A young girl playing alone with colored clayAutism, or ASD, affects about 1% of people worldwide. Its diagnosis can be contentious. This is partly because autism diagnoses have recently increased. Some of the criteria for ASD are still widely debated. 

Autism affects the nervous system. One sign of autism is impaired social behavior. Other signs include restricted or repetitive behavior.

People once saw intensive support as the main way to manage autism. But current treatments often take a different approach. These treatments have improved social behavior in people with autism. When started in childhood, they may have higher chances of success.

The Diagnostic and Statistical Manual (4th ed.) listed Asperger’s syndrome (AS) as a disorder. AS is not listed by name in the DSM-5. The DSM-5 describes AS as social communication disorder. It is considered to be on the autism spectrum. Criteria for autism now use similar terms to describe Asperger’s. However, some people still refer to their condition as Asperger's.

What Causes Autism?

Find a Therapist

Advanced Search
The causes of autism are unknown. Some speculate that outside factors play a role. These factors could trigger a genetic propensity for autism. Family and twin studies show some people are more likely to have autism. This is due to their genes. Research has not yet discovered the genetic factors that cause ASD. 

Brain scans show some differences in the brain shapes of children with autism. This may mean a difference in brain structure or function causes the condition. Some other genetic conditions are linked to autism. Some of these conditions include:

  • Fragile x syndrome
  • Tuberous sclerosis
  • Untreated phenylketonuria (PKU)
  • Congenital rubella syndrome

Research has not yet found what is causing the increase in autism cases. Non-genetic factors may affect how autism develops. These factors may trigger autism in at-risk people, not cause it. Researchers are still exploring possible causes of autism.

Do Vaccines Cause Autism?

Some groups say chemicals in vaccines cause autism. But research shows no links between vaccines and autism. This theory is still popular among some. One reason for this is the rising number of diagnoses in recent years. The increase in diagnoses may be due to more research on autism. New research has led to a wider definition of ASD. An increase in cases could have occurred as a result.

Autism Signs and Symptoms

The DSM-5 lists autism as a social (pragmatic) communication disorder. Diagnosis often occurs when symptoms show in childhood. These symptoms must not be better explained by another condition. Some symptoms of autism include:

  • Difficulty following social norms like taking turns or listening
  • Avoidance of social groups or relationships
  • Restricted behaviors
  • Repetitive behaviors, called “stimming”
  • Tendency to stick to routines
  • Dislike of changes in routine
  • Over or under-responsive to sensory input

Some experts think using words functionally rules out autism. Others diagnose autism more readily despite what the DSM-5 recommends. 

Other conditions are also on the autism spectrum. Asperger's is one of the most notable of these.

Asperger's Syndrome

Asperger's was once known as “high-functioning autism.” Its symptoms are often similar to but less severe than autism. Delays in language and speech may not be present in Asperger's. People with Asperger’s may live without a diagnosis for years. This is because their behavior can appear "normal," if socially awkward.

Asperger's is now part of the autism spectrum. But there are some common signs of the condition. These behaviors and symptoms will impact daily life. They will appear in early childhood. Symptoms of Asperger’s may include:

  • Normal language development and intelligence
  • Desire to fit in and relate to others but uncertainty over how to do so
  • Social awkwardness
  • Difficulty expressing emotions and empathy
  • Avoiding eye contact
  • Confusion with social cues like body language or sarcasm
  • Strong interest in a narrow set of topics
  • Clumsiness or motor skill delays

A boy lying on a sofa uses a handheld deviceOne in 68 children may receive an ASD diagnosis in the United States. Of these, up to 75% may be Asperger’s or a related condition. This means as many as 2.6 million people in the U.S. may live with Asperger’s or a related condition. About 12% of people with ASD have full-time jobs.

Co-occurring Issues and Related Conditions

Some health issues can co-occur with autism. People may also develop mental health issues as a result of the condition. ASD can make people feel lonely, isolated, or anxious. The following issues are related to ASD:

  • Health/medical issues. Autism has many co-occurring medical conditions. Studies found families with an autistic child spent $4,110 to $6,200 more per year on medical bills.
  • Tourette syndrome. This condition affects nearly 1 out of 160 children. It occurs more often in boys. People with Tourette syndrome often display tics. These are involuntary vocal or physical behaviors.
  • Rett syndrome. This genetic condition slows development. It can cause repetitive behavior. It affects mostly girls. Rett syndrome differs from autism in key ways. Children with Rett often show a preference for people over objects.
  • Pica. About 30% of children with autism have pica. Pica causes people to crave inedible objects. These can include dirt, ice, or paper.
  • Sleep issues. Up to 80% of children with autism have sleep issues. These issues may include insomnia. Certain brain differences are tied to autism. Research suggests these may affect sleep.
  • Sensory processing issues. This is called Sensory Processing Disorder (SPD) in the DSM-5. It often occurs in people with autism. It causes over- or under-sensitivity to sensory input.
  • Seizures. People with autism may be prone to seizures. Statistics show epilepsy occurs in about 30% of people with autism.

