Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder associated with wide-spread impairments in behavioural, neurocognitive and biological functions. This thesis aimed to investigate neurobiological and genetic correlates, as well as informant source validity, of ADHD in adolescents and adults using a multi-disciplinary approach. In the first part of the thesis, the aim was to evaluate the validity of informant sources for ADHD by examining associations with cognitive-neurophysiological correlates and future adverse life outcomes using both clinical and epidemiological samples. The findings suggest that both parent- and self-report of ADHD in adolescence and young adulthood may provide some valuable insight into symptoms and impairments, but parent-reports may have higher construct and predictive validity in this age range. In the second part of the thesis, the aims were to further our understanding of different neurobiological and genetic risk factors associated with ADHD, using cognitive-neurophysiological, electrodermal and genetic methods, in both clinical and population samples. Firstly, genetic analyses showed that ADHD risk alleles considered ‘en masse’, using polygenic risk scores, predicted several frequently co-occurring traits and disorders. These findings suggest that common genetic variation underlying risk for ADHD also contributes to higher body mass index, neuroticism, anxiety and depressive disorders, substance use, risk-taking and lower general cognitive ability in the general population. Secondly, analyses using electrodermal data suggest that abnormal autonomic arousal in ADHD varies as a function of recording context rather than reflecting stable impairments in the disorder. Finally, results from a randomised cross-over trial show that electroencephalogram (EEG) brain measures of executive and sustained attention improved after a single session of high-intensity exercise, suggesting that high-intensity exercise interventions may be appropriate for improving inattentiveness. Overall, this thesis provides insights into the validity of source-informants of ADHD in adolescents and young adults, and the nature of cognitive-neurobiological and genetic correlates of ADHD.
Investigation of neurobiological-genetic correlates and source-informants of attention deficit hyperactivity disorder (ADHD) in adolescents and adults
Du Rietz, E. E. C. (Author). 1 Oct 2018
Student thesis: Doctoral Thesis › Doctor of Philosophy