Primary and Secondary Features in Adults with Attention Deficit Hyperactivity Disorder and Autism Spectrum Disorder.

  • Ashley Stark

Student thesis: Doctoral Thesis


Attention-Deficit Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD) are considered to be diagnostically distinct disorders with notably divergent primary symptomatology (e.g., repetitive behaviour in ASD vs. inattentive behaviour in ADHD). However, individuals with these disorders often exhibit evidence of secondary or associated features that, whilst not diagnostically required, commonly occur across both groups (e.g., heightened levels of anxiety). Research exploring the primary and secondary features of ADHD and ASD has largely been drawn from clinical samples of individuals in the earlier stages of life (i.e., children and adolescents). Moreover, research on the primary and secondary features of ADHD and ASD has largely focused only on one disorder, with few studies actively conducting a comparative evaluation of the specific aspects of these disorders. To address the paucity of literature on community-based samples of adults with ADHD and ASD, the present research aimed to compare and contrast the features that present secondary to the primary diagnostic properties of these disorders, including cognitive, behaviour, and emotion-based features commonly observed in ADHD and ASD. Moreover, to investigate how both the secondary features of ADHD and ASD influence, and potentially heighten, the presentation of both other secondary and primary features of these disorders, this research aimed to explore the unique relationships between the primary and secondary features common to both disorders. A total of 278 adults participated in the two studies which comprised this research (90 diagnosed with ASD, 96 diagnosed with ADHD, and 92 neurotypical controls) with 107 identifying as male and 169 as female. Participants completed a series of self-report surveys assessing primary (i.e., core sympyomatology) and secondary features (i.e., executive functioning, inhibitory control, alexithymia, aggression, anxiety, and depression) of ADHD and ASD. In the first study, comparative analyses were conducted to assess whether differences existed with respect to the secondary features exhibited by adults with ADHD and ASD, as well as between adults with either ADHD or ASD and neurotypical controls. In the second study, the secondary features assessed in study one were then included in separate path analyses for the adults with ADHD and ASD to explore the relationships between the primary and secondary features of these disorders. Results from the comparative analyses demonstrated that all secondary features assessed were significantly higher in adults with ADHD and ASD in comparison to neurotypical adults, but that no significant differences existed between the majority of these secondary features in adults with ADHD and ASD. Moreover, path analytic findings demonstrated that the distinct diagnostic behaviours of each disorder were impacted by the six secondary features examined in this study. These findings are important, as greater exploration of the commonalities and distinctions between ASD and ADHD will allow for the development of a more uniform clinical framework for understanding the overarching relationships between these psychopathologies. Moreover, increased knowledge of features that impact symptom presentation in ADHD and ASD may further inform approaches to treatment and the reduction of problematic behaviour (and subsequent functional impairment) in adults with these disorders.
Date of Award13 Oct 2019
Original languageEnglish

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