Do low-effort learning strategies mediate impaired memory in ADHD?

As a group, participants with attention-deficit/hyperactivity disorder (ADHD) are impaired in academic performance and learning. This may be due to a mild intellectual impairment, impaired attention, or inability to allocate sufficient effort. If the latter is the case, this should be evident in the learning strategies applied. Four indices of learning strategy, considered to measure degree of effort, were analyzed from 67 participants with ADHD and 67 age-matched normal controls between 9 and 16 years of age. The participants with ADHD were impaired with regard to semantic clustering, retroactive interference, and percentage items reported from the middle section of the list even when controlling for IQ and comorbid conduct or oppositional defiant disorders symptoms. In addition, participants with combined ADHD (ADHD-C) did not display the normal proactive interference effect. The four effort indices explained 39% and 35% of the variance in free recall among participants with inattentive ADHD (ADHD-I) and ADHD-C, respectively. IQ was still significant when the effect of strategy measures were accounted for, whereas diagnosis was no longer significant when entered into the regression analysis after the effort indices. The study shows that participants with ADHD employ less effortful learning strategies than healthy controls and that low effort to a large degree can account for diagnosis related variance in memory performance.