Differences in verbal and performance IQ in conduct disorder: Research findings from a Greek sample

Background: Conduct disorder reflects a persistent and repetitive pattern of antisocial behavior of children and adolescents and is among the most frequent factors for referral to child-psychiatric services. According to the existing literature, conduct disorder is associated with lower IQ, mainly verbal intelligence, in relation to the general sameage population. Objective: This study aimed to examine the differences in verbal and performance intelligence, on children and adolescents with and without conduct disorder in a Greek sample. Methods: The sample consisted of 121 Greek children and adolescents. Seventy-nine (65.3%) of the participants were girls and 42 (34.7%) were boys, age range between 9 and 17 years (Mean=13.43, SD=2.63). Fifty-five (45.5%) of the participants had a diagnosis of conduct disorder and 61 (54.5%) were healthy (control group). Conduct disorder diagnosis was made using the Kiddie Schedule for Affective Disorders and Schizophrenia for School-Age Children- Present and Lifetime version (K-SADS-PL), while Intelligence (IQ) was estimated using the vocabulary and block design subscales of the Wechsler Intelligence Scale for Children-IV. Results: For the whole sample, IQ scores (verbal IQ, performance IQ and total IQ) ranged within the normal values. No statistically significant differences on IQ scores were found based on participants' gender and age. Participants with conduct disorder showed significantly lower scores on the performance and total IQ in relation to the scores of the participants of the control group. Conclusion: This study highlights the correlation between CD and cognitive abilities, especially low IQ, something that has not been given much attention so far.