Cognitive-neurophysiological markers of ADHD

: Developmental pathways and comparison with bipolar disorder

Abstract

Attention-deficit/hyperactivity disorder (ADHD) is a highly heritable neurodevelopmental disorder associated with wide-ranging impairments in cognitive and brain functions. This thesis uses a multi-disciplinary approach to study cognitive and neurophysiological impairments in ADHD in adolescence and adulthood. The first part of this thesis examines the developmental and aetiological pathways of cognitive and electrophysiological (EEG) measures in a follow-up sample of adolescents and young adults with a childhood diagnosis of ADHD, their siblings and age-matched controls. The findings suggest that cognitive and event-related potential (ERP) indices of attention-vigilance and error processing are markers of ADHD remission, distinguishing between individuals with persistent and remitted ADHD at follow-up. Instead, cognitive and ERP measures mapping onto executive and conflict-monitoring processes, and indices of brain functional connectivity during cognitive performance are insensitive to ADHD outcome, as they do not differentiate the remitted and persistent ADHD groups. By examining the aetiological structure of a broad range of cognitive and ERP measures sensitive to differences between individuals with persistent ADHD and controls, this thesis further shows that impairments in these measures map onto three partially separable aetiological processes, which show moderate-to-large overlap with the aetiological influences on ADHD. The second part of this thesis examines how cognitive-neurophysiological profiles differ between women with ADHD, women with bipolar disorder (BD) and control women, to identify impairments that are specific to or shared between ADHD and BD. The findings provide evidence for multiple commonalities in cognitive and EEG measures of attentional processes and inhibitory control. A few impairments distinguishing between the disorders also emerged, which, if replicated, may represent candidate biomarkers to help dissociate ADHD from BD. Overall, by using a combination of cognitive, neurophysiological, developmental and sibling-modelling approaches, this thesis furthers our understanding of the developmental and aetiological pathways to ADHD, and of the specificity of atypical cognitive and neural profiles in adolescents and adults with the disorder.

Date of Award	2017
Original language	English
Awarding Institution	King's College London
Supervisor	Jonna Kuntsi (Supervisor), Fruhling Rijsdijk (Supervisor) & Grainne McLoughlin (Supervisor)