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UBC Theses and Dissertations

Cannabis and aggression : differentiating reactive and instrumental aggression Carroll, Christopher Ryan


My thesis explored the relation between cannabis use (CU) and two distinct subtypes of aggression. Substantial prior research has examined the association between CU and aggression; however, empirical evidence has not yet provided a clear or complete picture of this relationship. This may be due to the fact that to date no studies have considered the important distinction between instrumental aggression (IA) and reactive aggression (RA). The aim of this study was to differentiate these subtypes of aggression while controlling for covariates such as psychopathy and trait aggression which has the potential to reconcile the apparently contradictory findings in the literature. Also of interest was the role that gender plays in the relationship between cannabis and IA/RA. Samples from three different populations, who all completed a series of self-report questionnaires, were examined for this study. The sample from the university population consisted of 427 participants, the sample from the online population consisted of 434 participants, and the sample from the treatment population consisted of 68 participants. The data were analysed using independent samples t tests, hierarchical multiple regressions, and two-way ANOVAs. The results from all three samples indicated that there is little to no relation between CU and IA/RA. In cases where a relation was found, it disappeared when accounting for psychopathy and trait aggression. These findings were consistent across all frequencies of CU. Furthermore, the results showed that there was no interaction between gender and any frequency of CU when looking at the relation with IA/RA. Collectively, these findings indicate that CU is not associated with aggressive behaviour and propose answers to the question of why there is such differing findings in the existing literature. The public health impact of CU remains controversial and these findings have important theoretical, methodological, and clinical implications.

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