Reading difficulties and cognitive-neurophysiological impairments in ADHD
: a focus on development and aetiology

Student thesis: Doctoral ThesisDoctor of Philosophy


This thesis uses a multidisciplinary approach to examine attention-­‐deficit/hyperactivity disorder (ADHD) in the context of development and co-­‐occurring impairments. The first part of the thesis focuses on the co-­‐occurrence between ADHD and reading difficulties, investigating underlying cognitive impairments and their possible shared aetiology. We show, in a clinically ascertained sample, that the shared familial influences on ADHD and reading difficulties are largely independent of familial influences shared with IQ. Using a population-­‐based twin sample, we further show that a significant proportion of the shared genetic influences on inattention symptoms and reading difficulties are captured by the cognitive processes of reaction time variability (RTV) and verbal memory, although the majority of the genetic sharing remains unaccounted for. The second part of the thesis reports findings from a follow-­‐up study of ADHD and control sibling pairs. First, in an investigation of the neurophysiological basis of decreased attentional fluctuation, we show that a fast condition with rewards normalises attention allocation (early-­‐P3 amplitudes) and improves RTV in individuals with ADHD. Second, childhood measures of ADHD symptom severity, socio-­‐economic status, IQ and actigraph movement level predicted ADHD severity in adolescence and young adulthood, whereas other cognitive variables did not. Third, in an investigation of cognitive-­‐neurophysiological markers of ADHD persistence and remittance, the pattern of results was indicative of three processes underlying outcome in ADHD: i) markers of recovery (preparation-­‐attention-­‐vigilance measures); ii) executive control processes (inhibition and working memory) that were not significantly associated with ADHD outcome; and iii) IQ as a potential moderator of ADHD outcome: in addition to childhood IQ predicting future ADHD outcome, it was associated with ADHD symptom improvement at follow up. These findings emphasise the role of IQ in ADHD outcome, and the malleability of the preparation-­‐vigilance-­‐attention processes, which are candidate targets for future development of non-­‐pharmacological interventions.
Date of Award1 Feb 2014
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorGrainne McLoughlin (Supervisor), Jonna Kuntsi (Supervisor), Grainne McLoughlin (Supervisor) & Jonna Kuntsi (Supervisor)

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