Do we know what causes autism? Let’s look at the science

by Shea Brogren, MOT, OTR/L January 16, 2020

Do we know what causes autism? Let's look at the science!

As of 2018, the CDC estimates that approximately 1 in 59 children has a diagnosis of autism spectrum disorder (ASD). This statistic can be broken down further to 1 in 37 boys and 1 in 151 girls.

The prevalence of ASD continues to increase, yet the direct cause of autism is still unknown. There are several risk factors for developing ASD, however, research has not been able to pinpoint a definitive cause, making this disorder and the increasing prevalence more alarming.

In this article, we will briefly review the symptoms of autism and break down the potential causes and established risk factors. 

What are the characteristics of autism? 

Autism can be a perplexing disorder, as each child diagnosed will have their own unique presentation of symptoms. Some children will have very mild symptoms, while others are profoundly affected. Generally speaking, below are characteristics associated with autism spectrum disorder:

Difficulty with communication and social interaction:

  • Difficulty maintaining appropriate eye contact
  • Not able to understand non-verbal cues, others’ expressions, or emotions of others
  • Difficulty starting a conversation and continuing a conversation
  • Has delayed speech
  • May repeat certain phrases or words, but unable to use them in everyday language
  • Difficulty expressing emotions

Cognitive difficulties: 

  • Poor planning skills 
  • Trouble with organization 
  • Difficulty with problem-solving 
  • Inhibition problems or difficulty with self-monitoring thoughts 

Behavioral, motor, and sensory concerns:

  • Engaging in repetitive movements, such as hand flapping or rocking back and forth 
  • Has developed specific routines and rituals 
  • Becomes dysregulated when routines and rituals are not followed 
  • Becomes fixated on certain objects or certain parts of objects 
  • Has food preferences and aversions, for example being bothered by certain food textures
  • Has specific sensory sensitivities, which might include light, noises, certain clothing fabrics or textures    
  • May engage in rough play and not realize roughness of actions/movements 
  • May have difficulty with coordination and engaging in physical activity  

Again, it is important to note that each child will have their own unique symptom presentation. Your child’s pediatrician can help with assessing symptoms and referring to potentially needed services. 

What are the possible causes of autism?        

There have been numerous research studies conducted investigating the causes of autism, however, the conclusion is that there is no one definite cause of autism spectrum disorder. The consensus is that autism is likely caused by a combination of genetic and environmental factors. Below, we will outline the potential environmental and genetic factors. 

Genetic factors related to autism

Genetic factors and autism

Genes are passed down from parents to their children during prenatal development. In some instances, genes experience mutations during development. This means that they don’t develop in the same way as healthy, functional genes and this can lead to developmental issues, including autism spectrum disorder.

For example, a certain gene may mutate and have an effect on brain development or have an impact on how cells communicate in the body. The majority of autism research has concluded that genes play at least some role in a child developing autism. However, there have been several genes identified that could potentially cause autism symptoms and because of this, no direct gene can be named at this time. 

Environmental factors related to autism

We can conclude that genetics play at least some role in autism, so what other factors might be involved?

Researchers have suggested a variety of potential causes related to environmental factors. When we use the term “environmental,” we are referring to any other potential cause besides a person’s genetics. Some of the suggested causes include a viral infection, air pollutants, pregnancy complications, and exposure to certain chemical toxins.

There are rigorous research studies being conducted on each of these areas to better determine how they might be linked to causing autism. The current conclusion is that a combination of genetics and environmental factors cause autism.

Are there risk factors for autism? 

Though a direct cause of autism cannot currently be identified, there are several characteristics that have been identified by researchers as “risk factors” for developing autism. This means that if a child possesses any of these characteristics, they may be more likely to develop autism when compared to a child who does not possess the characteristic.

Below are some of the identified potential risk factors for autism. 


Autism is more commonly found in boys, as they are four times more likely than girls to develop autism. 

Family history

Research has shown that autism tends to run in families. If there is one child in the family with autism, the risk increases for having another with autism. In addition, twin studies have shown that if one twin has autism, then the other twin (identical) has a 76% chance of also being diagnosed. These statistics are most of the foundation for the conclusion that autism has a genetic component. 

Preterm birth

If a child is born before 26 weeks gestation, they have a greater likelihood of later being diagnosed with autism. 

Parental age

Some studies suggest advanced parental age (over 35 years) can put a child at a greater risk for autism. 

Other medical diagnoses

There are several other medical diagnoses that have also been associated with autism-like symptoms. Some of these diagnoses include Rett Syndrome, Fragile X Syndrome, and Intellectual Disability. 

Please note that these are just potential risk factors and this list is in no way meant to diagnose or evoke worry for parents. The causes and risk factors of autism have been studied greatly over the past several years, however, there still is no direct cause that can be identified.

The risk factors described above help us understand a child’s potential for developing autism but they are not a direct cause of autism. 


Though research on potential autism causes and the most effective treatment options has increased over the past decade, no definitive cause can be identified at this time. It is important to recognize, however, that advances in research have helped us better understand autism and we can now say that there are both genetic and environmental links to autism.

This information can help researchers further narrow down their areas of study to hone in even more on the potential causes. Overall, even if one cause has not been identified, the public is becoming more aware of autism symptoms and potential causes.

This awareness is crucial as it has allowed more children to receive services at an earlier age, which is the best way to ensure positive outcomes for children with autism and their families. We hope this article provided clarity on potential autism causes and highlighted the need for continuing research! 


Amaral, D.G. (2017). Examining the causes of autism. Cerebrum, 17

Chaste, P., & Leboyer, M. (2012). Autism risk factors: Genes, environment, and gene-environment interactions. Dialogues in clinical neuroscience, 14(3). 

Shea Brogren, MOT, OTR/L
Shea Brogren, MOT, OTR/L

Shea Brogren, MOT, OTR/L, is an occupational therapist with over three years of experience in pediatrics and child/adolescent mental health and has also worked as an adjunct lecturer at the University of North Dakota. Shea has a special interest in program development and developed and implemented occupational therapy programming at a residential treatment center for children. She now practices in an outpatient setting.

Her primary area of interest involves working with children who have experienced developmental trauma. Shea has advanced training in SMART treatment (Sensorimotor Arousal Regulation Treatment), the Zones of Regulation, using sensory-based interventions to address trauma, infant mental health, attachment, and arousal regulation related to trauma disorders.

Leave a comment

Comments will be approved before showing up.

Also in Special Needs

Autism & Jobs Blog Post
The Ultimate Guide to Employment for People with Autism

by Molly Shaw Wilson MS OTR/L BCP October 16, 2020

It's so important for individuals with autism to be prepared for the adult world so that they can lead more meaningful lives beyond their school years. Follow our awesome guide filled with resources and steps you can take toward the optimal career path!
Read More
Anger & Autism Blog Post
Our Best Strategies for Dealing with Autism and Anger

by Shea Brogren, MOT, OTR/L October 05, 2020

Anger is often an emotion that is associated with autism spectrum disorder. Most children with autism do not express anger in the same way as typically-developing peers. This article will explain why this happens and provides recommendations to help.
Read More
Autism & Food: How to Deal with a Picky Eater
Autism and Food: How to Deal with a Picky Eater

by Jennifer Friedman, MS, RD August 12, 2020

Did you know that 50 to 75% of children with autism have food issues? If you're dealing with this at home, you are not alone! Read our article to know how to distinguish severe or extreme picky eating from traditional picky eating behaviors and what steps you should take to help.
Read More