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What is autism spectrum disorder (ASD)?

Autism spectrum disorder, also known as ASD, is a complex disorder of very early brain development that is approximately four times more common in boys than girls. Different children can be affected in very different ways, ranging from mild to severe, but they share two main categories of symptoms:

  • Difficulty with social communication and social interactions
  • Repetitive behaviors and restricted or unusual interests, including sensory symptoms such as heightened sensitivity to noise, touch, or smell

Autism spectrum disorder is a neurodevelopmental condition, meaning it affects the way your child develops and behaves. The number of children being diagnosed with ASD has been increasing since the 1980s, in part because clinicians and families are better able to recognize it.

ASD affects children differently and to varying degrees. An in-depth evaluation by specialists with expertise in child development and behavior can help identify strengths that can be harnessed to help your child learn, as well as skills that they will most need to work on. It’s also important to keep monitoring your child, because the characteristics of their behavior and development may shift as children get older.

ASD was previously recognized as several separate disorders, including autistic disorder, pervasive developmental disorder-not otherwise specified (PDD-NOS), and Asperger’s disorder. Based on their shared symptoms, these were merged under a single ASD diagnosis with the May 2013 publication of the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5).

Estimates have varied widely, but 2023 statistics from the U.S. Centers for Disease Control and Prevention (CDC) identified 1 in 36 children as having a diagnosis of ASD. The true number is hard to know, since different studies were conducted and interpreted in different ways.

While there’s currently no “cure” for autism spectrum disorder (ASD), our understanding is evolving rapidly. Early diagnosis and therapy can be very helpful in helping children with ASD gain new skills.

Watch: How is each person with autism unique?

Dr. Sarah Spence, a pediatric neurologist and co-director of Boston Children's Autism Spectrum Center, discusses the nuances of ASD.

Autism Spectrum Disorders | Symptoms & Causes

What are the symptoms of autism spectrum disorder?

ASD affects every child differently. It’s not possible to simply say that one child is on the “low” end of the autism spectrum and another at the “high” end. Instead, each child will have different skills and different struggles.

Although the symptoms of autism vary in severity, the core behaviors that describe ASD are:

  • Difficulty with social communication and social interaction including: verbal and nonverbal communication, trouble developing and maintaining relationships, and deficits in initiating and responding to social cues
  • Unusual, restricted, or repetitive behaviors (also called "stereotyped" behaviors or stereotypies), intense interests, and/or unusual sensory behaviors

The core symptoms of ASD may show up in different ways. Some children with ASD are nonverbal but can learn to communicate through other means. Others speak easily but aren’t good at using language to communicate with others. Some have unusual-looking behaviors; others do not. Some have severe cognitive impairments; others are very intelligent. Some children are easygoing, while others can get easily frustrated and may behave aggressively or injure themselves.

For some children, especially those whose ASD symptoms are less pronounced, symptoms may not be fully appreciated until the middle school years, late adolescence, or young adulthood when social demands increase.

These symptoms typically occur in the first few years of life. You may even notice subtle differences before your child’s first birthday — like not making eye contact, not using gestures, or not responding to her name might be early signs of autism. Sometimes children develop normally at first, but then stop gaining new skills or even begin to lose skills at around 18 to 24 months.

What causes autism spectrum disorder?

Despite a lot of effort in research, the exact causes of ASD are not known. There are most likely different causes in different children. Researchers have identified certain risk factors, such as having a sibling with ASD or an older father, or having certain genetic conditions, but many children with ASD don’t have these factors.

Many studies are showing that whatever the cause, the result is changes in how the connections in the brain are organized. Most scientists also agree that genetics plays a role. Although many different genes and chromosomal changes have been linked with ASD, most genetic causes are still unknown. Some of these DNA changes may be inherited from parents, while others may occur just in the child. Research at Boston Children’s and elsewhere is exploring how they may contribute to children’s symptoms.

In a small number of cases, a prenatal infection, injury, or other medical condition is thought to be involved in ASD. While it has been suggested that some vaccines may be a cause, a large amount of research shows that vaccines are not associated with ASD.

Autism Spectrum Disorders | Diagnosis & Treatments

Currently, there is no definitive laboratory test for autism spectrum disorder (ASD), though active research is looking for “biomarkers” including genetic tests and brain imaging tests, differences on electroencephalograms (EEGs), and brain imaging tests. (The Autism Research Program is discovering possible biomarkers in babies as young as 6 months.)

For now, though, ASD is diagnosed based on a child’s symptoms and behavior. Usually, the primary care pediatrician will suggest an evaluation by a specialist.

