FILE PHOTO: U.S. Health and Human Services (HHS) Secretary Robert F. Kennedy, Jr. discusses the findings of the Centers for Disease Control and Prevention’s (CDC) latest Autism and Developmental Disabilities Monitoring (ADDM) Network survey, during a press conference at the Department of Health and Human Services in Washington, D.C., U.S., April 16, 2025. REUTERS/Elizabeth Frantz/File Photo

By Nancy Lapid

(Reuters) -Autism diagnoses in the United States have increased significantly since 2000, intensifying public concern over what might contribute to its prevalence. Recent U.S. government data shows that autism diagnoses among 8-year-olds reached record highs in 2022, affecting 1 in 31 children.

The U.S. National Institutes of Health has announced awards totaling more than $50 million for research into potential causes of autism spectrum disorder and the effectiveness of current treatments. Here is what you need to know.

HOW IS AUTISM DIAGNOSED?

Autism is a neurological and developmental condition marked by disruptions in brain-signaling that cause people to behave, communicate, interact, and learn in atypical ways.

There are no objective tools for diagnosing Autism Spectrum Disorder, the medical name for autism, such as blood tests or brain scans. Instead, diagnoses are made based on observations and interviews.

The term spectrum reflects the wide range of possible manifestations. Some people with ASD may have good conversation skills while others may be nonverbal. Some may be acutely sensitive to sounds, touch, or other triggers. Some may have restricted or repetitive behaviors or interests. Some may need help with daily living, while others require little or no support.

The American Academy of Pediatrics recommends screening all children for autism at 18 and 24 months, when most children will begin to show symptoms. Yet the average age of diagnosis remains close to 4 years in the U.S. and 5 years globally.

HOW COMMON IS AUTISM?

By 2022, the U.S. autism rate in 8-year-olds was 1 in 31, or 3.2%, up from 2.77% in 2020, 2.27% in 2018 and 0.66% in 2000, according to the U.S. Centers for Disease Control and Prevention. A 2021 study from England put the rate in children there at 1.76%, up from 1.57% in 2009.

The World Health Organization estimates the worldwide ASD prevalence in children at 1%, up from 0.62% in 2012, with the caveat that many countries lack the resources to identify cases and report them.

WHAT CAUSES AUTISM?

The causes of autism are unclear. There is widespread speculation among scientists that its neurological characteristics may develop in utero, when the fetal brain is being wired. Studies have linked autism to maternal factors during pregnancy, and some research suggests a link to birth complications and timing of labor onset.

Genetic factors account for about 80% of the risk for developing autism, research suggests. A growing area of investigation focuses on epigenetics - the interactions between genetic and environmental factors. One theory suggests that a woman's exposure to air pollution or harmful contaminants before or during pregnancy may trigger a genetic mutation leading to autism in her child.

Gene variations in some people with autism strengthen the evidence for a genetic component. Among the genetic disorders linked with higher risks for autism are Fragile X syndrome, tuberous sclerosis complex, Phelan-McDermid syndrome, and Prader-Willi syndrome.

Other potential risk factors may include very low birth weight, jaundice as a newborn, complications in utero or during birth, having an unhealthy assortment of organisms living in the intestines, immune system disorders, having a sibling with autism, as well as a parent's age or health conditions, such as obesity and diabetes.

U.S. Health Secretary Robert F. Kennedy Jr., President Donald Trump and other public figures have promoted a theory - contrary to scientific evidence - that childhood vaccines are a cause of autism. The idea stems from a since-debunked study from British researcher Andrew Wakefield in the late 1990s that connected a rise in autism diagnoses with widespread use of the measles vaccine.

No rigorous studies have found links between autism and vaccines or medications, or their components such as thimerosal or formaldehyde. Vaccination rates have declined as autism rates have climbed.

Trump has also linked autism to the taking of widely used pain medication Tylenol by women when pregnant, elevating claims not backed by scientific evidence. The World Health Organization, the American College of Obstetricians and Gynecologists, and other professional societies continue to advise that pregnant women can use Tylenol, also known as acetaminophen or paracetamol, as needed while pregnant under a doctor's supervision.

“The conditions people use acetaminophen to treat during pregnancy are far more dangerous than any theoretical risks and can create severe morbidity and mortality for the pregnant person and the fetus," ACOG said in a statement.

WHY ARE AUTISM RATES RISING?

Researchers largely attribute the rise in autism diagnoses to more widespread screening and the inclusion of a wider range of behaviors to describe the condition. Historically, the definition of autism included moderate to severe intellectual disabilities. Today doctors recognize that the most severe forms account for only about 25% of cases.

In 2013, mental health experts combined what had been three separate diagnoses - autistic disorder, Asperger’s disorder and pervasive developmental disorder - under the umbrella of autism spectrum disorder.

An October 2024 study of U.S. insurance claims data found the largest increases in diagnoses were in groups with low screening rates in the past, including young adults, females, and children from some racial or ethnic minority groups.

Researchers have also noted that certain possible risk factors have become more common, such as having been born prematurely or to older parents.

Diagnoses of more severe forms of the disorder, known as profound autism, have not risen as dramatically as rates of non-profound autism, the CDC has reported.

ARE THERE TREATMENTS?

There are no scientifically documented treatments or cures for autism, nor can it be reversed. However, experts agree that early diagnosis is crucial. Intervention with supportive measures – ideally before age three - is critical for improving cognitive, social and communication skills.

Such measures can include speech therapy, occupational therapy, social skills training, sensory integration therapy, visual aids, structured routines, individualized education plans, family therapy, and providing a calm and predictable environment.

The U.S. Food and Drug Administration recently announced approval of leucovorin, or folinic acid, which Trump and Kennedy have suggested as a treatment for autism symptoms.

The FDA cited a review of the use of leucovorin in 40 patients with a rare metabolic disorder called cerebral folate deficiency that can lead to a range of neurological symptoms, some of which are seen in people with autism.

The science regarding leucovorin and autism "is still in very early stages, and more studies are necessary before a definitive conclusion can be reached,” the Autism Science Foundation said in a statement.

The data in favor of treatment with leucovorin is “from four small randomized controlled trials, all using different doses and different outcomes, and in one case, reliant on a specific genetic variant,” the Foundation notes on its website.

(Reporting by Nancy Lapid; Editing by Bill Berkrot)