Autism spectrum disorder is a neurological and developmental disorder that affects how a person learns, communicates, interacts socially, and behaves. Autism can cause delays or differences in learning, social skills, and communication. Many people with autism also experience sensory sensitivities, seizures, gastrointestinal problems, anxiety, depression or other mood disorders, and attention-deficit/hyperactivity disorder (ADHD).

Understanding Autism

Autism is described as a spectrum because its effects can range from mild to debilitating. People with autism have different support needs — some are mostly independent, while others need lifelong assistance with daily tasks. Almost one-third of autistic people speak only a little or not at all, although many use nonverbal forms of communication. A little over one-third also have intellectual disabilities, whereas others have average or above-average intelligence.

Even with these differences, most people with autism share challenges with communication, understanding social cues, connecting with others, and handling changes in routines. Repetitive behavior and intense interest in specific topics or objects are also common.

Read more about behaviors and other symptoms of autism.

Terms Related to Autism

Autism spectrum disorder now includes several conditions that were diagnosed separately until 2013, when the American Psychiatric Association published the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). The DSM-5 combined diagnoses like Asperger syndrome, childhood disintegrative disorder, and pervasive developmental disorder-not otherwise specified (PDD-NOS) into one diagnosis — autism spectrum disorder. Health professionals now use “autism spectrum disorder” instead of these old terms.

When talking about autism, some people prefer person-first language, such as “child with autism,” while others prefer identity-first language, like “autistic person.” It’s always best to ask someone what language they prefer.

Read more about the former and current classification of autism.

How Does A Child With Autism Behave?

Because autism is a spectrum, children with autism can behave in very different ways. Still, some common signs may appear in early childhood. These include:

• Not showing facial expressions by around 9 months old
• Not responding to their name or babbling by 9 months (not due to hearing loss)
• Not engaging in pretend play by age 4
• Avoiding eye contact
• Getting very upset when routines change
• Repeating words or phrases past the typical age
• Playing in the same way over and over
• Having strong or obsessive interests
• Repeating movements, such as hand-flapping or rocking

The History of Autism

Before the 20th century, autism wasn’t distinguished from mental illness, epilepsy, or other neurological and developmental disorders.

The word “autism” — from the Greek word “autos,” meaning “self” — was first used in a 1912 article by Swiss psychiatrist Paul Eugen Bleuler, which described people with schizophrenia who seemed deeply withdrawn. For many years, autism remained classified as a subset of schizophrenia in the DSM.

In 1943, American psychiatrist Leo Kanner published an article about children who displayed high intelligence, preferred to be alone, and had what he called “an obsessive insistence on persistent sameness.” Kanner termed this condition “early infantile autism” and suggested that cold, emotionally distant mothers might play a role.

In 1944, Austrian pediatrician Hans Asperger described boys who were highly intelligent and socially isolated, with specific, obsessive interests and poor motor skills. His work was published in German and didn’t have a wide audience at that time. Meanwhile, in Nazi Germany, people with mental disabilities were targeted by eugenics policies, including forced euthanasia.

In the 1960s, Austrian-American child psychologist Bruno Bettelheim popularized the theory that “refrigerator mothers” caused autism by failing to show enough affection. Parents were told they were to blame for their children’s diagnosis.

Then, in 1964, Bernard Rimland, an American research psychologist and the father of an autistic child, published a book that rejected Bettelheim’s theories and made the case for autism as a biological condition. In 1969, Rimland helped found what is now known as the Autism Society.

Bettelheim’s refrigerator mother theory was discredited within a few years. By the 1980s, research supported Rimland’s view that autism is rooted in genetics and brain development.

In 1980, autism was listed as a separate diagnosis from childhood schizophrenia in the DSM-III. During the ’80s, the work of Hans Asperger was widely translated and published, shedding more light on the autism spectrum. In 1991, the U.S. government recognized autism as a category of special education, requiring schools to evaluate and support autistic children. Asperger syndrome was added to the DSM-IV in 1994.

During the 1990s, Norwegian-American psychologist Ole Ivar Lovaas applied a treatment called applied behavior analysis to people with autism. Some studies report benefits from this method, but research reviews don’t show it to be clearly better than other therapies.

In 1998, autism research faced a major setback when British doctor Andrew Wakefield published an article suggesting a link between the measles-mumps-rubella (MMR) vaccine and autism based on 12 children he studied. The study was quickly proven false. Wakefield was found to have manipulated data and was accused of conflicts of interest. Wakefield’s article was retracted in 2010, and he lost his medical license.

In 2013, the DSM-5 used the term “autism spectrum disorder” to describe a range of related developmental disabilities under two categories: social communication and restricted or repetitive behaviors. Conditions like Asperger syndrome are no longer separate diagnoses but are considered part of the broader autism spectrum.

Many famous figures in history are believed to have had autism spectrum disorder, although no one knows for sure. Examples often mentioned include Mozart, Michelangelo, Sir Isaac Newton, Charles Darwin, Emily Dickinson, and Albert Einstein.

How Common Is Autism?

In the United States, about 3.2 percent of 8-year-old children, or 1 in 31, have autism. The disorder is more difficult to diagnose in adults, making it harder to estimate how many live with autism. Worldwide, around 2 percent of people are believed to have autism spectrum disorder.

The Centers for Disease Control and Prevention (CDC) reports that boys are over three times more likely than girls to be diagnosed. However, according to UCLA Health, new research shows that symptoms of autism may look different in females, which can delay or prevent diagnosis. Autism can affect people of any race, background, or income level, but some groups may be diagnosed later or less often than others.

How Is Autism Diagnosed?

There’s no single conclusive test for autism. Screenings at well-child visits, school evaluations, and medical diagnoses can differ.

• Screening at doctor visits — Pediatricians use checklists to flag early signs of autism. These screenings can’t confirm a diagnosis but may lead to further evaluation.
• School evaluations — Teams of educators assess how autism may affect learning and classroom needs. This process determines eligibility for special education services, but it’s not a medical diagnosis.
• Medical diagnosis — Specialists such as developmental pediatricians, child psychologists, child psychiatrists, or neuropsychologists make a formal diagnosis. They review a child’s developmental history, observe behavior, and test cognitive abilities, language skills, and age-appropriate physical skills.

Some children may show signs of autism in the first year of life, but in the U.S., the average age of diagnosis is 3 years and 11 months. Older children and teens may be referred for evaluation by teachers. Diagnosing autism in adults is more complex.

Read more about how autism is diagnosed.

Join the Conversation

On MyAutismTeam, people share their experiences with autism spectrum disorder, get advice, and find support from others who understand.

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