Abstract
Attention Deficit/Hyperactivity Disorder (ADHD) is characterised by pervasive and impairing symptoms of inattention, impulsiveness, and overactivity. Theoretical models of ADHD have hypothesised that these symptoms arise through disruptions to neural systems that mediate executive functioning, motivation (responses to reward or threat), and arousal. These systems are interconnected and overlap with the neural substrates involved in detecting and responding to emotionally salient stimuli. From this context an interest has emerged in understanding how the experience or recognition of emotion may be disrupted in ADHD. The aim of this thesis was to build upon previous work in developing this understanding. For this purpose, a sample of 43 children (8 girls) with ADHD and a sample of typically developing (TD) children matched on age and gender were recruited to participate in three studies. The first study examined if the ADHD group would recognise fewer emotional facial expressions than the TD group. Importantly, by including similarly difficult task conditions that did not require emotion processing, this study examined if difficulty recognising emotional facial expressions resulted from impairments recognising emotion or other cognitive deficits. Results indicated that the ADHD group was similar to the TD group at recognising the nonemotion stimuli but significantly worse at recognising emotional facial expressions. This clarifies that ADHD is associated with deficits in processing emotional facial expressions beyond the other difficulties associated with the disorder. The second study examined if the ADHD group differed from the TD group on measures of autonomic activity in response to films selected to elicit particular emotions of fear, happiness, and sadness. Results indicated that the ADHD group differed from the TD group on a measure of sympathetic response for the films evoking fear and happiness but not sadness. These differences were moderated by the severity of Oppositional Defiant Disorder (ODD) symptoms within both the TD group and ADHD group. The results suggest that ADHD is associated with abnormal emotional responses for fear and happiness but this does not necessarily extend to all types of emotional responses, or at least not sadness. The third study compared how the ADHD and TD groups responded to social inclusion and exclusion using a computer simulated ball-throwing game. Social functioning depends largely on emotion and is impaired in ADHD. Results indicated that compared to the TD group, children within the ADHD group had a smaller increase in parasympathetic activity during the inclusion condition and less withdrawal in parasympathetic activity during the exclusion condition. The ADHD group also had a greater change in sharing behaviour following the exclusion condition. These results, taken together with the results from the previous studies, indicate that ADHD is associated with abnormalities in both emotion recognition and emotion response for a range of stimuli, within both social and non-social contexts. This is discussed in the context of possible underlying neurobiological systems that mediate motivation, executive functioning and arousal.