporal lobes
- Under-active amygdala when seeing facial expressions
- Because autism affects boys more than girls, researchers are looking at how prenatal testosterone levels might trigger autism in the womb.
To this day, studies and research are ongoing, and there is yet to be a definite answer as to what causes autism on a physical level. There is a reason to believe that biochemical causes of autism are possible, given these preliminary findings.
Do vaccines cause autism?
The CDC states that there is no link between vaccines and developing autism spectrum disorder.
The belief that vaccines cause autism started with a study in 1998 and another one in 2002 that concluded that certain vaccines for measles and rubella are linked with developing autism in children.
These studies have long been discredited, and the CDC has made it a point to educate parents and caregivers that vaccines are not what causes autism in babies.
What tests are used to diagnose autism?
A qualified doctor makes a diagnosis of autism. It has two parts:
- Developmental screening
- Diagnostic evaluation
In the developmental screening phase, the child is observed by a doctor and might be asked questions or given instructions. The doctor may even engage the child in play to see how the child speaks, listens, and acts.
What tests are used to diagnose autism? The doctor reviews all the information gathered before giving the diagnosis.
It may involve an interview with the parents or caregiver of the child. The doctor may also request further tests such as vision screening, genetic testing, and neurological testing to make a diagnosis.
Progress toward understanding the causes of autism
The question of what causes autism remains complex, with no single answer identified. However, ongoing efforts and advancements in understanding autism bring hope to families and caregivers.
Scientists and institutions around the world are working diligently to uncover the factors that contribute to autism. From genetic predispositions to environmental influences, each discovery helps to clarify the intricate puzzle of autism.
As progress continues, parents and caregivers gain valuable insights to better support their children and foster their development.
FAQs
Q: What is the cause of autism?
A: The exact cause of autism is unknown, but it is believed to result from a combination of genetic and environmental factors. Research suggests no single cause, but rather a complex interplay of influences during early brain development.
Q: Are you born with autism, or is it caused?
A: Autism is generally considered to be present from birth and linked to genetic factors. Environmental influences during pregnancy or early infancy may contribute but do not directly cause autism.
Q: At what age does autism start?
A: Autism typically begins to show signs in early childhood, often before the age of three. Developmental delays or differences may become noticeable as early as 12-18 months.
Q: Can autism develop later in life?
A: Autism does not develop later in life; it is present from birth. However, signs of autism may go unrecognized until adulthood, particularly in cases where symptoms are less pronounced.
References
Autism Spectrum Disorder. (12 February, 2019). Retrieved from https://ghr.nlm.nih.gov/condition/autism-spectrum-disorder#genes
Infantile Autism: A Genetic Study of 21 Twin Pairs. (September 1977). Retrieved from https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1469-7610.1977.tb00443.x
Sibling Recurrence and the Genetic Epidemiology of Autism. (1 October, 2010). Retrieved from https://iancommunity.org/cs/autism_spectrum_disorder_research/autistic_traits_in_siblings
16 Year Old ‘Vaccines Cause Autism’ Paper Withdrawn, Finally. (18 October, 2018). Retrieved from https://www.precisionvaccinations.com/mmr-vaccine-does-not-cause-autism-says-cdc
Autism risk factors: genes, environment, and gene-environment interactions. (September 2012). Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3513682/
Causes of Autism. Retrieved from https://www.asha.org/PRPSpecificTopic.aspx?folderid=8589935303§ion=Causes#Neurobiological_Factors
Premature babies and autism. (7 Apr 2008). Retrieved from https://www.nhs.uk/news/pregnancy-and-child/premature-babies-and-autism/#what-does-the-nhs-knowledge-service-make-of-this-study
Behavioral impact of maternal allergic-asthma in two genetically distinct mouse strains. (July 2017). Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/27622677/
Screening and Diagnosis of Autism Spectrum Disorder. Retrieved from https://www.cdc.gov/ncbddd/autism/screening.html
Latest research hints at predicting autism risk for pregnant mothers. (21 September, 2018). Retrieved from https://www.sciencedaily.com/releases/2018/09/180921151430.htm
Estimated autism risk and older reproductive age. (September 2009). Retrieve from https://www.ncbi.nlm.nih.gov/pubmed/19608957