How do I know that my child might have autism?

These are some things parents of children with ASD have noticed in their child:

  • Trouble interacting or communicating with others, including family
  • Trouble speaking or not speaking at all
  • Difficulty expressing his feelings
  • Inability to understand how another person feels
  • Disinterest in physical contact with other people
  • Being withdrawn or preferring to do things by himself
  • Difficulty making friends
  • Avoidance of eye contact
  • Not using gestures such as pointing
  • Saying a word or phrase repeatedly (“echolalia”)
  • Trouble understanding subtleties in language, like sarcasm or jokes
  • Repetitive motions, such as rocking or flapping hands or spinning in circles
  • Unusual rituals or ways of playing with toys
  • A preference for routines, and anxiety when a routine is broken
  • A particular area of interest that consumes a lot of his attention
  • Unusual sensory behaviors such as:
    • Being preoccupied with lights or moving objects
    • Peering at things out of the corner of his eye
    • Dislike of certain kinds of sensory stimulation, such as loud noises
    • Craving other sensory inputs, such as deep pressure on his skin

It’s important to note that typically developing children can also show some of the above behaviors — like flapping their arms when they’re excited or having an unusually strong interest. In children who have ASD, however, these behaviors are more pronounced, more frequent, and tend to get in the way of doing other things. Sometimes other neurodevelopmental disorders, such as language or cognitive disorders, have symptoms that are similar to ASD.

For more information, visit the Center for Disease Control and Prevention’s ASD website. In addition, the Autism Speaks website has a library of videos showing many of the behaviors of ASD.

Testing for autism spectrum disorder in children

At the Autism Spectrum Center at Boston Children’s, ASD assessments include:

  • A medical and neurological examination
  • A review of your child’s cognitive abilities
  • Assessment of your child’s speech and language abilities
  • Observation of your child’s behavior
  • An in-depth conversation with you and your family about your child’s behavior and development
  • Questions about your child’s family history

How is autism diagnosed?

Making an ASD diagnosis is just the beginning. Our clinicians will then perform in-depth evaluations to understand your child’s unique strengths and challenges. This evaluation is crucial for defining what kinds of educational programs and behavioral therapies would be most beneficial.

We may involve a number of specialists, such as child neurologists, developmental behavioral pediatricians, speech-language pathologists, child psychologists and psychiatrists, nurse practitioners, educational specialists, and occupational therapists. Questions you may be asked include:

  • What kind of language skills does your child have?
  • At what age did your child’s symptoms start?
  • Has your child experienced a regression in skills?
  • Does your child have any related cognitive or learning problems?
  • Does your child have any challenging behaviors?
  • Is your child able to pay attention for extended periods?

If appropriate, we may recommend testing to look for related medical concerns based on your child’s history, physical examination findings, and results of cognitive and behavioral testing. For instance, children with ASD often have sleep difficulties, and some develop seizures or epilepsy. Our staff can help make this testing as comfortable as possible for your child — read more about our work to make blood draws easier for children with autism.

Additional tests may include:

  • Hearing and vision screening to see whether your child has a problem that might be contributing to his symptoms
  • Blood lead testing
  • Wood’s lamp exam, a special skin test to screen for tuberous sclerosis
  • Testing for metabolic disorders
  • Neuroimaging (such as MRI)
  • Electroencephalography (EEG)
  • Nutritional evaluation for children who eat very limited foods

Genetic testing for ASD

At Boston Children’s Hospital, we recommend that all children who have been diagnosed with ASD get genetic testing to screen for specific DNA changes that have been linked to ASD and could cause other medical issues. For some families, information from genetic testing can also be important for family planning.

Genetic testing for ASD at Boston Children’s currently includes a chromosomal microarray (CMA) test and testing for fragile X syndrome (in boys). Other genetic testing may be appropriate for children who have particular symptoms. As new genes are found to be important in ASD, some may be added to routine testing.

Behavioral therapies for autism spectrum disorder

If your child has just been diagnosed with autism spectrum disorder (ASD), you may feel you’ve entered a maze, trying to find the best therapies to help your child communicate, have meaningful interactions with others, and develop the skills he needs to reach his full potential.

A variety of intensive behavioral therapies can help children with ASD build language, social, and play skills. Most are provided through programs run by your state and local school system. They include early intervention services for children under age 3 and special education services for children age 3 and older.

We can recommend specific therapies and educational strategies that address your child’s needs while playing to her strengths. For instance, some children are strong visual learners: they may not understand if you explain something verbally, but can instantly grasp a new idea from a picture. Some children may not speak or make good eye contact, but can understand spoken requests and explanations.

