About 10% of low-functioning children with autism may "bloom" and outgrow most of their severe disabilities by adolescence.

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A new study offers some good news for families with autism. Most children affected by the disorder do not have intellectual disabilities, the study finds, and even among the severely low-functioning, about 10% may improve dramatically over time, with some growing out of their diagnosis by their teens.

The study tracked nearly 7,000 autistic children born in California between 1992 and 2001. The group included most of the children who received an autism diagnosis in the state during that time period. The kids were followed from diagnosis to age 14 or the oldest age they had reached by the time the data collection was concluded.

The researchers found that 63% of the children did not have intellectual disabilities. Although autism is known to cause cognitive deficits in some children, it is also associated with certain enhanced intellectual abilities, and some affected children have extremely high IQs.

About one-third of the study group were considered low- to low/medium-functioning in terms of communication and social skills, meaning that they may have trouble talking, interacting with others or socializing and making friends with peers.

High-functioning kids with autism, meanwhile, can communicate effectively with others, maintain friendships and are willing to engage in social pursuits. While the highest-functioning children tended to show the most improvement over time in the California study, about 10% of those who started out in the low-functioning group also moved into the highest group by age 14.

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“The critical finding is that when you look at those children that this study refers to as ‘bloomers’ — the children who seemed very low-functioning at the beginning and then did extremely well — they [tend not to] have any intellectual disabilities,” says Rahil Briggs, assistant professor of pediatrics at Albert Einstein College of Medicine, who was not associated with the research. Low-functioning children without intellectual disabilities were twice as likely to “bloom” as those who had cognitive deficits.

Briggs adds that another “very key” factor is that the mothers of the kids who bloomed tended to be more educated and not minorities. This suggests that low-income immigrant or minority families may not be receiving the services and support for their children that educated, affluent parents are able to access more easily.

With developmental disorders, the earlier a child receives help, the more likely he or she is to overcome disabilities. Early intervention matters because the brain is remarkably vulnerable early in life, built to shape itself to the environment it initially faces. “The young brain is disproportionately receptive to input, whether positive or negative,” says Briggs. “That’s why young children can learn a second language easily and why early exposure to domestic violence and toxic stress are so incredibly damaging.”

If autistic children receive intervention before such coping mechanisms as repetitive behaviors and extreme social withdrawal are firmly entrenched, for example, their innate oversensitivity to their environment is far less likely to become or remain disabling, and their other abilities and gifts can flourish. If these children are reached early enough, “we can actually start to change brain functioning if we provide the right kind of repetitive and focused intervention,” Briggs says.

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The American Academy of Pediatrics currently recommends that doctors screen children for autism at their 18-month well-child visit. Briggs adds that parents must become aggressive champions for their children. “So much can depend on how good that parent is at advocating for the child,” says Briggs, noting that parents need to be aware not only of what services are available, but also which ones are best, which are not helpful and how to get the best care.

“That puts an incredible burden on parents,” she acknowledges. With the Centers for Disease Control and Prevention reporting last week that autism now affects 1 in 88 children, it is becoming a burden shared by more and more American families.

Briggs says that the findings in the new study reflect the types of developmental trajectories she sees in children in her practice as director of the Healthy Steps program at Montefiore Hospital in the Bronx, which helps disadvantaged families access numerous services, including autism therapies, through their pediatricians’ office visits.

She describes working with a 5-year-old autistic boy and his family. The family said he would come home from kindergarten crying, but they couldn’t figure out what was wrong. Finally, he described how he felt while he waited for his mother to pick him up in the school’s cafeteria: “There were so many echoes bouncing off the walls that it felt like people were having a party in my head and they wouldn’t turn down the music,” he said.

Identifying the problem led Briggs to enroll the boy in listening therapy, which helped him cope with his sensitivity to sounds. When such sensory issues, which are common in autism, can be mitigated, children become far less stressed and far better able to learn other skills like social interaction and communication.

Most children from disadvantaged backgrounds aren’t able to get these kinds of services, however. “If we still see these huge differences in children with autism based on socioeconomic factors, we clearly don’t have enough programs or haven’t made them available enough,” Briggs says.

The research was published in Pediatrics.

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Maia Szalavitz is a health writer for TIME.com. Find her on Twitter at @maiasz. You can also continue the discussion on TIME Healthland‘s Facebook page and on Twitter at @TIMEHealthland.