Medically Reviewed By Sonam Kothari, Written By Tejasvi Parekh
Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by symptoms such as problems in social interaction, difficulty in communication, and repetitive behaviours.
The increasing prevalence of ASD globally has compelled researchers to find the factors underlying the disorder. One of the important lines of investigation is the role of genetics in ASD.
Genetic factors are considered to be critical in the development of ASD. While genetic contributions are believed to be one of the major risk factors that influence the likelihood of its occurrence in people, the sole cause of ASD cannot be attributed to genetics.
Specific genetic mutations and variations identified have further enhanced the understanding of the disorder.
This article aims to shed light on how genetic predispositions contribute to ASD and the potential for advancing our understanding of this disorder.
According to Daniel H. Geschwind, one of the most influential researchers in ASD, ASD is an aggregation of causal factors. In the same way, pneumonia could be caused by many different things, such as bacteria, viruses, or fungi, ASD can have many causes.
There are between 200 to 1,000 genes that might make someone more likely to have ASD. On the other hand, cases of ASD caused by things like certain chemicals during pregnancy are much less common.
Genetics are a significant contributor to autism spectrum disorder (ASD), accounting for approximately 40% to 80% of the risk. Research indicates that ASD tends to run in families. For instance, if one child is diagnosed with ASD, there’s a higher probability that siblings may also be affected or show symptoms of ASD.
Studies involving twins have highlighted this genetic influence. Monozygotic (identical) twins, who share 100% of their genes, are more likely to both have ASD compared to dizygotic (fraternal) twins, who share about 50% of their genes
In a study utilizing a twin design to investigate the causes of autism spectrum disorders (ASDs) and autistic traits over time, Taylor and colleagues discovered that genetic factors consistently had a more significant impact compared to environmental factors.
Their findings suggest that environmental factors alone are unlikely to account for the rising prevalence of ASD.
Genetic research has shown that a wide array of genes are involved in ASD, contributing to its complex nature. These genes often affect brain development and function. For example, some genetic variations can disrupt neuronal communication and the formation of neural networks, leading to difficulties in social interaction and communication.
Autism spectrum disorder (ASD) has complex genetic origins. While many genes contribute to ASD risk, only a few rare forms are linked to changes in a single gene, such as in Rett syndrome and Fragile X syndrome.
Most cases of ASD involve a combination of genetic factors. Some of these are inherited from parents, while others are new genetic changes that occur randomly during the formation of egg or sperm cells. These random changes are called "spontaneous mutations."
Since the early 2000s, advances in genetic analysis technology have significantly improved our understanding of ASD's genetic basis. Researchers can now examine genetic information more quickly and thoroughly than ever before
This technology revealed that ASD involves many small genetic variations rather than a few common mutations.
Interestingly, recent studies suggest that ASD-related genes may be more commonly inherited from the father, challenging earlier beliefs that maternal genes were primarily responsible.
Family history is a crucial factor in understanding the inherited risk of ASD. Research consistently shows that having a family member with ASD increases an individual's likelihood of developing the condition. While a family history of ASD does not guarantee that a child will also have ASD, it significantly raises the risk.
Studies examining the recurrence risk of ASD in families reveal that the likelihood of ASD is notably higher in siblings of individuals with ASD than in the general population. For example, if one child in a family is diagnosed with ASD, siblings are at a much higher risk compared to children without an affected sibling.
This pattern also extends to twins, where identical (monozygotic) twins have a higher concordance rate for ASD compared to fraternal (dizygotic) twins.
The table below illustrates the estimated recurrence risks of ASD based on family relationships:
|
Family Relationship |
Recurrence Risk |
|
Sibling |
10-20% |
|
Fraternal Twin |
3-7% |
|
Identical Twin |
30-40% |
These numbers reflect that the risk of ASD increases with closer family relationships.
While family history and genetic factors are significant, they are not the only contributors to ASD Other genetic variations and environmental factors also play a role in the development of ASD.
Factors such as prenatal exposure to certain substances, complications during pregnancy, and early childhood experiences can interact with genetic predispositions.
A recent groundbreaking study by UCLA Health researchers has provided new insights into ASD genetics by examining families with multiple children diagnosed with the disorder. This study, the largest of its kind, identified seven new potential risk genes linked to ASD.
The research helps explain why some parents who carry rare mutations might not show signs of ASD themselves, yet their children do.
Besides, the study showed a significant association between language delay with ASD risk. This means that children who showed a delayed language ability were more likely to possess a genotype associated with ASD, indicating that the language delay could be a core feature of ASD.
The results bring into question the validity of the current diagnostic criteria since language delay is not considered a core symptom for ASD diagnosis.
Overall, the study underscores the importance of including families with multiple affected children in genetic research and suggests that language delay should be reconsidered in the context of ASD diagnosis.
Yes, a majority (around 80%) of Autism Spectrum Disorder (ASD) cases are hereditary, with most cases linked to inherited genetic mutations passed down through families.
No, ASD starts during fetal development, and there is no evidence that it can develop later in life. There is no evidence that children can develop ASD later in life due to exposure to vaccines or postnatal toxins.
Currently, there is no known cure for Autism Spectrum Disorder (ASD). ASD is a lifelong neurodevelopmental condition, and the focus of treatment is on managing symptoms and improving quality of life rather than curing the disorder.