In any case, experts agree that therapy should start as early as possible, should be intensive and highly structured, should be done one-on-one or in very small groups, and should actively include families. Often, children receive a combination of different therapies. The effectiveness of any therapy plan should be evaluated frequently, so that changes can be made if needed.

  • Applied behavioral analysis (ABA) is a well-studied, often very effective therapy that identifies behaviors that need to be reduced and those that need to be reinforced. ABA involves practicing new skills repeatedly and creating positive reinforcements. The therapist breaks down new skills into small steps so a child can build more complex skills over time, and customizes the program to each child’s interests, abilities, and behavior.
  • DIR®/Floortime™ is a developmental relationship-based therapy that uses social relationships between caregivers and children to improve a child’s social and communication skills.
  • Other relationship-based therapies include SCERTS® (Social Communication, Emotional Regulation and Transactional Supports) and RDI (Relationship Development Intervention).

Our team at the Autism Spectrum Center includes ASD patient and family educators who will help you choose among developmental and educational therapies and navigate community resources. Learn more here.

Additional therapies for ASD

Your child’s treatment program may also involve a number of other components:

  • Speech-language therapy can help your child understand language and use it to express themselves. At Boston Children’s, extensive services are offered through our Center for Communication Enhancement.
  • Total communication interventions through our Autism Language Program can help your child use any possible means of communication — including speech, symbol systems, gestures, sign language, and innovative technologies.
  • Occupational and physical therapy may develop your child’s fine and gross motor skills (e.g., using her hands or other parts of her body), and dealing with sensory inputs from her environment.

Are there complementary therapies for ASD?

Many families use complementary therapies such as supplements, diet changes, or alternative biomedical interventions. Our team is always happy to discuss these therapies with you, and we would want to be aware of any therapies that you’re considering.

Unfortunately, while there is a lot of anecdotal information available, especially on the Internet, most of these treatments are not well studied. Some medications, herbal therapies, vitamin supplements, or special diets, even if termed “natural” or “herbal,” may be ineffective and even unsafe or harmful if not used properly. For example, many families consider the gluten-free/casein-free diet, but careful implementation is important to avoid nutritional problems that could impact your child’s health and growth.

Are there medications for ASD?

There’s currently no medication for the core symptoms of ASD, although this is an area of active research at Boston Children’s. Medications are, however, often used successfully for symptoms related to ASD, such as irritability, hyperactivity or attention problems, anxiety, or seizures. Often, once these related symptoms are treated, your child can make more progress with behavioral therapies for ASD itself.

Ongoing care

As your child grows up, the therapies that they may need might change. After the initial assessment, we will follow your child closely to:

  • See how they develop and how your child’s therapies are working for them
  • Make new recommendations for education and therapy
  • Watch for any related medical concerns
  • Discuss any questions and concerns you may have

Our goal is for every child with ASD to lead an active and happy life.

Why choose Boston Children’s Hospital?

The Autism Spectrum Center at Boston Children’s has a breadth and depth matched by few other medical centers. By bringing together a wide range of specialists, we can customize care to each child’s and family’s particular needs. Our providers have expertise in developmental behavioral pediatrics, child neurology, neurodevelopmental disabilities, psychology, psychiatry, speech and language, and genetics. The Autism Language Program in the Center for Communication Enhancement is a specialized program for children with ASD and offers the latest technological innovations.

Our team provides diagnostic services, in-depth assessments, close follow-up, and ongoing support, seeking to match your child with the behavioral therapies and teaching approaches that best fit her needs. As your child grows up, we may make new recommendations for therapy, while keeping an eye out for any related medical concerns.

Our clinicians work in Boston at the Longwood campus and the Boston Children’s satellite locations. Our dedicated patient and family educators can help you connect with services in your local community.

We also maintain a very active ASD research and innovation program. As new discoveries are made, we work to translate what we learn into new, effective methods for diagnosis and treatment. We’ve also pioneered many apps to help children communicate and learn.

Contact us

The Autism Spectrum Center at Boston Children’s is best reached through our Call Center.

Boston Children's Hospital
Autism Spectrum Center
Call Center: 617-355-7493
Fax: 617-730-4823

Our coordinator will make the first available appointment based on an intake process that considers your child’s specific needs. For example, children who also have seizures may be directed to a neurologist within the center, while children with speech, language, and communication difficulties may be referred to our Autism Language Program, part of the Center for Communication Enhancement.

Appointments are available in Boston and at many Boston Children’s satellite locations to provide you and your child with care closer to home. The Call Center can help direct you.

Autism Spectrum Disorders | Programs & Services