Autism spectrum disorder (ASD) is a developmental disorder characterized by the challenges it causes with social interaction, language skills, nonverbal communication; repetitive patterns of behavior; and the display of unique and highly specific strengths and differences compared with other people, explains Jeremy Veenstra-Vanderweele, MD, director of the division of child and adolescent psychiatry at NewYork-Presbyterian Morgan Stanley Children's Hospital in New York City. Typically individuals on the autism spectrum will experience a combination of some or all of those symptoms, with varying degrees of severity. That means the condition can appear to be very different from person to person.

Some people with autism go to college or hold a steady job, while others will have difficulty with daily living. Roughly 40 percent of people with autism are nonverbal and about one-third also have an intellectual disability of some kind, according to Autism Speaks.

A wide variety of medical conditions are also associated with autism, including seizures, sleep problems, attention deficit hyperactivity disorder (ADHD), and gastrointestinal disorders.

The general public and those who work with people with autism need to be aware of and sensitive to the wide variability of experiences of those who are on the spectrum, notes Thomas Frazier II, PhD, chief scientist at Autism Speaks, an autism advocacy organization. "The first step to understanding what autism is means focusing on each individual's set of difficulties and challenges and needs. You have to think, if you are a provider: 'How can I go about designing a plan to help them?'"

Everyone with autism has different cognitive abilities, social and communication skills, and behavior struggles, Dr. Frazier adds. "Everybody's different, and you have to talk to the person and be empathetic."

There's Only 1 Diagnosis for ASD, but It Includes Individuals With a Range of Disorders

In 2013, the American Psychiatric Association (APA) combined what were once four separate diagnoses under the umbrella of autism spectrum disorders — ASD for short. In its report, the APA stated that the new definition for ASD represents "a new, more accurate, and medically and scientifically useful way of diagnosing individuals with autism-related disorders."

The association concluded that previous diagnoses were not consistently applied across-the-board from clinic to clinic, and it made more sense for everything to fall under one general ASD classification.

It's important to recognize, however, that many individuals living today with autism were given those diagnoses before 2013 and may still identify with those terms. Understanding the old diagnoses can help explain the range of symptoms and prognoses to expect for people with autism.

Those diagnoses were:

Autistic Disorder This diagnosis was the "classic" case of autism. Symptoms could include any combination of language challenges, repeating specific behaviors, learning disabilities, or problems with speech and nonverbal communication. Someone with this diagnosis might have also had very unique strengths and differences from others.

Asperger's Syndrome People with this diagnosis were on the "high functioning" end of the ASD spectrum. Usually people with Asperger's have difficulty with social interaction and show signs of repetitive behaviors. These people may also have problems with motor development. But people who were given this diagnosis typically did not have serious delays with language or other kinds of cognitive development.

Childhood Disintegrative Disorder This diagnosis was also called Heller's syndrome. It is a rare condition that was defined by late-onset symptoms appearing at around age 3 or later. Symptoms included delays in motor skills, social interaction, and language. It was also considered a type of "regressive autism," which means a child might appear to develop normally at first, but later develop autism symptoms.

Pervasive Developmental Disorder — Not Otherwise Specified (PDD-NOS) Sometimes this condition was labeled "subthreshold autism" because a person may have some of — but not all — the characteristics of autism, and these might be fairly mild symptoms, according to Autism Speaks.

Learn More About Why Doctors No Longer Diagnose 4 Types of Autism

Signs and Symptoms of Autism

The signs of autism vary widely. But there are red flags parents and caregivers of babies and young children can look for.

For babies and toddlers, the first sign of autism may be difficulty responding to their names when they are called, Frazier says. "A lot of babies and toddlers who don't make appropriate eye contact, or who don't engage in joint attention with others, with a shared experience of observing an object or an event," may have autism, he adds.

Displaying repetitive motor movements and behaviors are other key warning signs to watch out for in children.

Dr. Veenstra-Vanderweele concurs that a person with autism may have trouble with "two-way communication" and may not respond much at all to someone addressing them. Sometimes people on the spectrum also exhibit an almost obsessive attention to very specific details.

