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Examining the Association between Cannabis Use and Working Memory, Processing Speed, and Sub-Psychotic Subjective Experiences

New Zealand has among the top two highest prevalence of cannabis use in the world. Additionally, the strings of cannabis on offer in the market of New Zealand is among the most potent ones available. With these two factors at play within New Zealand society, it is important to know the effects of cannabis on mental health. Studies have suggested that regular/heavy use of cannabis can lead to psychosis, however other studies have presented findings contrary to this. Studies consistently found that individuals with psychosis performed much poorer on working memory measure via the digit-symbol subset of the WAIS. Thus this study aimed to investigate how cannabis use may relate with performance of digit-symbol performance and sub-clinical psychotic experiences. Method: A quantitative design was used to investigate relationships: between cannabis use, digit-symbol performance, and ratings of the Sub-Psychotic Subjective Experiences Scale (SPSES). Fifty one voluntary random sample participants (n=51) were included in the results of the study. 69% were aged 18-24 years, 84% of the sample population were students, and majority Europeans. Males and females were equally represented. The research sessions were conducted in an office-type laboratory environment. The first part entailed participants completing Wechsler Abbreviated Scale of Intelligence 2nd edition (WASI-II), and Wechsler Adult Intelligence Scale 3rd edition (WAIS-III) digit-symbol subtest with the researcher on a desk. Participants then moved to the computer to complete the questionnaires on background and history, cannabis use (Cannabis Use Problem Identification Test (CUPIT) and Cannabis Abuse Screening Test (CAST) questionnaires for cannabis users), and the Sub-Psychotic Subjective Experiences (SPSES) questionnaire. Results: Participants were apportioned into four cannabis use groups using self-rating measures obtained from CUPIT and CAST scores. The user groups were 1: non-users, 2: previous uses, 3: non-regular users, and 4: regular users. An overall one-way (4 cannabis use groups) MANOVA conducted on the outcome variables digit-symbol scores, and SPSES scores, with depression scores and IQ scores as covariates) revealed no significant main effects, significant interactions or any significant covariates. Subsequent Spearman’s Rank-Order coefficient, however, indicated significant correlations of cannabis use with CUPIT scores, CAST scores, and use of other recreational drugs. Pearson’s correlation coefficient was used for correlation analyses for all other ratio and interval variables. There were no significant Pearson’s correlations found. Conclusion: The study found no significant association between regular cannabis use and digit-symbol performance; nor was there a significant association between cannabis use and sub-psychotic subjective experiences ratings. Therefore, the student-majority sample did not present any significant deficits in cognitive function depending on cannabis use. Cannabis use was also not related to IQ scores or depression scores; and absence thereof.
Type of thesis
Vaka, W. (2017). Examining the Association between Cannabis Use and Working Memory, Processing Speed, and Sub-Psychotic Subjective Experiences (Thesis, Master of Social Sciences (MSocSc)). University of Waikato, Hamilton, New Zealand. Retrieved from https://hdl.handle.net/10289/11546
University of Waikato
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