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Title: The identification of precursors in the early development of attention deficit hyperactivity disorder
Author: Meeuwsen, Mirjam
ISNI:       0000 0004 5351 7572
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2015
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The principal aim of this thesis was to identify precursors to symptoms of ADHD in early childhood in the context of a longitudinal study of first-born children (the Cardiff Child Development Study; CCDS). Three criteria were used to determine whether an early behaviour could be identified as a precursor. Firstly, the precursors should ‘resemble the later developmental outcome’. In line with features of the disorder, informant-reported and measured high activity levels during a number of tasks (reflecting inattention and impulsivity domains) in infancy were proposed as precursors of ADHD symptoms. Secondly, precursors needed to be associated with ‘well-established risk factors for the later outcome’. Associations with familial symptoms of ADHD and perinatal risk factors were therefore explored. Parental ADHD symptoms predicted ADHD symptoms and executive task performance at 33 months and 7 years of age, but were only related to increased activity levels during a restraint condition at 6 months. Perinatal risk factors predicted toddlers and childrens’ ADHD symptoms, but this was no longer significant when ODD symptoms were taken into account. Higher informant-reported activity levels at 6 months were associated with stress and smoking in late pregnancy, but measured activity levels were not related to perinatal risk. Thirdly, the precursors should show ‘continuity over time’. The relationships with later ADHD symptoms and executive functioning outcomes, measured in toddlerhood and then again at age 7 were therefore explored. Continuity over time was established for informant-reported activity levels at 6 months of age, which predicted later ADHD symptoms, even when ODD symptoms were controlled for. Infants’ measured activity levels did not predict measured activity levels in toddlers, symptoms of ADHD or executive functioning. The outcomes were more stable, with toddlers' ADHD symptoms and executive functioning significantly predicting outcomes in middle childhood. Two additional tests were performed. The first required that the precursor added predictive power, beyond the effects of the risk factors. Only informant-reported activity levels passed this test. The second test established whether risk factors were associated with consolidation of precursor states into later symptoms of ADHD (measured using standardised change scores). Risk factors were significantly related to a move from activity levels in infancy (informant-reported and measured) to later symptoms of ADHD. This thesis contributed to the literature by highlighting the need for clear criteria and a more consistent use of the term 'precursor'. A method for identifying precursors to ADHD symptoms in infancy was demonstrated, and showed that informant-reported (but not measured) activity levels were supported by all criteria and additional tests; except association with familial ADHD symptoms. This method for identifying precursors facilitates further prospective studies of etiological mechanism and could also inform the development of targeted prevention or intervention programmes.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: BF Psychology