A common factor for childhood syndromes and disorders : empirical evaluation and associated risk factors

There is strong evidence of excessive levels multivariate comorbidity for the major childhood internalizing and externalizing syndromes and / or disorders. The overall aim of this thesis is to propose a general factor to capture the common variance for the major internalising and externalising childhood syndromes and disorders. In this context, the thesis reports three empirical studies to evaluate the plausibility of a common factor, and potential risk factors that may be associated with it. Study 1, examined if childhood psychopathology could be characterised by a bifactor model, which would provide support for a common factor. The bifactor structure was tested on data from a clinical sample of 974 parents and their children referred to the Royal Children's Hospital, Melbourne. Data was gained from the Syndrome and DSM-Oriented scales of the Child Behavior Checklist (CBCL), and the Anxiety Disorders Interview Schedule for Children-Parent Version. The model was also tested on the data from the Achenbach System of Empirically Based Assessment (ASEBA) Reference Group; an epidemiological sample used to validate the CBCL. The bifactor model showed excellent fit and substantive support for the hypothesised common factor. Study 2 extended Study 1 and investigated whether the major childhood syndromes/disorders conform to a circumplex structure, which would provide support for the presence of a common factor underlying these syndromes/disorders. The circumplex was tested using the same data and same measures as Study 1, and results demonstrated that child psychopathology conforms to a circumplex structure, with more than fifty percent of all variance accounted for by the common factor. This provided strong support for the presence of the hypothesised common factor. Study 3 aimed to investigate the nature of this hypothesised common factor, and investigate which constructs are associated with it. The association of three constructs ‚Äö- negative affective temperament, parental psychopathology and familial functioning ‚Äö- on the general factor specified by the bifactor model was investigated. The results demonstrated that negative affect and parental psychopathology, both individually and in interaction, appear to be key risk factors associated with the common factor. Overall, results suggest that, in contrast to current conceptualisations of childhood psychopathology as discrete and distinguishable entities, there is a common liability to all psychopathology in childhood. Such a common liability helps explain the high level comorbidity of childhood disorders and syndromes, because the liability suggests that all manifestations of psychological illness may, at least in part, have some common geneses. The results here suggest that negative affect and parental psychopathology are key risk factors in understanding this common liability factor.