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Investigating the link between attention deficit/hyperactivity disorder and depression

Powell, Victoria Iris 2020. Investigating the link between attention deficit/hyperactivity disorder and depression. PhD Thesis, Cardiff University.
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There is increasing evidence of an association between attention deficit/hyperactivity disorder (ADHD) and depression, but potential mechanisms explaining this are unclear. The overall aim of this thesis was to expand the current literature by investigating different factors that might contribute to the association between ADHD and depression, and to examine the impact of ADHD on the clinical presentation of depression. First, the prospective association between childhood ADHD and adolescent depression was investigated and academic attainment and friendship difficulties were tested as mediators of this association. In a general population sample, ADHD at age 7 was associated with depression 10 years later. Part of this association was mediated by academic attainment and friendship difficulties. Second, friendships were examined in more detail by testing different features of friendship (presence of friends, quality of friendships and the characteristics of the friendship group) as mediators of the association between ADHD and depression. In addition, I tested whether parent-child relationship quality could mitigate against friendship difficulties. In a sample of secondary school pupils, friendship quality mediated part of the association between ADHD and depression 7 months later, and mother-child relationship warmth appeared to slightly mitigate against this mediation effect. Third, the genetic overlap of ADHD and major depressive disorder (MDD) was examined by identifying specific regions of the genome that might contribute to the genetic overlap. In a genome-wide association (GWA) study meta-analysis of ADHD and MDD, 14 shared genomic regions were identified, nine of which were not highlighted previously in individual ADHD or MDD GWA studies. Finally, the impact of ADHD on depression clinical presentation was investigated. In a prospective cohort of recurrently depressed adults, ADHD was associated with features of depression presentation, including an earlier age at onset and greater impairment, recurrence, odds of self-harm or suicide attempt and taking nonstandard depression medication.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Medicine
Date of First Compliant Deposit: 5 March 2021
Last Modified: 04 Mar 2022 02:30

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