Asperger’s syndrome isn’t currently used as a diagnosis, so much of what causes autism spectrum disorder likely also plays a role in causing Asperger’s.

Asperger’s syndrome is a neurodevelopmental condition that involves social communication and behavior.

In 2013, Asperger’s syndrome — which used to be considered a separate condition — was reclassified as a subtype of autism spectrum disorder (ASD).

Today, doctors often diagnose what used to be called Asperger’s as autism. Some people also call it “high-functioning” autism.

The Centers for Disease Control and Prevention (CDC) estimates that 1 in 54 children are autistic, but the numbers for Asperger’s vary widely. Boys are more than four times as likely to have an autism diagnosis as girls.

Some theories about the cause of Asperger’s symptoms now have significant evidence. The genetic and environmental bases for autism are becoming clearer and clearer, but researchers continue to search for more specific answers.

A quick note

Many autistic people (and people who advocate for them) don’t see autism as a disability or as something that needs treatment. Instead, it’s a part of who they are.

Research into the causes of autism is often tied to prevention. Some autistic people propose that less emphasis should be placed on the causes of autism and more should be placed on supporting autistic people.

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Autism spectrum disorder is marked by patterns of personal, social, or academic functioning and repetitive behavior. Features of autism are usually present in early childhood. They can affect daily activities in different ways.

Features of Asperger’s tend to mean that the person has fewer support requirements than autistic people who may require higher levels of day-to-day support.

People who meet the criteria for Asperger’s still display patterns of social skills and behavior, but their cognitive development and language abilities tend to fall into the average range according to neurotypical standards.

Many people with Asperger’s, their family members, and mental health researchers still consider Asperger’s to be different from autism.

In addition to possible biological differences, some “Aspies” feel the removal of Asperger’s syndrome as its own diagnosis is a threat to their identity and could limit their access to services.

Some features of Asperger’s syndrome include:

  • communication differences
  • clashes in social interaction (especially in nonautistic settings)
  • repetitive behaviors (sometimes called “stimming”)
  • eye contact avoidance
  • preference for set routines
  • irritability
  • anxiety

Many autistic people and mental health workers don’t view autism as a disability or disorder, but rather a variation in human thinking that should be celebrated.

But currently, the standard scientific terminology for describing autism still includes these words.

There’s no single known cause of Asperger’s or autism spectrum disorder. Scientists believe that an interaction of many factors, including genetics and environment, contributes to these conditions.

Genetic causes of Asperger’s syndrome

The role of genetics in causing autism is one of the most prominent and well-researched theories.

Research has identified mutations in many genes, some that control brain development and brain cell communication, that could be associated with autism spectrum disorder.

Many studies have shown that autism is hereditary, though estimates for exact rates vary widely. Having an autistic sibling is connected to a 10- to 153-fold increase in the chances of receiving an autism diagnosis.

Asperger’s, or “high-functioning” autism, is likely even more familial than autism at other points along the spectrum.

Family members of people with Asperger’s are also more likely to show behavioral symptoms similar to those seen in autism even if they haven’t received a diagnosis.

Genetic disorders that affect single genes, like fragile X syndrome (FXS) and tuberous sclerosis, can also contribute to autism. In one study, around 20% of females and half of males with FXS also met the criteria for autism.

In the remaining cases of autism, the underlying cause seems to be “polygenic,” or brought on by differences in many genes. The way autism presents is likely determined by a specific combination of relevant gene versions.

Genes may also help explain why there are more autistic males than females: Some experts believe that having two X chromosomes reduces a person’s chances of being autistic. This is partly because more genetic mutations are needed in females to produce autism.

Scientists are also focusing more and more on the role of epigenetics, or the influence of environmental factors on gene expression, in Asperger’s and autism.

Environmental causes of Asperger’s syndrome

There’s growing evidence for the role of environmental factors in the development of Asperger’s and autism, but more research is certainly needed.

Some medical conditions in pregnant parents have been shown to increase the likelihood of the child developing autism. These include:

Taking antidepressants while pregnant may be associated with Asperger’s specifically. But studies indicate that if they do have an impact, it’s likely very small.

Some studies suggest that people exposed to certain chemicals during the early stages of pregnancy are more likely to have autistic children. Potentially harmful chemicals include:

Premature birth and complications during pregnancy and labor may also increase the chances of autism in children. Injury to parts of the brain and susceptibility to environmental stressors is higher for preterm babies.

It’s still unclear how important or impactful many of these environmental factors are in causing Asperger’s or autism. If you’re concerned about any of these factors, talking with a healthcare professional might be a good idea.

Overall, many environmental factors have been connected to autism. While some research has been done, much more is needed before they can be considered causes. Some of these include:

Biology and brain differences in Asperger’s syndrome

Along with genetics and environmental influences, biological factors and brain differences are often linked to autism.

Brain abnormalities in the following areas have been found in autistic children:

  • cerebellum
  • prefrontal and temporal cortexes
  • hippocampus
  • amygdala

Research suggests that neurons in the brains of autistic people are often either under- or overconnected.

Differences in the concentration of some neurotransmitters, responsible for supporting communication of signals in the brain, have also been found in people with Asperger’s syndrome.

Researchers have suggested and continue to investigate many other factors that may increase the chances of having Asperger’s, even if they’re not direct causes.

Parental age

The age of the parents has been shown to be one of the most impactful environmental factors in the development of autism.

Parents in their mid-to-late 30s and above at the time of conception are more likely to have autistic children.


As mentioned, boys are four times more likely to receive an autism diagnosis than girls.

In addition to theories about the effects of XX versus XY chromosomes, research also suggests that underdiagnosis in girls could be a key reason why.

Birth type

Some studies have found increased rates of autism in children born via cesarean delivery.

It’s theorized that the lack of exposure to certain bacteria or the toxicity of general anesthesia are underlying reasons for this association, but more research is needed.

Birth order

Evidence indicates that the first child is significantly more likely to be autistic than the children born after them.

It’s crucial to note that many previously suggested causes of autism have been thoroughly debunked.

Some factors once wrongly thought to contribute to Asperger’s and autism include:


Despite common disinformation, extensive and detailed research has shown time and time again that vaccines do not cause autism.

Vaccines are widely regarded as safe and beneficial to the health of children and the public at large.

Parenting practices

A theory claiming that lack of affection from so-called “refrigerator mothers” leads to autism has long been discredited. Autism originates very early on in development. Parenting styles or neglect don’t cause it.

Diet or nutrition

Though it’s possible that dietary changes may help soothe some physical symptoms associated with autism, there’s no evidence that diet or malnutrition can cause autism.

As discussed earlier, the new classifications of mental health disorders mean that many people previously diagnosed with Asperger’s syndrome would now receive an autism spectrum disorder diagnosis.

Along with social communication patterns, an autism diagnosis means repetitive patterns of behavior or interests.

Unlike other presentations of autism, people with Asperger’s don’t have delayed language or cognitive development. This can be harder to identify and requires a good understanding of a child’s needs and development.

Children may be screened periodically for developmental signs linked to autism from a:

  • psychologist
  • neurologist
  • psychiatrist
  • other professional knowledgeable about diagnosing autism

For autistic people who need different levels of support, there are many resources available. These include:

  • therapy
  • medication
  • occupational therapy
  • social skills training

There’s no single cause of Asperger’s syndrome. Genetics, environment, and interactions between them play a role in its development.

Research is ongoing and far from complete, but we have a better sense than ever before of what factors contribute to autism.

If you believe you or someone close to you could have Asperger’s, or for more information about managing the symptoms, you can check out the resources below: