Is Autism Genetic? Understanding the Causes of Autism Spectrum Disorders

Autism spectrum disorder (ASD) is a complex condition affecting an estimated 1 in 68 children in the United States alone. The condition often presents with communication difficulties and social impairments, and effects can range from mild to severe. Ranging from speech delays to repetitive behaviors, the symptoms of autism can vary in severity and complexity.

While much is still unknown about autism, one consistent fact remains: autism is almost certainly caused by a combination of genetic and environmental factors. Here, we’ll explore the ways in which genetics affects autism and what science says about the condition’s genetical predisposition.

What is Autism Spectrum Disorder?

Autism spectrum disorder (ASD) is the umbrella term for a group of complex, long-term developmental disorders that are typically diagnosed in early childhood development. People with ASD may have difficulties with communicating and interacting in social situations, and may have restrictive or repetitive interests, behaviors and activities. Symptoms may range from mild to severe. Research suggests that ASD is a biological disorder with many genetic, environmental and other contributory factors.

The Impact Of Genetics On Autism

Family studies have long suggested that genetic factors play an important role in causing autism. Through examination of families with more than one affected child, it has been determined that ASD is very likely to have genetic involvement – more than just a single gene.

In the U.S. alone, over 10 years of research has been conducted on autism and genetic factors, suggesting complex and multiple causes in each individual. There can be any number of contributing genetic or environmental factors that could influence the disorder’s onset, and in various proportions. It has been estimated that 80% to 90% of autism cases are the result of genetic and environmental factors – together.

Structure Of The Human Genome

The human genome is the complete set of instructions that determines the entirety of the human form, from hair color to personality. It is composed of three billion nucleotides – the building blocks of genetic sequences – comprising roughly 25,000 genes. Each set of instructions is tied to a specific trait, and one’s overall genetic composition is determined by mutations, copy errors and other random chance events.

It is these random events and small changes in genetics that can lead to the development of autism in some children. Therefore, while there is no “autism gene,” it is the small genetic changes that accumulate that can have the most significant effect on the overall development of a child, resulting in a disruption of normal brain development.

Common Genetic Variants Linked To Autism

While it remains unclear exactly what causes autism, researchers have discovered several genetic variations that are associated with increased risk for developing the disorder.

Researchers have identified several common genetic variants that appear to increase the risk for autism, including, but not limited to:

• Copy number variations (CNVs): CNVs are changes in genetic sequences that are common in people with autism, affecting several genes and possibly impacting brain development.

• Mutations in “high-risk” genes: “High-risk” genes are those that have been associated with a higher risk of autism, when a mutation occurs. These can include genes such as: CHD8, SHANK3, and SCN2A.

• Maternal or paternal inheritance of genetic variants: This refers to the passing on of genetic variants from one generation to the next, which may increase the risk of autism in some individuals.

What Science Says About Genetical Risk Of Autism

Although there is no one single gene that causes autism, researchers have drawn correlations between certain genes and an increased risk of autism.

Studies have indicated that a variety of influences, including inherited genetic susceptibility, are likely involved in autism and various other characteristics of the condition.

Research has also indicated that inherited environmental conditions, such as the exposure of pregnant women to environmental toxins or stress, can also increase a child’s risk of developing autism.

Diagnosing Autism: Genetic Testing

When diagnosing autism, a thorough assessment of the individual’s medical, psychiatric, behavioral and developmental history is used to determine a diagnosis. Genetic testing may also be used to identify any potential genetic variants that could be associated with autism and other factors.

The most common genetic tests used include:

• Chromosomal microarray analysis: This looks for any missing or extra genetic material in a person’s chromosomes.

• Whole Exome Sequencing: This looks at the entire code of a person’s genetic material, examining all of the exons – the coding regions of a gene – for any abnormalities or mutations.

• Fragile X testing: This test looks for a mutation in a gene called fragile X, which is associated with an increased risk for autism.

From family studies to genetic testing, it is becoming clear that autism is an incredibly complex disorder, with multiple contributing factors at play. Science points to genetic and environmental influences as the primary causes of autism, and while it is still unknown exactly what causes the disorder, research is continuing to uncover more of the mystery behind autism.

Overall, while the exact causes of autism remain unknown, the central role of genetics in the condition is well-documented. A comprehensive understanding of the medical, developmental and family histories of the individual remains the most important step when diagnosing autism, and genetic testing may also be used to identify any genetic variations that could be associated with the condition.

No one knows exactly why autism affects some people and not others, but research continues to uncover more of the mystery and work towards a better understanding.