"There was one child I worked with who was so interested in sharks I couldn't have a conversation about anything else that didn't include sharks," Veenstra-Vanderweele recounts. "Some of those kids can't leave a topic behind in conversation. And sometimes they can't be motivated to do something or engage with something that doesn't involve that very specific, restricted interest."

According to the Centers for Disease Control and Prevention (CDC), common signs that a child may have ASD include:

Not pointing at objects when interested in them
Not looking at things someone else points to
Difficulty relating to others; or being interested in other people but not knowing how to talk, play, or interact
Avoiding eye contact and wanting to be by themselves
Difficulty understanding the feelings of others and talking about their own
Not enjoying being held or cuddled
Seeming unaware when people talk to them, but noticing other sounds
Repeating words or phrases said to them
Difficulty expressing their needs
Not playing "pretend" games
Repeating actions over and over again
Difficulty switching to new routines
Unusual responses to sensory stimuli, such as odors, sounds, or flavors
Loss of skills they used to have

Learn More About Autism Symptoms in Babies, Toddlers, Children, and Adults

Causes and Risk Factors of Autism

The medical community has yet to definitively explain why autism develops in some individuals and not in others. But there are several risk factors, both genetic and environmental, that have been found to be associated with the disorder, Veenstra-Vanderweele says.

For instance, autism sometimes runs in families. And in about 15 to 20 percent of children on the autism spectrum, a single gene or chromosome disorder is responsible for the syndrome's development, according to the National Fragile X Foundation.

The most common is fragile X syndrome, caused by mutation of a gene called FMR1 that regulates a protein thought to be involved in the development of synapses, the brain's cell-to-cell communication system, notes MedlinePlus.

About 1 in 3,600 to 4,000 males and 1 in 4,000 to 6,000 females are born with fragile X syndrome.

There are other potential risk factors. Prenatal exposure to some medications, premature birth, low birth weight, as well as the age of an individual's parents, may raise the odds. But a lot more research needs to be done to better understand those connections, Veenstra-Vanderweele says.

One factor that has been proven not to increase the risk of autism, is vaccination. A lot of public attention was paid when false information came out in the late 1990s that linked vaccination to autism, a link that has subsequently been disproved in multiple studies. The American Academy of Pediatrics has compiled a list of dozens of studies that found no connection between childhood vaccines (or the ingredients in them) and autism.

Parents and pediatricians need to work together to communicate to everyone the fact that vaccinations do not cause autism, Veenstra-Vanderweele says. Not vaccinating children puts those children at higher risk for diseases and increases the risk of those diseases spreading to others.

Researchers have looked into a relationship between autism and prenatal cigarette smoking, per a study published in November 2018 in Translational Psychiatry,

as well as autism and delivery by cesarean section, per a review published in August 2019 in JAMA Network Open.

While research has shown associations, the evidence for any causal link is lacking and more research is needed.

Learn More About the Causes and Risk Factors for Autism

How Is Autism Diagnosed?

There is no blood test or genetic profile (yet) that allows a doctor to conclusively make an autism diagnosis. Frazier says that diagnosing ASD involves looking at a child's behavior and overall development.

Most pediatricians regularly screen all children for developmental delays and disabilities between 9 months and 30 months. But if your child has a sibling with ASD or if you or another caregiver has concerns that certain symptoms may be signs of autism, you can talk to your child's doctor at any time (or your doctor, if the concerns are about yourself).

Initial autism screening usually involves checking that a child is meeting developmental milestones or if there are developmental delays. This could involve asking a parent questions about the child or interacting or playing with the child to see how he or she behaves.

If an initial screening indicates the possibility of autism, a comprehensive diagnostic evaluation is the next step. Such an evaluation involves a more thorough examination of a child's behavior, vision and hearing exams, and genetic and neurological tests. In some cases, your doctor may refer a child to a specialist for further tests, notes the CDC.

