Grant: Doctoral Award - Frederick Banting and Charles Best Canada Graduate Scholarships

Common mental disorders in children and adults can be considered as externalizing (e.g., anti-social personality disorder and substance dependence) and internalizing disorders (e.g., depression and anxiety disorders). Substance dependence, an externalizing disorder, has many negative consequences for affected individuals and society as a whole. Thus, the ability to identify those at risk for developing substance use problems will help healthcare workers to provide earlier interventions. Biomarkers provide a closer link between the genetics underlying a disorder and the clinical presentation of the disorder. In this way a biomarker may help in identifying the genes involved in a disorder. A reduction in a brain wave measure, known as the P300, has been proposed as a biomarker for substance abuse and other externalizing disorders. In order to be considered useful as a biomarker, the phenomenon should be specific to the disorder. However, current evidence is unclear whether this P300 abnormality occurs exclusively in association with a risk for developing an externalizing disorder, such as substance abuse, independent of a risk for developing internalizing disorders such as depression. The proposed study will examine the extent to which the reduced P300 is specific to a risk for externalizing disorders in a sample of young adults. Brain waves will be recorded while participants complete a task known to elicit the P300. The association between the size of the P300 and personality traits characterized as internalizing or externalizing will be determined. It is predicted that reduced P300 is specific to externalizing disorders so will be associated with externalizing rather than internalizing traits. Ultimately, the proposed research will help to not only identify the genes involved in externalizing disorders, but also to identify those at risk for developing these disorders, thereby, improving healthcare delivery by allowing for earlier intervention.