Biology and Causes of Autism

What is autism?

Autism is a neurodevelopmental condition that leads to certain differences in socialization and communication, as well as different behaviors. Autism is on a spectrum, so signs vary significantly in type and severity. The underlying biology of people with autism is not fully understood, and a single process in the brain has not been found.

What causes autism?

The consensus among scientists is that genetic factors cause changes in brain structure and neural connectivity, which affects socialization and communication skills and leads to characteristic behaviors in people with autism.

There is likely a strong genetic contribution to the development of autism. For instance, in a study of over 2 million families in Sweden, the overall risk of an autism diagnosis grew with familial proximity, suggesting genetics play a key role in the condition.

Since autism is both a spectrum condition and highly heritable, probably several genes or gene combinations are involved. Unfortunately, many aspects of the genetics of autism are not well understood by scientists, and research is ongoing to help us learn more.

The role of environmental factors in the development of autism is less clear. The Journal of the American Academy of Pediatrics describes the impact of environmental factors as “an area of active study that, as yet, is without firm conclusions.”

Vaccinations are not associated with the development of autism based on large-scale population data.

The number of children with autism spectrum disorder (i.e., prevalence) in the United States has risen significantly over the last 20 years—from approximately 1 in 150 US children in 2000 to 1 in 54 US children (or 1.85% of US children).

This increase is likely due to broader diagnostic criteria, which means more children meet them, as well as increasing awareness of and screening for autism. It is also possible that there has been a true increase in the underlying autism prevalence.

What are the signs and symptoms of autism?

The initial signs of autism can vary significantly for each child. Different children will often show different signs—with some showing many signs and others demonstrating only a few.

The time course is also unique to each person, with some children showing signs at a very young age (first few months of life), others showing signs after 1-2 years, and still others appearing to regress in later childhood and lose abilities they used to have (e.g., losing communication skills). Some people demonstrate certain symptoms of autism but don’t have autism spectrum disorder.

Because of this complexity, a specialized health care provider is needed to establish a diagnosis of autism. Typically, an evaluation is done by a medical provider such as a developmental behavior pediatrician, child psychiatrist, or pediatric neurologist or by a licensed clinical psychologist.

If you notice signs in your child and are concerned about their development, talk to your pediatrician about a formalized assessment. Be open with your pediatrician about these concerns so that any potential challenges can be caught early.

The signs of autism span 2 domains: 1) differences in social communication and social interaction, and 2) restricted and repetitive patterns of behavior.

It is worth repeating—a specialized health care provider is required to make the diagnosis of autism, and

if you are concerned that your child may have autism or another developmental delay, talk to your

pediatrician or another specialist. We also offer this service at Soar.

What are common strengths of children with autism?

Children with autism often have unique strengths relative to their neurotypical peers. One research article pinpointed strengths across 5 themes of Personality Characteristics, Social Personality, Cognitive Functioning, Behavioral Characteristics/Coping Mechanisms, and Skills.

Some children may develop “savant” skills in specific areas that interest them, such as memorization and recall of facts, numbers, or trivia. Autism Speaks also identified the following 7 areas of skill among people with autism:

  • Sharp memory
  • Intense focus on the task at hand
  • Skills in STEM (science, technology, engineering, and mathematics) fields
  • Honesty
  • Adherence to rules and directives
  • Talents in music (e.g., playing music from memory) and art (e.g., drawing or painting)
  • Hyperlexia (reading at an early age)
Common Situations Parents of Children With Autism May Face
The Signs of Autism


  1. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders (DSM-5), 5th ed. Washington, DC: American Psychiatric Association; 2013
  2. Hyman et al. Identification, Evaluation, and Management of Children With Autism Spectrum Disorder. Pediatrics (2020), doi: 10.1542/peds.2019-3447
  3. Sandin et al. The familial risk of autism. JAMA (2014), doi: 10.1001/jama.2014.4144
  4. Taylor et al. Vaccines are not associated with autism: an evidence-based meta-analysis of case-control and cohort studies. Vaccine (2014), doi: 10.1016/j.vaccine.2014.04.085
  5. Centers for Disease Control and Prevention. Data and Statistics on Autism Spectrum Disorder.
  6. Centers for Disease Control and Prevention. Signs and Symptoms of Autism Spectrum Disorders.
  7. Sabapathy et al. Parent-Reported Strengths in Children with Autism Spectrum Disorders at the Time of an Interdisciplinary Diagnostic Evaluation. J Dev Behav Pediatr (2017), doi: 10.1097/DBP.0000000000000423
  8. Autism Speaks. 100 Day Kit For Families of Newly Diagnosed Young Children.

Soar Autism Center

Reach out today