It's important to know that autism cannot develop in adults, but in some cases individuals with the disorder were not diagnosed as children or were misdiagnosed. So, though it doesn't happen often, the disorder may be diagnosed in adults. If you have concerns about symptoms you're experiencing, talk to your doctor about the right course to get screened, says the National Institute of Mental Health (NIMH).

Learn More About How Autism Is Diagnosed

Treatment and Medication Options for Autism

Treatment for autism typically includes a combination of behavioral therapies, dietary approaches, medications, and complementary and alternative medicine approaches that best meet the needs of the individual.

There are no medications that cure autism — or make all of its symptoms disappear. In some instances, however, medications can help manage symptoms, such as irregular energy levels, inability to focus, depression, or seizures, notes the CDC.

Talk with your child's doctor before giving her or him an alternative therapy for autism symptoms. Melatonin may help with sleep problems, according to a meta-synthesis published in May 2017 in Pharmacotherapy.

But there's no clear evidence for other remedies, such as omega-3 fatty acids, or acupuncture, and some, like hyperbaric oxygen or chelation, can be dangerous, notes the National Center for Complementary and Integrative Health.

About 1 in 3 parents of a child with ASD try alternative remedies, but 10 percent may be using dangerous types, the CDC warns.

Because autism varies so much from person to person in terms of symptoms and abilities, treatments must be customized, Frazier explains. But in general, early intervention is typically better, and all treatment tends to involve the child's family working closely with a team of doctors and caregivers.

It's important to understand that in the United States, all children with autism have the right to receive therapy and individualized education, according to federal law (under the Individuals with Disabilities Education Act), once they obtain an individualized education program (IEP), which describes that individual's disabilities and the educational program that has been designed to meet his or her needs, notes Autism Speaks.

Learn More About Treatments and Therapies for People With Autism

Prognosis

The prognosis for people with ASD is as individual as they are. The extent of their developmental delays and the quality of the interventions they received — particularly early interventions — can make a difference in their outlook for education, work, and independent living.

Complications of Autism

People with ASD face higher risk for psychiatric disorders, immune-related problems, metabolic conditions, and movement disorders, according to a 2015 Kaiser Permanente study that compared the health records of 1,057 adults with ASD to 15,070 without the disorder, published in October 2015 in Autism.

Adults with ASD had higher risk for schizophrenic disorders, obsessive-compulsive disorder, bipolar disorder, ADHD, anxiety and depression.

They also faced higher odds for allergies, asthma, diabetes, heart disease, hearing loss, sleep problems, obesity and cerebral palsy. People with autism are also more likely to experience seizures and to have dental problems and gastrointestinal symptoms, notes the Autism Research Institute.

In addition, ASD-related social, communication, and behavioral challenges can contribute to difficulties learning in school, problems in employment and living independently, social isolation, and stress, according to Mayo Clinic.

Autism in Adults

As mentioned above, you cannot get autism as an adult. But because there has been less awareness historically about screening for and diagnosing autism, there are individuals who are diagnosed with autism in adulthood, whose condition was missed when they were younger.

And while some people with the disorder who are high-functioning, or those for whom treatment has allowed them to manage their symptoms, go on to college or vocational schools and enter the workforce — others with autism continue to need treatment and support through adulthood.

And once school ends, the transition into adulthood can be difficult for individuals with autism, especially for those who are not high-functioning.

Veenstra-Vanderweele adds that another big challenge, once schooling is over, can be the cost of support. Federal funding is available to children with autism for treatment and educational programs. Though some financial assistance is available to adults with autism (Medicaid and Social Security benefits), that assistance does not always cover the full costs of a person's treatment and basic living needs, particularly for individuals who are dependent on a parent or caregiver, according to Autism Speaks.

Talking with school guidance counselors, school aides, healthcare providers, and other clinicians who manage care for people with autism can help you determine the best next step in the transition from childhood into adulthood, notes Autism Speaks.

Additionally, for those entering the workforce and for those with autism who are already adults, many other resources are available with information about financial assistance, services, and other support systems to meet an individual's needs.

