Working memory and executive functioning in adults with attention-deficit hyperactivity disorder without comorbidity

The present study addressed verbal and nonverbal working memory (VWM and NVWM) in 23 adults with ADHD and 21 controls, matched for age and years of education. This study avoided several of the usual confounds in the ADHD literature: employing an adult sample only; avoiding conditions comorbid with ADHD; screening out active mood and substance use disorders; assessing anxiety, phonological processing deficit, general verbal-cognitive functioning, ethnicity, gender, and central nervous system dysfunction.; Principle measures were well-normed psychometric tests with established reliability and validity (e.g., selected subtests of the Wechsler Adult Intelligence Scale, Third Edition). Interrelationships among both types of working memory and measures of attention control and inhibition were examined.; As predicted, the adult ADHD group, despite having general verbal cognitive functioning similar to the control group, performed significantly more poorly on both verbal and nonverbal working memory, and had larger discrepancy scores favoring general verbal cognitive functioning over verbal working memory, a pattern found to be highly pathognomic.; The notion that both VWM and NVWM tap a unitary construct separable from other factors in executive functioning, such as inhibition, was also tested. As predicted, all VWM measures loaded primarily on the first component of a factor analysis, together with NVWM. The variability scale of the Conners' Continuous Performance Scale, 2nd Edition, which measured attention control and distractibility, also showed a strong primary loading on the first component, a clustering that was interpreted as reflecting maintenance of effort.