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An Investigation of Cognitive-Electrophysiological Biomarkers and Symptom Profile In ADHD and Bipolar Disorder.

Student thesis: Doctoral ThesisDoctor of Philosophy

The first part of this thesis aimed to examine the stability and validity of potential cognitive- electrophysiological biomarkers in Attention-Deficit/Hyperactivity Disorder (ADHD) in a large sample of adolescents and young adults. In part two, this thesis proceeded to a cross-disorder comparison with Bipolar Disorder (BD) in a novel sample of adult women, beginning by investigating symptom overlap between the two disorders and testing the efficacy of standard clinical instruments to delineate ADHD from euthymic BD. The next two chapters then went on to investigate the ability of cognitive-electrophysiological markers to delineate ADHD from BD in this cross-disorder sample, both through re-examining event-related potential (ERP) components which were investigated in part one, and by exploring additional ERP components. Presented herein are data which demonstrate that ADHD-control differences are sensitive to differences in experimental context, such as recording duration, as well as sample characteristics and certain methodological factors such as electrode selection. This research identified possible candidate biomarkers for both ADHD and BD; including two disorder-specific cognitive-electrophysiological markers which dissociated ADHD from BD. A further comparison of symptoms of inattention, hyperactivity, mania, depression and emotional lability (EL) in ADHD and BD using typical diagnostic measures indicated that depression, mania and EL measures were not able to distinguish ADHD from euthymic BD. Conversely, ADHD measures had good discrimination potential, and may currently be the best available method of delineating ADHD from BD in clinical contexts. This thesis recommended further research to confirm if the potential cognitive-electrophysiological biomarkers highlighted here are reliable indicators for either ADHD or BD. Further work is also needed to clarify the effects of methodological and samples differences on reported findings in these disorders across lifespan.
Original languageEnglish
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Award date2018

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