The relationship between normal variation in IQ and common childhood psychopathology: A clinical study

Abstract

The relationship between normal variation in IQ and common psychopathology was examined in a sample of 339 5- to 16-year-olds who were seen at a tertiary psychiatric clinic. The mean IQ was 9.6 points lower (95% CI 5.5 to 13.6 points lower) for conduct than for emotional disorders, with mixed disorders in between. For these common disorders, the mean IQ was 6.0 points lower (95% CI 1.6 to 10.3 points lower) for females than males. IQ variation in the normal range was inversely related to a dimensional measure of conduct problems - an association that was not attributable to social class or mediated by scholastic attainments. Other dimensional measures of psychopathology - covering emotional symptoms, developmental immaturity and relationship difficulties - were not significantly correlated with IQ. Limitations of the study are discussed in the paper.

Child psychopathology and lower cognitive ability: a general population twin study of the causes of association

“…The association between these two traits has been found to be stable over time [1][2][3] and has been reported in clinical samples 4,5 as well as in populationbased samples. 6,7 Two general population cohort studies independently found that lower childhood cognitive ability was associated with non-psychotic psychopathology in adulthood.…”

Critical Periods of Vulnerability for the Developing Nervous System: Evidence from Humans and Animal Models

“…There is increasing evidence linking aggressive and criminal behavior with decreased IQ (362,363) as well as with other deficits typical of exposure to neurotoxicants, such as impulsivity and poor executive control. In a study of aggressive and nonaggressive adolescent boys, the best predictor of aggressive behavior was deficits in executive function (364).…”

Cognitive Functioning in Children with Oppositional Defiant Disorder and Conduct Disorder

“…Paternite, Loney, and Roberts (1995) used a similar strategy to examine IQ performance in a pure ODD group. Of these 11 studies, 3 found IQ-CD links after controlling for ADHD problems (Fergusson et al, 1993;Goodman, 1995;Lynam et al, 1993). Two studies had mixed results Loeber et al, 1995); the remaining 6 found no evidence of IQ deficits in pure CD youth.…”

“…Ten studies that reported CD-IQ analyses attempted to control for comorbid ADHD symptoms using correlational techniques or by constructing groups of pure CD subjects to contrast with other groups (Anderson, Williams, McGee, & Silva, 1989;Fergusson, Horwood, & Lynskey, 1993;Frick et al, 1991;Goodman, 1995;Lahey et al, 1995;Loeber, Green, Keenan, & Lahey, 1995;Lynam, Moffitt, & Stouthamer-Loeber, 1993;Moffitt, 1990;Schachar & Tannock, 1995;Taylor, Chadwick, Heptinstall, & Danckaerts, 1996). Paternite, Loney, and Roberts (1995) used a similar strategy to examine IQ performance in a pure ODD group.…”