Attention deficit hyperactivity disorder (ADHD) is a common and impairing neurodevelopmental disorder, which frequently co-occurs with autism spectrum disorder (ASD). Both disorders are highly heritable and recent studies report a substantial degree of overlap in genetic risks for ADHD and ASD. The overall objective of this thesis is to examine the clinical co-occurrence and shared genetic susceptibility of these conditions, as well as of related developmental problems. First, the presentation of ASD traits is examined in a clinical sample of children diagnosed with ADHD. This is followed by an assessment of whether the presence of ASD traits in children with ADHD is associated with additional cognitive or developmental difficulties. Lastly, it is investigated whether common genetic risk variants which are associated with clinically-diagnosed ADHD are also associated with ADHD traits, ASD-like social-communication difficulties and neurocognitive abilities (i.e. IQ, working memory, inhibitory control and facial emotion recognition) in children from a general population sample. The results show that ASD traits split into separate, albeit correlated dimensions of social-communication difficulties and restrictive, repetitive behaviours (RRBs) in children with ADHD. They also suggest that there may be some overlap of RRBs and hyperactive-impulsive ADHD symptoms. Increasing levels of ASD traits in children with ADHD are found to index more ADHD symptoms, as well as lower cognitive abilities and a greater likelihood of developmental difficulties. Finally, the results demonstrate that common genetic risk variants relevant to ADHD diagnosis are associated with ADHD and social-communication problems as well as cognitive difficulties (lower IQ and working memory abilities) in children in the general population. This thesis extends our understanding of the clinical importance of assessing ASD in the context of ADHD. Furthermore, the findings demonstrate that common genetic risk variants for childhood ADHD are also relevant to other neurodevelopmental and cognitive outcomes in the general population.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:633577 |
| Date | January 2014 |
| Creators | Martin, Joanna |
| Publisher | Cardiff University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://orca.cf.ac.uk/69188/ |
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