Autism in Men and Women

Men are more likely to receive an ASD diagnosis. The ratio of men to women diagnosed ranges from 2:1 to 16:1. This difference has existed since autism was first studied. Males may be more likely to inherit disease linked to autism. Research on autism may center more often on men and their experiences.

Studies show symptoms do not tend to differ between men and women. But women may cope with their symptoms differently. This could affect the rates of ASD diagnoses in women. These coping skills may also mask unusual behavior from others. Researchers call this “camouflaging.” Social or coping skills can make it easier for women to hide social discomfort. 

Women may mask autism with displays of emotion. They might act out behavior considered to be “normal.” But camouflaging may not be healthy long-term. It can lead to stress or depression in women with ASD. It may also cost them a diagnosis.

History of Autism

Psychiatrist Eugen Bleuler first used the term autism in 1908. The term is based on the Greek word autós, meaning self. Bleuler was describing people with schizophrenia. These people had withdrawn into themselves.

Hans Asperger and Leo Kanner studied autism in the 1940s. The two researchers described what we know as autism today. They observed children with traits similar to today’s description of ASD. 

For much of the 20th century, people saw autism in terms of its effects on intelligence. It was often blamed on parenting skills. More accurate research has come out since the 1980s. This research has shaped current knowledge of ASD.


  1. About Rett syndrome. (n.d.). Retrieved from https://www.rettsyndrome.org/about-rett-syndrome
  2. Asperger syndrome information page. (2017, May 23). Retrieved from https://www.ninds.nih.gov/Disorders/All-Disorders/Asperger-Syndrome-Information-Page#disorders-r1
  3. Autism spectrum disorder (ASD): Data and statistics. (2017, March 10). Retrieved from https://www.cdc.gov/ncbddd/autism/data.html
  4. Autism spectrum disorder fact sheet. (2017, December 6). Retrieved from http://www.ninds.nih.gov/disorders/autism/detail_autism.htm#268313082
  5. Baron-Cohen, S., Bowen, D. C., Holt, R. J., Allison, C., Auyeung, B., Lombardo, M. V., ... & Lai, M. C. (2015). The “reading the mind in the eyes” test: Complete absence of typical sex difference in ~400 men and women with autism. PLoS One, 10(8). Retrieved from http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0136521
  6. Differential diagnosis. (n.d.). Retrieved from https://www.autism-society.org/what-is/diagnosis/differential-diagnosis
  7. Gender and autism. (n.d.) The National Autistic Society. Retrieved from http://www.autism.org.uk/about/what-is/gender.aspx
  8. Gottbetter, T. (2013, August 20). DSM-V and how it affects the diagnosis of Asperger’s disorder. Optimum Performance Institute. Retrieved from https://www.optimumperformanceinstitute.com/aspergers-treatment/dsm-v-and-how-it-affects-the-diagnosis-of-aspergers-disorder
  9. Hughes, E. (2015). Does the different presentation of Asperger syndrome in girls affect their problem areas and chances of diagnosis and support?. Autonomy, the Critical Journal of Interdisciplinary Autism Studies, 1(4). Retrieved from http://www.larry-arnold.net/Autonomy/index.php/autonomy/article/view/AR17
  10. Lai, M. C., Lombardo, M. V., Ruigrok, A. N., Chakrabarti, B., Auyeung, B., Szatmari, P., ... & MRC AIMS Consortium. (2017). Quantifying and exploring camouflaging in men and women with autism. Autism, 21(6), 690-702. Retrieved from http://journals.sagepub.com/doi/abs/10.1177/1362361316671012
  11. Mandal, A. (2018, February 16). Autism history. Medical and Life Sciences News. Retrieved from https://www.news-medical.net/health/Autism-History.aspx
  12. Related conditions. (n.d.). Retrieved from https://www.autism-society.org/what-is/diagnosis/related-conditions
  13. Robison, J. E. (2017). Kanner, Asperger, and Frankl: A third man at the genesis of the autism diagnosis. Autism, 21(7), 862-871. Retrieved from http://journals.sagepub.com/doi/abs/10.1177/1362361316654283
  14. Statistics. (n.d.) Asperger’s Network Support. Retrieved from http://aspergersmn.org/history-traits-answer-mn/statistics-answer-mn
  15. Vaccine safety. (2015, October 27). Retrieved from https://www.cdc.gov/vaccinesafety/vaccines/mmrv-vaccine.html
  16. What is Asperger’s syndrome? (n.d.) Autism Society. Retrieved from http://www.autism-society.org/what-is/aspergers-syndrome
  17. What is autism?: Causes. (2015, July 15). Retrieved from http://www.autism-society.org/what-is/causes
  18. What is stimming? (n.d.). AppliedBehaviorAnalysisEdu.org. Retrieved from https://www.appliedbehavioranalysisedu.org/what-is-stimming