Bullying can lead to depression, low grades, behavioral problems and even physical illness because of the stress it causes — and kids with autism may be suffering the brunt of the harm

A new study finds that children with autism spectrum disorders are bullied far more often than their typically developing peers — nearly five times as often — but parents of autistic kids think the rate is even higher than that.

In the study, about 46% of autistic children in middle and high school told their parents they were victimized at school within the previous year, compared with just over 10% of children in the general population. Calling it a “profound public health problem,” lead author Paul Sterzing of Washington University in St. Louis told the New York Times that the “rate of bullying and victimization among these adolescents is alarmingly high.”

Many people with autism have trouble recognizing social cues, which makes them awkward around others. They also often engage in repetitive behaviors and tend to be hypersensitive to environmental stimuli, all of which makes kids with the disorder ripe targets for bullies who home in on difference and enjoy aggravating their victims. About a third of autism cases are severely disabling — those affected may suffer from low IQ and be unable to talk — but most autistic people have average or high intelligence and many can function well, if their social and sensory issues are appropriately addressed.

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That may help explain why the highest functioning children in the current study were at greatest risk of being bullied. While their social awkwardness was more obvious because they actually interacted more with mainstream peers, this made their actual disability less visible, likely making their condition harder for their peers to understand.

Children with autism who could speak well, for example, were three times more likely to be bullied than those whose conversational ability was limited or absent. Further, those who were mainly educated in mainstream classrooms were almost three times more likely to be bullied than those who spent most of their time in special education.

The research, published in the Archives of Pediatric and Adolescent Medicine, involved survey data from 920 parents of autistic children, who were asked about their children’s experience of bullying.

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About 15% of autistic children were reported to be bullies themselves — roughly the same rate as in the general teen population — and 9% were both bullies and victims. Bullying, which can take the form of teasing, exclusion, humiliation or physical assault, can lead to depression and other mental health problems, along with poor grades and even physical illness in victims because of the severe stress it causes.

Parents of autistic children think that the true rates of victimization are far higher than what the study found, and that the rates of perpetrating bullying are lower, precisely because autism disorders are characterized by an inability to read subtle social cues and by difficulty with communication. In order to report being bullied, you need to understand when you’re being targeted, for example; in contrast, you also need to understand and effectively deploy harassing social information in order to be a bully — things that autistic children generally cannot do.

“The only thing I can figure out is that maybe the parents are misinterpreting their children’s clumsy attempts [to socialize],” says Eileen Riley-Hall, a high-school teacher with an autistic daughter and author of Parenting Girls on the Autism Spectrum: Overcoming the Challenges and Celebrating the Gifts, regarding the rate of bullies among autistic kids in the new study. “I think of bullying as systematic manipulation. But [autistic children] are so candid, they’re typically not capable of that kind of forethought and malice.”

Impaired language skills and inability to read social cues also mean that many autistic children are bullied without ever realizing it or being able to report it. Riley-Hall recalled an incident involving her daughter in elementary school. “Little boys were getting her to say dirty words and laughing at her. She thought this was a good thing and that they were being friendly, but they were really making fun of her,” she says, describing how another girl, who knew it was wrong, told the teacher. But until the classmate reported it, Riley-Hall had no idea that her daughter was being bullied.

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With recent national focus on the toll of school bullying, including bullying-related suicide, many school districts are updating their anti-bullying policies and states are giving the issue renewed legislative attention. Research finds that the best anti-bullying programs are comprehensive, involving the entire school and not just individual students. Programs that work well tend to encourage a warm school environment in which diversity is celebrated; they also rely on adults at the school, from the principal to the lunch ladies, to set a tone that clearly indicates that bullying isn’t acceptable. Studies find that students in schools that create such a welcoming atmosphere not only perform better academically, but also have lower rates of behavior problems like alcohol and drug use.

But despite efforts to encourage inclusion, acceptance of students with disabilities remains low overall. “There’s still a sense that they are not as fully human as other people,” says Riley-Hall.

Another factor that often leads to exclusion and derision is fear. “We have many generations who have had no personal experience with people with special needs, and they fear them,” Riley-Hall notes. “They pass that ignorance on to their children.”

As the study’s authors conclude: “Inclusive classrooms need to increase the social integration of adolescents [with autism] into protective peer groups while also enhancing the empathy and social skills of typically developing students towards their peers with [autism] and other developmental disabilities.”

Indeed, although autistic people are often claimed to lack empathy, their problems usually relate to an inability to understand the minds of others— not an actual lack of care when they know someone is suffering. Meanwhile, people without autism aren’t supposed to be impaired in understanding others’ pain, so what’s our excuse?

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Maia Szalavitz is a health writer at 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.