The impact of ADHD symptoms on intelligence test achievement and speed of performance

There is evidence of an association between Attention Deficit Hyperactivity Disorder (ADHD) and impaired performance on neuropsychological tests. Nevertheless, there is a dearth of research on this topic, particularly among forensic populations where rates of ADHD are notably high. This study aims to investigate the effect of ADHD symptoms on speed and performance on a non-verbal intellectual test. Forty three Icelandic male prisoners were screened for childhood ADHD using the Wender Utah Rating Scale (WURS), and for adult ADHD using the DSM-IV checklist of symptoms. IQ was measured using the Ravens Standard Progressive Matrices (RSPM) total score, and test completion time was also recorded. Correlations were conducted on the measures and the effect sizes ranged between small (childhood ADHD with RSPM total score and completion time) to large (adult ADHD with childhood symptoms, RSPM total score and completion time). Multiple regression analysis indicated that intellectual performance was significantly negatively affected by fast test completion time (medium effect size), but even after controlling for this, performance was further impaired by adult ADHD symptoms (large effect size). The results indicate that ADHD symptoms in adulthood adversely affect intellectual test performance above the speed of performance alone. 2011 Elsevier Ltd. All rights reserved.