Connie Anderson, Ph.D.
IAN Community Scientific Liaison
Kennedy Krieger Institute
Date Last Revised: February 13, 2012
Date Published: November 8, 2011
Information shared by families participating in the Simons Simplex Collection project helps researchers explore questions about aggression in children on the autism spectrum.
Aggressive behaviors in children with autism spectrum disorders (ASD) often cause a great deal of difficulty for families. Hitting, kicking, biting, throwing objects, and other behaviors common during a temper tantrum or meltdown can greatly increase parent stress.1 To make things worse, a vicious cycle can begin so that behavior problems increase stress and increased stress (together with fraying nerves and poorer parental responses to the behavior) result in even worse behavior problems.2
Disruptive behaviors also may interfere with interventions meant to help a child, and with a child’s ability to succeed at school. They may keep a child barred from a variety of community activities. (Children with aggressive behaviors may not be welcome in after-school, scouting, sports, or other programs.) Furthermore, fear of aggressive incidents may keep a family at home, increasing their sense of isolation and decreasing their quality of life.
However, little work had been done to study aggression in children with ASD. Now, a new study reveals that aggression is extremely common in children on the autism spectrum, but is not associated with the same factors usually linked to aggression in typical children.
Asking Questions About Autism and Aggression
Despite its importance in the lives of children with ASD and their families, aggression has rarely been investigated by autism researchers. That is why Drs. Stephen Kanne and Micah Mazurek of the Thompson Center for Autism and Neurodevelopmental Disorders at the University of Missouri recently set out to explore two vital questions:
- How often do children with autism spectrum disorders (ASD) exhibit aggressive behavior?
- What risk factors are associated with aggressive behavior in children with ASD?
Thanks to families that participated in the Simons Simplex Collection (SSC), providing information about their children’s development and behavior at 13 university-based autism centers across North America, Drs. Kanne and Mazurek had enough information to take an in-depth look at these questions in a way that had not been possible before.
Many studies have examined risk factors for aggression in children with no disabilities. Factors such as male gender, low IQ, low family income, low parental education, and harsh parenting techniques have all been associated with increased aggression or antisocial behavior in typical children.3,4,5,6 Most studies looking at aggression in people with ASD, on the other hand, have focused on just a few individual cases, not on risk factors for people with ASD as a group.
Drs. Kanne and Mazurek set out to change this, carefully evaluating aggressive behaviors in 1,380 children with ASD between the ages of 4 and 17.7 Because the children had participated in the Simons Simplex Collection, the researchers had a rich set of information to draw upon, including the results of gold-standard autism assessments such as the Autism Diagnostic Observation Schedule (ADOS) and the Autism Diagnostic Interview - Revised (ADI-R), the results of IQ tests, and measures of repetitive behaviors, receptive language, and emotional and behavioral functioning.
How Many Children With ASD Had Aggressive Behaviors?
Among the entire group of 1,380 children with ASD, the researchers found that 56% were engaging in aggressive behaviors towards caregivers, while a smaller number (32%) engaged in these behaviors towards non-caregivers. Similarly, 68% of the children had previously behaved aggressively towards caregivers and 49% towards non-caregivers. These are extremely high rates, especially when compared with those for people who have intellectual disability (ID) but not autism. Aggressive behavior has been documented in only 7-11% of these individuals.8,9
This study therefore provides solid evidence that aggressive behaviors are a major challenge for families of children with ASD.
What Risk Factors are Associated with Aggressive Behaviors For Children With ASD?
The researchers wondered whether the same factors that are associated with aggression in typical children also would be associated with aggression in children with ASD. To find out, they divided the children into two groups: 489 children who had definitely displayed physical aggression such as hitting and biting and 549 children who had never or very rarely displayed aggression. Children in the middle, who had displayed only mild aggression, were dropped from the analysis so that the two other groups would be very distinct from one another.
