Executive functions and physical aggression after controlling for attention deficit hyperactivity disorder, general memory, and IQ

This study examined the role of ADHD in the association between physical aggression and two types of executive functions. Boys received a cognitive-neuropsychological test battery over the ages of 13, 14, and 15 years. Diagnostic Interview Schedule for Children (DISC 2.25) data were collected from the boys and one parent between ages 14 and 16, and an IQ estimate was obtained at age 15. Three groups, differing in stability and level of physical aggression since kindergarten, were formed: Stable Aggressive, Unstable Aggressive, and Non-aggressive. Composite scores of validated executive function tests of working memory representing subjective ordering and conditional association learning were formed. A MANCOVA (N = 149) using ADHD status, teacher-rated negative emotionality, general memory abilities, and IQ as covariates was performed on the two composite scores. ADHD and teacher-rated emotionality did not provide significant adjustment to the dependent variables. Number of ADHD symptoms was negatively associated only with general memory and IQ. General memory contributed significantly to adjusting for conditional association test scores. Group differences indicated lower conditional association scores for Unstable Aggressive boys relative to the other groups. Both IQ and general memory abilities interacted with subjective ordering within the groups. Specifically, Stable Aggressive boys performed poorly on this measure and did not benefit from increases in IQ whereas Nonaggressive boys performed best and were not disadvantaged by lower general memory abilities. This suggests a relationship exists between aspects of working memory and a history of physical aggression regardless of ADHD and IQ.