Do Aggressive Behaviors Accumulate or Exchange over Time?

Background:  Aggressive behaviors, directed either toward the self or others, can cause severe psychological and physical damage to individuals with autism, their family, or others. Prior research on other common behaviors seen in individuals with ASD, such as restricted and repetitive behaviors, has shown that there are fluctuations in their prevalence over time (Richler et al., 2010). Previous research from this lab has noted that individual aggressive behaviors vary in their age of emergence, with self-injurious behaviors typically starting first, followed by aggression toward individuals in the family, and later by aggression toward others. No study has yet looked at fluctuations in aggressive behavior to see if children acquire a repertoire of several of these behaviors over time or switch from one aggressive behavior to another.

Objectives:  We hypothesized that children will acquire several behaviors as they age, starting with self-injurious behaviors, followed by aggression towards family, and ending with aggression towards others.

Methods:  A sample of 168 children (79% male) aged 2-22 years (mean=7.6, SD=4.16) were included in the analysis. Diagnosis of ASD was confirmed by both the Autism Diagnostic Interview, Revised (ADI-R) and the Autism Diagnostic Observation Schedule (ADOS). The Behavior and Sensory Interest Questionnaire (BSIQ, Hanson et al, 2015) was administered to parents to understand the time of emergence and cessation of autism related behaviors, including aggression. Children who exhibited at least two different aggressive behaviors were included in the analysis. Descriptive statistics were used to determine the relationship between the age of emergence and age of cessation of different aggressive behaviors. Percentages were calculated to determine how many of the behaviors that emerged later emerged prior to cessation of earlier behaviors.

Results:  Descriptive statistics reveal that 23.57% of later behaviors emerge at or after the cessation of the initial aggressive behavior. Additionally in a population of children that acquire two or more aggressive behaviors, the earliest form of aggression is typically aggression towards family members (onset of 3 years, 2 months on average), followed by aggression towards people outside of the family (3 years, 6 months on average) and finally self-injurious behavior (3 years, 10 months on average).

Conclusions:  Results regarding accumulation of aggressive behaviors over time are consistent with the initial hypothesis. The low percentage of children that switch from behavior to behavior indicate that children with ASD more frequently tend to build a repertoire of different aggressive behaviors, rather than switching between them. Contrary to the initial hypothesis, aggression towards caregivers and aggression towards people outside of the family tend to emerge earlier than self-injurious behavior in a sample of ASD children that have at least two aggressive behaviors. These results highlight the importance of intervention for children with ASD who develop aggressive behaviors prior to them building a larger repertoire.