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Thinking matters: The profile of executive functioning associated with cannabis use in schizophrenia and its functional outcome correlates

Highet, Khristin (2015) Thinking matters: The profile of executive functioning associated with cannabis use in schizophrenia and its functional outcome correlates. Professional Doctorate thesis, Murdoch University.

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Abstract

Not only is there a high prevalence of cannabis use in schizophrenia, but long-term or heavy cannabis users are also considered to demonstrate deficits similar to the cognitive endophenotypes of the illness itself. The specific neurocognitive domain of executive function has particular clinical relevance as executive dysfunction has been found to be significantly associated with the functional outcomes of schizophrenia patients. The current study sought to examine the pattern of executive functioning in schizophrenia patients with cannabis use and its functional outcome correlates. Eleven measures guided by a hierarchical model of executive function were administered to 28 schizophrenic outpatients with cannabis use and 28 matched-controls with a similar cannabis use history. Premorbid IQ and ‘real-world’ functional outcome were also assessed. A series of ANCOVA’s revealed that patients with cannabis use demonstrated poorer performances on a number of executive function measures relative to controls. However, further analysis indicated that a significantly larger proportion of this sample showed performances that did not fall in the range of clinical impairment. Using multiple regression analyses, a retrospective memory and an interference control task were found to significantly contribute to ‘real-world’ functional outcome. A lack of clinical impairment in the executive functioning of a representative sample of schizophrenia patients with cannabis use may be suggestive of differential and subtle deficits in this subgroup. Retrospective memory and interference control abilities may also present as potential targets helping to better inform rehabilitation planning efforts for such patients. Evaluating different subgroups of schizophrenia from a neurocognitive viewpoint should be an important consideration for treating clinicians particularly when attempting to achieve more successful functional outcomes.

Publication Type: Thesis (Professional Doctorate)
Murdoch Affiliation: School of Psychology and Exercise Science
Supervisor: Gouldthorp, Bethanie, Harbaugh, Allen Gregg and Reid, Corinne
URI: http://researchrepository.murdoch.edu.au/id/eprint/28738
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