What role does the environment play in autism?

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Autism, also known as autism spectrum disorder (ASD), is a range of conditions that affect a person’s communication and behavior. Autism usually appears by 2 years old.

Individuals with autism may encounter difficulties in social interactions, engage in repetitive behaviors, and experience challenges in academic and professional settings.

Learn more about autism.

Certain factors can occur in the environment of a pregnant person and baby that may contribute to the development of autism.

Research divides environmental factors into three categories:

• prenatal (before birth)
• natal (during birth)
• postnatal (after birth)

According to the National Institute of Environmental Health Sciences, these factors can include:

• older parental age
• exposure to air pollution or certain pesticides before birth
• conditions affecting the pregnant person, such as:
  • obesity
  • diabetes
  • immune system disorders
• premature birth or low birth weight
• any birth difficulties, such as periods of oxygen deprivation to the baby’s brain

However, these factors alone are unlikely to cause autism. Genetic factors are also involved.

Research from 2017 looked into these three categories of environmental factors of ASD and found the following:

Prenatal environmental factors

• physical health of the pregnant person, such as the presence of metabolic syndrome or viral infections in the first trimester
• mental health issues in the pregnant person, such as depression and anxiety, particularly during weeks 21 to 32 of pregnancy
• parental age, especially paternal age, above 34 years
• certain prenatal medications, such as antiepileptic drugs and antidepressant medications
• lower socioeconomic status

Natal environmental factors

• fetal complications, which may lead to a lack of oxygen
• umbilical cord complications
• bleeding during pregnancy
• premature or late birth

Postnatal environmental factors

• jaundice
• postnatal infection
• vitamin deficiencies
• low levels of care
• chemical exposure

Some people have anecdotally suggested that vaccines may be linked to autism, but no evidence supports this.

Research has found no association between measles or measles, mumps, and rubella (MMR) vaccines with ASD.

Evidence also rejects that bad parenting causes autism.

While scientists suggest that diet during pregnancy is important for a child’s neurodevelopment, that is not to say that an unhealthy diet directly causes autism.

Genetics and environmental factors play a primary role in determining autism.

There are specific genetic and environmental factors that may increase the chance of ASD, including:

• a mutation in a gene called MET combined with high levels of air pollution
• gestational diabetes or obesity
• fever during pregnancy

Research suggests other factors that increase the chance of autism include:

• parental age, especially paternal age, older than or equal to 34 years
• parental psychiatric history, such as depression or schizophrenia

There is not just one cause of ASD. A variety of factors play a role in contributing to it.

The Centers for Disease Control and Prevention (CDC) suggests that while there is still more to understand in terms of specific causes, evidence suggests having a sibling with ASD or certain genetic conditions, such as fragile X syndrome or tuberous sclerosis, may pose a greater chance of autism.

A 2019 study that examined population data from five countries estimates that the heritability of autism is approximately 80%.

A 2023 research review found that the longer and earlier a child has screen exposure, the higher the chance they may develop ASD. Screens may be a critical issue for a child’s neurodevelopment and communication.

Read more about the causes of autism.

The CDC suggests ASD can place a great deal of stress on the autistic child as well as their family.

Families can seek support for managing any difficult situations, particularly during transitions, such as through school and beyond. Changes in routines may particularly cause a great deal of anxiety.

According to the United Kingdom’s National Health Service, other areas that an autistic child may need support with include:

• managing feelings and identifying them
• eating issues, such as only wanting to eat certain types of food or problems with coughing and choking
• sleeping problems caused by anxiety and sensitivity to light
• maintaining friendships and socializing

Parents and caregivers can support an autistic child by:

• learning how and when to offer support
• understanding triggers
• accepting the child’s differences and celebrating their strengths
• celebrating small wins and learnings
• being consistent and patient
• creating routines and following them where possible
• teaching behavior through rewards and consequences, referred to as applied behavior analysis
• creating a safe space at home
• understanding nonverbal cues to support communication
• encouraging activities they enjoy
• avoiding overstimulating environments where possible or introducing them gradually

People can visit the Autistic Self Advocacy Network for more support and resources.

Environmental factors may occur before, during, or after pregnancy that can affect the chance of developing autism.

Prenatal factors may include parental, especially paternal, age above 34 years and maternal mental and physical conditions.

Factors that may occur during birth include possible fetal complications or early or late birth. Postnatal factors may include chemical exposure or vitamin deficiencies.

Research has not found evidence that a bad diet, vaccines, or parenting styles influence autism.

There is not just one cause of ASD. Genetics and environmental factors both play a role.

Resources are available for parents and caregivers of an autistic child. If they have any questions or need help accessing support, they can reach out to their pediatrician for advice.