To advance our understanding of the association between maternal smoking during pregnancy and the development of ADHD in offspring, studies using a prospective and longitudinal design, beginning with the study of temperament during infancy are required. The aim of this thesis was to investigate domains of infant temperament that could be considered early precursors and correlates of ADHD and to examine the effect of prenatal smoke exposure on these domains. Attention together with motor activity and heart rate (HR), measured during cognitive and emotional challenge, were studied in a representative, community sample of 130 infants at 6 and 12 months. At 6 months infants exposed to prenatal smoke showed more sustained attention, increased motor activity and increased HR compared with non-exposed infants. However, at 12 months there was no evidence of an effect of prenatal smoke exposure on attention or motor activity but there was evidence of an effect on HR. Given the importance of understanding temperament in infants, we examined 50 infants in an intensive laboratory assessment, using measures of vagal tone (VT) as well as HR, to enhance our understanding of the relationship between temperament and physiology. Results supported the use of HR as an index of temperament and although VT results were ambiguous, the indication was that measures of VT reactivity may be useful in future research. Combining the novel and rigorous designs presented in this thesis to study the effects of prenatal smoke exposure on offspring development, beginning during the neonatal period and with several assessments during the first year of life, utilizing physiological measures in combination with parent reports and behavioural observations, both at home and in more intensive laboratory settings, will be an important task for the future to enhance our knowledge of potential pathways from prenatal smoke exposure to the development of behaviour disorders, such as ADHD.
Online Research @ Cardiff (http://orca.cf.ac.uk/54941/1/U585330.pdf)