What Causes Autism In Children? 6 Facts You Need to Know

Nancy Wiseman had a feeling early on that something was different about her daughter Sarah. When Sarah was 6 months old, she stopped babbling, and by 10 months, she was silent. By 18 months, the increasingly aloof toddler no longer responded to her name, and she resisted being held, kissed, or touched.

"I felt that I was losing my child a little more each day," says Wiseman, of Merrimac, Massachusetts. When Sarah wasn't saying any words or even making sounds that resembled words by 20 months, her grandmother, a school psychologist, suspected that she might actually be deaf. Instead, Wiseman learned that her daughter was autistic. "The diagnosis really knocked the wind out of me," she recalls, "but I was relieved to finally know."

There is a lot that isn't fully known about autism, but researchers do believe there is a genetic component. So, for example, if you have autism, it's more likely your child will be autistic too. Although the severity of autism can vary widely, many children with the neurological disorder—which typically appears in the first three years of life—have problems speaking, interacting with others, sharing affection, and learning like Sarah.

Thanks to the tireless efforts of parents and advocates, public awareness of autism spectrum disorder (ASD) has grown tremendously since it was first identified in 1943. Still, it is gaining even more attention today than ever before. Congress has held hearings on the condition. Public health agencies are spending millions to study it. Researchers at countless universities are racing to find the causes and best treatments.

"There are many unanswered questions," says Alice Kau, PhD, an autism expert at the National Institutes of Health, which funded more than $74 million in autism research in 2002, compared with only $22 million in 1997. Still, researchers are beginning to make progress in unraveling this baffling disorder.

Here are six facts about what causes autism in children that every parent should know—including what does not cause autism and how early intervention may be key.

Autism May Be Genetic

While scientists do not know what causes autism, there may be a genetic component. According to the U.S. Department of Health and Human Services, autism tends to run in families. What's more, evidence now suggests that mutations of certain genes can increase one's risk of being autistic. Still, it's important to note that this link is complex. "Most people with autism have different mutations and combinations of mutations," the study explains. "Not everyone with autism has changes in every gene that scientists have linked to ASD."

While researchers are still working to understand how genetics play a role in autism, there are currently no genetic tests that can be used to predict or diagnose autism in an individual.

Environmental Factors Can Play a Role

Many conditions can be caused by environmental factors, including autism. Some chemicals can (and do) increase your risk. Researchers have identified several chemicals that they believe may have a possible connection to the increased risk of developing ASD; these include:

• Air pollution
• Pesticides
• Bisphenol A
• Phthalates
• Mercury or lead

This same research noted that nutritional deficiencies in folic acid, vitamin D, and fatty acids might also play a role in the increased risk of developing ASD. That said, the researchers also noted that exposure to these and other chemicals and nutrient deficiencies alone are not enough to cause ASD and that more studies are warranted. For example, one area that researchers agree needs further exploration includes how socioeconomic factors may influence the risk of developing ASD.

Vaccines Have Not Been Linked to Autism

Even though there's been widespread controversy about a possible connection between vaccines and autism, according to the Centers for Disease Control and Prevention (CDC), vaccines do not cause autism. Some parents of children whose autistic symptoms first appeared shortly after their measles-mumps-rubella (MMR) immunization are convinced the shot was the cause, but repeated studies have failed to find scientific evidence.

What's more, the one small-scale—and heavily criticized—study that suggested otherwise has been retracted and debunked. In January 2011, the British Medical Journal publicly denounced Dr. Andrew Wakefield, the author of the study. They cited the research as "fraudulent," stating he had "falsified data" and tampered with his research results to give the MMR vaccine bad publicity.

"Any apparent association [between vaccines and autism] is a coincidence," says Neal Halsey, MD, director of the Institute for Vaccine Safety at Johns Hopkins University in Baltimore. Around a quarter of children with autism experience regression at 12 to 18 months. That is to say that they develop as expected but then suddenly lose communication and social skills. This onset of symptoms just happens to coincide with when the MMR vaccine is administered for these kids, as the first dose of the MMR vaccine is routinely given between 12 to 15 months.

The possibility that mercury poisoning might cause autism is also a concern. Since the 1930s, a preservative called thimerosal, which contains small amounts of mercury, had been used in some childhood vaccines (not MMR). Although mercury is known to be harmful to the brains of infants and young children, most vaccine experts say the amounts used in the preservative were too tiny to cause neurological damage. Nevertheless, manufacturers voluntarily began removing thimerosal in 1999, and by the end of 2001, none of the routine vaccines given in early childhood contained the preservative. The preservative is now used only in flu shots and some vaccines given to adults and adolescents.

Infections During Pregnancy Can Increase Your Child's Autism Risk

While vaccines haven't been linked to autism, exposure to infection in the womb seems to increase a child's risk. A study released in 2019 and published in JAMA Psychiatry analyzed 1,791,520 Swedish children. It found that if a pregnant person suffered from a severe infection, their child was 79% more likely to be diagnosed with ASD. The increase was found with both major infections (like sepsis, pneumonia, meningitis, and flu) and minor infections (like urinary tract infections). Dr. Kristina Adams Waldorf, the co-author of the study, said the results should encourage pregnant people to get the flu shot, which is safe for pregnancy and can prevent serious complications.

Other Biological Factors Can Contribute to Autism

In addition to genetic and environmental factors, certain biological components can increase one's risk of ASD. These include, but are not limited to:

• Problems with brain connections
• Problems with growth (or overgrowth) in certain areas of the brain
• Problems with metabolism
• Problems in the body's immune system, which protects against infections

Early Autism Treatment Is Crucial

There is no known cure for autism, but intensive therapy can help children learn a wide range of skills, from making eye contact to hugging to having a conversation. Because autistic children have very different behaviors and abilities, the most effective approach takes into account a child's unique challenges and encourages healthy development through play rather than just trying to change specific symptoms.

And the sooner a child begins, the better. A panel of experts convened by the National Academy of Sciences in 2001 recommended that children should have 25 hours of therapy per week as soon as autism is suspected.

"Intervention can take many forms, from going to a regular preschool to a parent's working with her child over the course of a normal day to direct therapies from well-trained teachers and professionals—all depending on the child," says Catherine Lord, PhD, director of the Center for Autism and Communication Disorders at the University of Michigan in Ann Arbor.

Thanks to early intervention, some children—like Nancy Wiseman's daughter, Sarah—make remarkable progress. "At the very least, we're able to lessen the severity of symptoms," says Dr. Lord. "The latest studies show that almost 80% of kids with autism now have some speech by age 9, whereas only 50% of these kids were talking 20 years ago."

And though past research suggests that most autistic children have below-average cognitive abilities, a recent study found that early treatment raised children's IQ scores by about 20 points to almost normal levels. Those who started therapy as toddlers were also more likely to attend regular kindergarten.