Recent research has begun to acknowledge that parents of school-aged children with intellectual and developmental disabilities experience both positive and negative impacts when raising their children. Since some parents report feelings of a positive and a negative nature concurrently, within families research must attempt to discover the psychological variables that foster adaptation. This thesis aimed to extend current research in three ways. First parental cognitive variables and their incorporation into existing models of adaptation were critically discussed (Chapter 2). Second, relatively unstudied psychological variables were investigated with respect to both positive and negative parental adjustment. Third, longitudinal methodologies were used to draw conclusions as to the causal directions of the relationships and to ascertain whether the psychological variables acted as moderators or mediators i.e. were state- or trait-like.