Attention deficit hyperactivity disorder (ADHD) in adulthood is associated with impairment of multiple aspects of cognition which adversely affect the individual’s everyday functioning. However, little is known about how these impairments are intertwined. This study explores whether impairments in basic processes (processing speed and distractibility) in adults with ADHD explain impairments in higher order functions, namely executive functions, memory, and complex attention. Furthermore, it is explored whether pharmacological treatment with methylphenidate (MPH) affects basic processes and higher order functions. A between-subjects design compared patients with ADHD without stimulant drug treatment (N = 55) and patients with ADHD treated with MPH (N = 31) with a healthy control group (N = 80). A neuropsychological test battery assessing basic processes and higher order functions was administered. Hierarchical logistic regression analyses were performed to evaluate the contribution of basic processes to impairments in higher order functions. Patients with ADHD not treated with MPH showed impairments in basic processes and higher order functions compared to controls. The impairments in basic processes explained 41–43% of impairments in executive functions, 27–29% in memory, and 56–74% in complex attention. In patients with ADHD treated with MPH, basic processes were not impaired and did not contribute significantly to impairments of higher order functions. Basic processes may constitute part of the foundation of cognitive impairments in adult ADHD. MPH may improve cognitive performance, presumably through improving basic processes. Applying this information could optimize neuropsychological assessments and inform treatment strategies by targeting basic processes.

Background Many clinical studies reported deficits in basic and complex cognitive functions in adults with Attention-Deficit/Hyperactivity Disorder (ADHD). However, the extent in which deficits in basic functions (i.e., processing speed and distractibility) contribute to complex cognitive impairments (i.e., working memory, planning, cognitive flexibility, memory functions) in adults with ADHD is not well-studied. So far, literature show only one study, revealing that basic functions explain 27–74% of executive dysfunctions. Yet, the authors reported that findings could be affected by the selection of neuropsychological tests. The goal of the present research is to replicate such a finding using a different sample and a different set of neuropsychological tests. Methods Forty-eight adult patients with ADHD were compared with 48 healthy controls in basic cognitive functions, namely processing speed and distractibility and more complex cognitive functions, namely selective attention, cognitive flexibility, planning, working memory, verbal fluency, and verbal memory. Basic and complex cognitive functions were assessed using the Vigilance and Sustained Attention, Selective Attention, N-Back, Tower of London, Trail Making Test, Word Fluency, and Verbal Learning and Memory. Results and conclusion Logistic regression analyses showed that impairments in complex cognitive functions explained 25% of the variance in ADHD diagnosis. The explained variance dropped from 25% to 9% after considering basic functions of processing speed and distractibility. This 64% reduction highlights the importance of basic functions for impairments in complex functions in patients with ADHD.

Adults diagnosed with attention-deficit/hyperactivity disorder (ADHD) commonly experience impairments in multiple domains of daily living. Work has a central role in daily life and is susceptible to ADHD due to its cognitive demands. The present study seeks to examine the nature of work-related problems and impairments of adults with ADHD, and explores the association to ADHD symptoms and neuropsychological test performance. A community sample of 1231 individuals took part in this study and completed a set of questionnaires assessing ADHD symptoms and work-related problems. Furthermore, a clinical sample of 134 adults diagnosed with ADHD were recruited from an ADHD outpatient clinic, who completed the same set of questionnaires. A subsample of 51 patients with ADHD additionally performed a neuropsychological assessment using tests of attention and executive functions. Work-related problems were found both in individuals of the community sample with symptoms of ADHD and individuals diagnosed with ADHD. Individuals with ADHD reported work related problems particularly in not meeting their own standards and perceived potential, yet it less commonly manifests in negative performance evaluations at work or job loss. ADHD symptoms, in particular symptoms of inattention, were found to be strongly associated with work-related problems, whereas neuropsychological test performance was no meaningful predictor of functioning at work. This study emphasizes the susceptibility of individuals’ functioning at work to ADHD symptoms and impairments associated with ADHD. ADHD related difficulties at work should be considered in the clinical evaluation and targeted screening at the work place to provide support when indicated.

Although attention deficit hyperactivity disorder (ADHD) in adulthood is associated with marked cognitive impairment, research on metacognition in adult ADHD is scarce. Deficits in metacognition may have a negative impact on treatment adherence, functional outcomes, and everyday life. This study explores metacognition, specifically self-awareness of cognitive performance, in adults with ADHD by combining objective and subjective assessments. Forty-seven patients with ADHD and 47 control individuals completed a neuropsychological assessment battery including tests for attention, executive functions and memory (objective assessment), as well as questionnaires for cognitive functioning and symptom severity (subjective assessment; self- and informant-report). Participants evaluated their test performance of the objective assessment after test completion by selecting a percentile rank which was subtracted from their normed test result, yielding a discrepancy score. Compared to controls, adults with ADHD showed impairments in attention (medium effects) and memory (small and medium effects), but not in executive functions. The discrepancy scores between self-evaluation and cognitive performance revealed deficits in self-awareness of attentional functions (small effects), but not in executive functions and memory in patients with ADHD compared to controls. Discrepancy scores between self- and informant-reports of cognitive functioning revealed no significant differences. Adults with ADHD show impairments in metacognition in attentional functions, but may have intact metacognitive abilities in other domains. Patients with ADHD tend to overestimate their abilities, especially in attentional functions. Subjective and objective measures of metacognition may not correspond, highlighting the need for clinicians to not solely rely on patients’ self-report in their assessment.

The present study confirms the conclusion that self-reported impairments are susceptible to noncredible responses and should be used with caution in the clinical evaluation of adult ADHD.