9 Facts About Autism Spectrum Disorder

Children can be very young when diagnosed

It's possible for children as young as 18 months to be diagnosed with ASD, according to MedlinePlus. But most diagnoses occur at 24 months or older, at which point the diagnosis is considered reliable.

"Before that, kids with autism will show deficits in social communication, but it's appropriate for their age," Alycia Halladay, PhD, chief science officer at the Autism Science Foundation in New York City, told Health.

There's no medical or blood test for ASD, so healthcare providers typically evaluate a child's behavior through a developmental screening and a comprehensive diagnostic evaluation, which can include hearing, vision, and neurological tests. The provider may also recommend a follow-up visit to a specialist, such as a developmental pediatrician.

There's a wide range of symptoms

ASD symptoms can vary widely, depending on the individual. For some people, symptoms of the disorder are mild; for others, they may be more pronounced.

In general, symptoms of ASD tend to involve communication skills and social behaviors, such as difficulty recognizing others' intentions and feelings or not making eye contact, according to Autism Speaks.

Kids with ASD may also repeat certain behaviors (such as flapping their hands) over and over again, or they may become obsessed with a particular toy. Lack of verbal skills is another one of the most well-known symptoms—approximately 40% of people are nonverbal, according to Autism Speaks—but this does not happen in every case.

Other signs of ASD in children include being overly sensitive to noise, throwing intense tantrums, not responding when spoken to, not pointing at interesting objects, or not playing "pretend" games by 18 months.

Prevalence seems to be growing

According to a 2021 MMWR Surveillance Summaries report, the prevalence of ASD has risen from one in 150 children being diagnosed to one in 44, since 2000. There's disagreement among experts about whether or not this increase reflects more people actually having ASD or more diagnoses due to increased awareness and screenings.

"I think it could be a combination of prevalence and diagnosis," Alexandra Perryman, a board-certified behavior analyst and lead clinician at the Western Psychiatric Institute and Clinic of UPMC Theiss Early Autism Program, told Health. "The criteria for diagnosis is changing, and that's led to more children being diagnosed."

Still, more research is needed to determine what exactly is behind these figures.

Boys are more likely to be diagnosed

Autism spectrum disorders are about four times more common in boys than in girls. One in 27 boys were reported to have ASD, compared to one in 116 girls, according to Autism Speaks. And although boys do tend to be diagnosed earlier and more often than girls, there's growing evidence that the number of ASD cases in girls is under-diagnosed.

A May 2018 study published in the Journal of Autism and Developmental Disorders explored sex-based differences when it came to ASD presentation in girls. The researchers discussed the disparity of the diagnosis gap between girls and boys but also noted how girls are known to have camouflaged symptoms—signs of ASD that are missed in evaluations—leading to their being under-diagnosed.

Fewer ASD screenings for young girls may be due in part to what people expect of young boys vs. girls, said Perryman. "A lot of times, people think 'Girls are shy, it's okay if they're not talking right now, she prefers to just play by herself.' And boys, the stereotype is they should be playing with friends and running around and roughhousing, and when they see a kid not wanting to play with his peers, it's more noticeable."

Autism may begin before birth

Scientists don't know exactly what causes autism. Most experts agree that a combination of genetic and environmental factors increase a child's risk of developing ASD, according to MedlinePlus.

Additionally, there's emerging evidence that children may start to develop ASD before they're born. "This is a really critical time point," said Dr. Halladay. "We know it's pre-birth because we have identified cells in brains of people with autism that are different. Those cells develop before the baby is born."

Older parents have a higher chance of having a child with ASD, according to Autism Speaks, and a person is more likely to have ASD if they have a sibling with the disorder.

People with autism are more likely to have other health conditions

People with autism spectrum disorder have a greater risk of contracting other health conditions, as well. Researchers found that many adults with ASD may have other conditions such as constipation, obesity, insomnia, and epilepsy, according to a 2021 study published in the Review Journal of Autism and Developmental Disorders.

Also, ASD may be associated with certain genetic conditions, such as Angelman syndrome, a developmental disorder; Rett syndrome, a rare neurological disorder; and fragile X syndrome, which causes intellectual challenges, according to the CDC. People with ASD may also be more prone to issues such as anxiety, attention-deficit/hyperactivity disorder (ADHD), depression, sleeping problems, allergies, and stomach issues.

Vaccines do not cause ASD

Vaccines do not cause ASD, a 2021 Brown University Child and Adolescent Behavior Letter reported.

Although people may continue to disagree, study after scientific study has confirmed that no link exists.

The theory first began after a small 1998 study claimed to find a link between autism and the measles, mumps, and rubella (MMR) vaccine. But that study was deemed flawed and retracted by the journal that originally published it.

Early intervention is key

There's no cure for ASD,but early intervention may help people thrive despite having the condition.

Applied behavioral analysis (ABA) and occupational, speech, and physical therapies are frequently used in treatment. ABA has proven to be an effective approach for determining root causes of behavior. "It works by identifying the reasons why kids are engaging in behaviors," said Perryman. For example, throwing tantrums and flapping hands are often triggered by the frustration of not being able to express that you're hungry.

Also, therapy includes teaching methods of social interaction, such as making better eye contact. "The earlier the child is treated, the more gains that are seen with communication and social skills," said Perryman.

Medications, such as antidepressants, anti-seizure medication, or stimulants, are sometimes prescribed to treat conditions that may occur alongside ASD, such as anxiety, ADHD, epilepsy, or depression.

Evaluations and interventions

If you think your child may have ASD, screening and testing can help determine if they have symptoms of the disorder.

"Everyone is entitled to services, regardless of age," said Dr. Halladay. The CDC has provided information about the screening process, included the tools that may be used (e.g., questionnaires).

Interventions can be provided through community or healthcare settings and school districts. There are services for ASD screening and diagnosis that can be provided for free, according to Autism Speaks. However, some parents choose private services, which do have fees attached.

Overall, knowing the signs of ASD is important for diagnosis, treatment, and prognosis.