The researchers were surprised to find that many of the risk factors associated with aggressive behaviors in typical children don’t apply at all to children with ASD. For example, being male is usually associated with a much higher risk of aggressive behavior, but this isn’t the case among children with ASD. Girls and boys with ASD are equally likely to be aggressive. In the same way, lower parental education, lower IQ, and lower language or communication ability are not associated with risk of aggressive behavior in this group of children with ASD, although they are in typical children. The only factor that seems to work the same way for children with ASD as it does for typical children is age: in both groups, the younger the child, the more likely he or she is to be aggressive. The children with ASD who are most likely to have aggressive behaviors, when compared with other children on the spectrum, are those with the following characteristics:
- More repetitive behaviors, especially self-injurious or ritualistic behaviors, or extreme resistance to change
- More severe autistic social impairment
- A higher family income
The information available did not permit the researchers to explore when and why children with ASD have aggressive outbursts. Their results do seem to dovetail with those of other researchers, however. For example, in 2005, researchers at the University of Kansas compared aggressive behaviors in 23 children with autism and 23 typically developing children and found the motivations behind the behavior are very different for the two groups. Typical children use aggression to achieve social goals, such as getting attention or avoiding adults’ demands. Children with autism – especially boys – become aggressive when adults interfere with a repetitive behavior, when someone tries to take away an item they need to continue a repetitive routine, or when they are trying to escape uncomfortable sensory input.10 The new (and much larger) study has again identified a link between repetitive behaviors and aggression.
One result is especially perplexing, and the researchers don’t know what to make of it. They had expected that families with more resources would have more access to interventions, and that their children would have fewer behavior issues. Why would higher family income be associated with a higher risk of aggression in children with ASD? “It is possible,” they wrote, “that families with higher incomes are better able to access interventions that challenge (and may be frustrating for) their child with ASD, and in turn may create situations that produce aggressive behaviors.”7 Another possibility is that people at different income levels may be more or less likely to report aggression. Perhaps those in lower income brackets are more sensitive to potential criticism of their parenting and blame for their child’s aggressive behavior, while higher income people are more immune to societal blame and so more freely report aggression in their children. Further research will be needed to see if this unexpected result holds up over time and, if so, how to explain it.
Shedding Light on Aggression and ASDS to Help Families
This new study provides confirmation that aggression is a major issue for caregivers of children on the autism spectrum, validating the experience of many and laying the groundwork for future research. It underscores the need for interventions to address aggression in children with ASD, and to support families coping with it.
- Lecavalier, L., Leone, S., & Wiltz, J. (2006). The impact of behaviour problems on caregiver stress in young people with autism spectrum disorders. Journal of intellectual disability research: JIDR, 50(Pt 3), 172-183.
- Baker, B. L., McIntyre, L. L., Blacher, J., Crnic, K., Edelbrock, C., & Low, C. (2003). Pre-school children with and without developmental delay: Behaviour problems and parenting stress over time. Journal of intellectual disability research: JIDR, 47(Pt 4-5), 217-230.
- Campbell, S. B., Spieker, S., Vandergrift, N., Belsky, J., Burchinal, M., & NICHD Early Child Care Research Network. (2010). Predictors and sequelae of trajectories of physical aggression in school-age boys and girls. Development and psychopathology, 22(1), 133-150.
- Lahey, B. B., Waldman, I. D., & McBurnett, K. (1999). Annotation: The development of antisocial behavior: An integrative causal model. Journal of child psychology and psychiatry, and allied disciplines, 40(5), 669-682.
- NICHD Early Child Care Research Network. (2004). Trajectories of physical aggression from toddlerhood to middle childhood: Predictors, correlates, and outcomes. Monographs of the Society for Research in Child Development, 69(4), vii, 1-129.
- Tremblay, R. E., Nagin, D. S., Seguin, J. R., Zoccolillo, M., Zelazo, P. D., Boivin, M., et al. (2005). Physical aggression during early childhood: Trajectories and predictors. The Canadian child and adolescent psychiatry review = La revue canadienne de psychiatrie de l'enfant et de l'adolescent, 14(1), 3-9.
- Kanne, S. M., & Mazurek, M. O. (2011). Aggression in children and adolescents with ASD: Prevalence and risk factors. Journal of Autism and Developmental Disorders, 41(7), 926-937.
- Emerson, E., Kiernan, C., Alborz, A., Reeves, D., Mason, H., Swarbrick, R., et al. (2001). The prevalence of challenging behaviors: A total population study. Research in developmental disabilities, 22(1), 77-93.
- Holden, B., & Gitlesen, J. P. (2006). A total population study of challenging behaviour in the county of Hedmark, Norway: Prevalence, and risk markers. Research in developmental disabilities, 27(4), 456-465.
- Reese, R. M., Richman, D. M., Belmont, J. M., & Morse, P. (2005). Functional characteristics of disruptive behavior in developmentally disabled children with and without autism. Journal of Autism and Developmental Disorders, 35(4), 419-428.