Learn More About Living With Autism as an Adult

Research and Statistics: Who Has Autism?

Overall, between 1 and 2 percent of people have ASD. It occurs in all racial and ethnic groups, but it's about 4 times more prevalent in boys than in girls. Researchers suspect part of this sex difference is because girls' ASD symptoms may be different and less obvious than those of boys. But there's also evidence that the female brain is somehow shielded from ASD development more than the male brain — and that autism may develop in boys with fewer genetic mutations. Thanks to heightened awareness and more widespread screening, the number of children diagnosed with ASD by age 8 has increased — rising from 1 in 150 in the year 2000 to 1 in 54 in 2016, according to the CDC.

Researchers are currently investigating ASD's origins and early symptoms in an effort to make earlier diagnosis and intervention possible. Scientists are also looking at interventions, the overall health of people with ASD, as well as the health of their caregivers. Some notable areas of research include:

Causes The largest study in the United States looking at risk factors for ASD is currently underway in six diverse communities across the country, notes the CDC.

Research into other risk factors includes a Canadian study published in August 2020 in the journal Nature Medicine, that found that women who used cannabis during pregnancy were 50 percent more likely to have a child with autism than those who did not.

Earlier Diagnosis Researchers are taking a close look at early indicators of ASD in babies. The goal: Early diagnosis and earlier intervention so children with autism can learn more language and social skills, per a study published in January 2015 in the Journal of Autism and Developmental Disorders.

Parents' Experiences Caregivers of children and teens with ASD work hard around the clock, like parents of kids with other chronic health conditions, but they may feel more stress and enjoy less social support, found a 2018 study published in Clinical Practice and Epidemiology in Mental Health.

"We need to figure out ways to try to best educate different segments of the population and help them accept and accommodate people with autism," Frazier says. "What is the best way to train police in dealing with people with autism? How do we train employers to do a better job? How do we make living environments that are conducive to people [with autism]? How do we have hospitals that are sensory friendly?

"I think there is a lot of research and more that will be done that will look at how we make these societal improvements," he says. "It's important to keep generating awareness and understanding and [so we] all do better to help people living with this."

There is an enormous opportunity for research when it comes to understanding the genetic risk factors for autism as well, Frazier adds.

Conditions Related to Autism

A wide variety of conditions that affect mental and physical health are related to autism in children and in adults. According to Autism Speaks, these include:

Gastrointestinal (GI) problems
Epilepsy
Feeding issues
Disrupted sleep
Attention-deficit hyperactivity disorder (ADHD)
Anxiety
Depression
Obsessive compulsive disorder (OCD)
Schizophrenia
Bipolar Disorder

As noted above, people with autism also face higher risk for allergies, asthma, diabetes, heart disease, hearing loss, sleep problems, obesity, and cerebral palsy.

Resources We Love

Autism Society

One of the world's most-visited websites for autism spectrum disorders, this site is the online presence of the Autism Society of America, an organization founded in 1965 to share high-quality information, and offer support and advocacy for with people on the autism spectrum and their families. You'll find a comprehensive online resource database, Autism Source, access to the group's National Contact Center (800-3-AUTISM) for info and service referrals, and ways to connect with Autism Society affiliates across the United States. One thing we love: Extensive autism information in Spanish, accessible from the homepage by clicking on "¿Que es Autismo?"

Autism Speaks

This inspiring organization promotes acceptance, support, and solutions for the needs of people on the autism spectrum and their families. One notable feature: Access to the organization’s Autism Response Team (ART), a hotline with a trained staff that provides personalized information and resources to people with autism, their families, friends, teachers, and social workers. Autism Speaks actively supports and promotes research into autism's causes, early diagnosis, better treatment of autism-related health conditions, and more. You can get involved, by using the website's "Participate in Research Search" to find studies and surveys looking for participants.

