Discover SPARK

Understanding Aggressive Behavior in Autism

Marina Sarris

Date Revised: October 29, 2020

At 21, Jonny is a loving son, strong and handsome, says his proud mother, Jill Escher. He also has severe autism, which affects almost every aspect of his life. When he’s frustrated, anxious, or experiencing an emotion that he cannot control, he may bite, scratch, or hit his family or caregivers. Once he pushed his mother’s thumb back so far it touched her forearm. “When you have a child who’s aggressive, it’s absolutely life changing,” she says.

But his mother wants people to understand: none of this is Jonny’s fault. “I don’t think for one second he intends to hurt anybody. He is so sweet. I think that his brain simply lacks an off switch that would restore control,” she says of these rare episodes. The Eschers participate in SPARK, the largest study of autism, to help advance our understanding of the condition.

Aggression, such as hitting, biting, scratching, hair-pulling, or kicking another person, is relatively common in children on the autism spectrum. A study of children and teenagers with autism found that 68 percent had been aggressive to a caregiver, and 49 percent had been aggressive to someone else, at some point.1 More than half of the youth studied were currently having mild to severe aggressive behavior.

That study was co-authored by clinical psychologist Micah Mazurek, Ph.D., an associate professor at the University of Virginia, where she directs the Supporting Transformative Autism Research program. She discusses aggression in this recording of a SPARK webinar.

In the general population, young children often become less aggressive as they get older and learn better ways to express themselves. But for some with autism, aggression persists through the teen years into adulthood. One study found that 15 to 18 percent of adults who have autism and intellectual disability showed aggression.2 Another study of autistic adults found that 5 percent of women and 14 percent of men had aggressive behavior over time.3

Because of their age, size, and strength, teens and adults with aggressive behavior could injure their families or caregivers. As president of the National Council on Severe Autism, a nonprofit advocacy group, Escher hears from parents whose teenage or adult children have hurt them. “I hear from single mothers who are alone and taking care of their sons, who are sometimes 200 to 300 pounds. They [the mothers] get beat up on a regular basis. And they have nowhere to go.”

Along with the threat of physical injury, “aggression can contribute to high parental stress,” Mazurek says. “It can cause burn-out for teachers and direct care staff because it’s stressful and sometimes painful to deal with.” And aggression also harms the people who have this behavior by limiting their opportunities and activities, she says.

Those adults often find it hard to get or keep a job, socialize with others, participate in community activities, and find a place to live, Escher says.

What Do We Know About Aggression?

Due to limited research on the topic, scientists do not know why aggression is more common in autism than in the general population, or what causes some people with autism to be aggressive while many others are not.

Aggression in people who have autism differs in some ways from aggressive behavior in other people. Males tend to be more aggressive in the general population, but aggression is equally common in males and females who have autism, Mazurek says.

Learning and language problems have been associated with aggression in the general population. But those links to aggression do not seem to be as strong in people with autism, Mazurek says. “There have not been many large scale studies on the topic of aggression in the autism population, but in the ones that have been conducted, language and IQ have not been significant predictors,” she says.

So what factors have been linked to aggression in people with autism? According to Mazurek and some studies,4,5 those factors include:

  • Significant repetitive behaviors
  • Self-injury (hitting or injuring oneself)
  • Sensory problems
  • Sleep problems, such as insomnia
  • Being younger in age.

The Problem of Sleep

Anna, a SPARK participant, says that her 7-year-old son with autism has a sleep disorder – and a problem with aggression, property destruction, and self-injury.

Her son, Zach, is a good student who speaks fluently. But when angry, he has hit his family members, thrown things at people, and banged his own head. Zach shares a bedroom with his brother, and one time his mother had to separate the boys because she was concerned Zach would hurt his brother. “Anybody being in that space, when he’s angry, is at risk of being hurt,” she says.

His sleep disorder causes him to awaken during the night – which can increase someone’s risk for aggressive behavior. Children who have autism are two to three times more likely to have insomnia than their typically-developing classmates, according to research.6,7

“When children with autism are not sleeping well, or if they’re waking up a lot at night, they may be more likely to engage in aggression and other challenging behaviors,” Mazurek says.

Another factor that has been linked to aggression happens to be one of the core symptoms of autism: repetitive behaviors. These behaviors may include hand-flapping, rocking, lining up toys, engaging in rituals, and insisting things stay the same, for example.

Children who have autism and more intense repetitive behaviors have a greater risk of aggression, Mazurek says. Studies have found that some children may become aggressive if someone interrupts their rituals or repetitive behaviors. Other studies have found a connection between sensory problems and aggression in children.

In a 2019 study, researchers placed youth with autism into different groups based on certain behaviors and characteristics. The two groups with the most aggression also had more anxiety and attention problems.8

More research is needed to better understand aggression in people who have autism, Mazurek says.

Reducing Aggression in Autism

Behavioral therapies and certain medications may help reduce aggression, Mazurek says. In behavioral therapy, a behavior analyst determines the purpose of the aggression and uses that information to develop ways to prevent it. The therapist also teaches the person new skills and behaviors to replace the aggression.

Two antipsychotic medications have been approved for the treatment of “irritability” in autism, which can include aggression and other behaviors. Some studies have found that a combination of medication and behavioral intervention may be most effective for some children.

Anna says that a blood pressure medication has helped reduce her son’s aggression and head-banging. He also switched to a smaller-sized class to reduce the stress of being in large and noisy groups at school. Many people with autism are sensitive to noises, lights, touch, or other sensory experiences.

Jill Escher says that behavioral therapies did not work for Jonny, who has intellectual disability and does not speak. But some medications have been helpful, including ones for his insomnia. She also tries to make sure that his environment is as stress-free as possible, and that his favorite music is playing in the background.

Escher points out that people who have severe autism may not be aggressive at all. In fact, she has a teenage daughter who has severe autism and an easy-going personality. Escher can take Sophie anywhere without fear, or the need for support staff.

Jill Escher worries about what will happen to people like Jonny as they, and their parents, get older. Where will they live? “The community placement system is not equipped to deal with severe behavior,” she says. “So people are caught in this nether world where there’s nowhere for them to go. There are very few programs for them, and parents are only a temporary set of supports. It’s an overwhelmingly serious crisis across the country and one that we have yet to grapple with in any meaningful way.”



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