In reviewing 30 years of studies on Attention Deficit Hyperactivity Disorder (ADHD), doctors at University of Massachusetts Medical School and Northeastern University found that medication aimed at reducing hyperactivity was effective in reducing aggression as well.
ADHD is described as a neuropsychiatric disorder that affects between 4 and 12 percent of the general population of 6-to-12-year-old children. While the presence of aggression is not required for the diagnosis of ADHD, aggression is frequently observed in children and adolescents with ADHD.
Aggression and ADHD
Aggression may be obvious, involving physical assaults or temper tantrums, or the behaviors may be covert ones, such as cheating, lying, vandalism or shoplifting. When aggressive behaviors are severe, the child may be given a joint diagnosis of ADHD and conduct disorder. Research reveals that children often have both disorders.
Children, especially boys, exhibiting both ADHD and aggressive conduct disorder appear to be at the highest risk for poor outcomes that continue into adulthood, including aggression, delinquency and substance abuse.
More than 200 carefully controlled studies of stimulant medication demonstrate that such medication has significant positive effects on the core symptoms of ADHD, reducing inattention, impulsivity and motor hyperactivity. Studies also show that children with both ADHD and aggression (oppositional defiant disorder or conduct disorder) do not differ from non-aggressive children in their response to stimulant medication.
Effect of medication on aggression
However, fewer studies have directly investigated the effects of this medication on the aggressive behaviors themselves. Given the importance of aggression in influencing the long-term outcomes for children with ADHD, doctors recently studied the effects of medication on aggression in children with ADHD. These doctors analyzed research from 1970 to 2001, identifying 28 studies examining the effect of stimulant medication on aggression in children with ADHD that met strict quality standards.
Ratings by clinicians, parents and teachers were used to study the effects of medication. An overall rating was the measure of improvement representing the average effects for all reporters in each study. The effects were also analyzed in terms of the children’s age, gender, drug type, drug dose and length of treatment.
A total of 683 children and adolescents were included in the 28 studies. Stimulant treatment significantly reduced aggression as reported by clinicians, teachers and parents. The efficacy of stimulant treatment on overt and covert aggression was statistically reliable. Within each drug type, dose had no significant relation to the size of the effect on aggression. Only length of treatment showed a small positive effect on the reduction in aggressive behaviors.
Significant treatment effects
The main finding from this analysis of previous studies is that stimulants have significant treatment effects on aggression-related behaviors that occur in children with ADHD, and that these are separate from the drugs’ effects on the core symptoms of ADHD. The overall effect size was moderate to large for both overt and covert aggression.
These effects are similar in size to the overall effects of these drugs on ADHD symptoms. Improvements in conduct were independent of the ADHD symptom severity and their improvement. These researchers did find, however, that children identified as having ADHD with conduct disorder may be more difficult to treat. Effects were smaller in this group, and these researchers suggest that when ADHD children are also diagnosed with conduct disorder, stimulant medication may be less effective for their overt aggressive behaviors.
No gender effects were apparent. Boys and girls responded equally well to medication. There were some effects for age; aggression in older children appeared to respond better to medication, but these researchers suggest this may be due to the fact that aggression was more prevalent in older students and therefore the treatment effect was larger in this group.
There are several limitations to this analysis. First, there were relatively few studies of stimulant effects on aggression in children with ADHD. Also, overt aggression appears to be more commonly assessed than covert forms. Of the 28 studies analyzed, only 7 addressed covert aggression.
In addition, it is possible that measures of improvement in aggression may have been influenced by improvements in the core symptoms of ADHD. However, at least for overt aggression, the findings were large and consistent that stimulants reduce aggressive behavior while improving symptoms of ADHD.
“Psychopharmacology and Aggression: A Meta-Analysis of Stimulant Effects on Overt/Covert Aggression-Related Behaviors in ADHD” Journal of the American Academy of Child and Adolescent Psychiatry Volume 41, Number 3, March 2002 Pp. 253-261
Published in ERN April 2002 Volume 15 Number 4