National Institute of Neurological Disorders and Stroke (NINDS)

A branch of the National Institutes of Health, NINDS provides up-to-date and easy to understand explanations of the science behind autism and other brain disorders, as well as treatments and a round-up of current research. One useful feature: Links to other NIH branches for more information about health conditions often experienced by people with autism and to other autism research and service organizations. You'll also find fascinating and useful background information, including Brain Basics: Know Your Brain, an illustrated guide to how the brain works.

Spectrum Inspired

A passion project started by four women (all moms; one is an ER nurse, one is a special education teacher, and two of them have children with special needs), Spectrum Inspired features candid photography and heart-felt stories of people with autism and their families. You can browse and purchase Spectrum Inspired magazine, as well as read and view the site's blog full of stories and beautiful, sensitive photo essays.

The Arc

With more than 600 local chapters, The Arc — one of America's longest-running support and advocacy organizations for people with intellectual and developmental disabilities (I/DD) — tackles big, important issues for people with I/DD, like employment, treatment by law enforcement and the criminal justice system, and obesity and chronic disease. One valuable, online resource: Future Decisions, a detailed guide to help families and people with I/DD plan for the future.

The Color of Autism Foundation

With the goal of "ending the stigma of autism spectrum disorders in communities of color," this Michigan-based nonprofit offers support to African American families with children on the autism spectrum, including online training for parents on how to advocate for their needs.

Atypical Familia

A personal family blog about autism, special needs travel, work-life balance, family entertainment, and more. The blog by mom and writer Lisa Quinones-Fontanez is a follow-up to her blog AutismWonderland, which chronicled the early years of her son Norrin, who has autism. That award-winning blog was recognized for boosting autism awareness in the Latinx community. Atypical Familia continues the tradition. One moving post: Teaching My Son About Puerto Rican Pride.

Additional reporting by Sari Harrar.

Editorial Sources and Fact-Checking

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What is Autism Spectrum Disorder? Centers for Disease Control and Prevention. March 25, 2020.
After the Autism Diagnosis: What You Need to Know About Genetic Testing. Fragile X Foundation. May 20, 2019.
FMR1 gene. U.S. National Library of Medicine. April 2020.
Vaccine Safety: Examine the Evidence. American Academy of Pediatrics. January 26, 2017.
Caramaschi D, Taylor AE, Richmond RC, et al. Maternal Smoking During Pregnancy and Autism: Using Causal Inference Methods in a Birth Cohort Study. Translational Psychiatry. November 29, 2018.
Zhang T, Sidorchuk A, Sevilla-Cermeño L, et al. Association of Cesarean Delivery With Risk of Neurodevelopmental and Psychiatric Disorders in the Offspring: A Systematic Review and Meta-Analysis. JAMA Network Open. August 28, 2019.
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Autism Spectrum Disorder (ASD): Treatment. Centers for Disease Control and Prevention. September 23, 2019.
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Related Disorders. Autism Research Institute.
Autism Spectrum Disorder: Symptoms and Causes. Mayo Clinic. January 6, 2018.
What Are My Rights? Autism Speaks.
Transition Tool Kit. Autism Speaks.
Data & Statistics on Autism Spectrum Disorder. Centers for Disease Control and Prevention. March 25, 2020.
Research on Autism Spectrum Disorder. Centers for Disease Control and Prevention. September 24, 2019.
Corsi D. Maternal Cannabis Use in Pregnancy and Child Neurodevelopmental Outcomes. Nature Medicine. August 2020.
Rowberry J, Macari S, Chen G, et al. Screening for Autism Spectrum Disorders in 12-Month-Old High-Risk Siblings by Parental Report. Journal of Autism and Developmental Disorders. January 2015.
Picardi A, Gigantesco A, Tarolla E, et al. Parental Burden and its Correlates in Families of Children with Autism Spectrum Disorder: A Multicenter Study with Two Comparison Groups. Clinical Practice and Epidemiology in Mental Health. July 2018.
Medical Conditions Associated With Autism. Autism Speaks.

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What Is Autism? Symptoms, Causes, Diagnosis, Treatment, and Managing It