Callaghan, Russell

Background/Aims. Since the early 2000s, Canada’s primary care system has undergone substantial reforms, including the incorporation of interdisciplinary teams and strategies to optimise accessibility. However, the effects of primary care accessibility and continuity of care on less-urgent emergency department (ED) use are unclear. Three studies were undertaken to investigate the effects of primary care accessibility and continuity of care factors on less-urgent ED use. Methods. Study One employed a cross-sectional analysis of responses to the Canadian Survey of Experiences with Primary Health Care to predict self-reported ED visit avoidability; Study Two employed a longitudinal time-to-event analysis of responses to Ontario’s Health Care Experience Survey linked with subsequent National Ambulatory Care Reporting System data to predict medically assessed less-urgent ED use; and Study Three employed time-series analyses of presentations to two northern British Columbia EDs following changes in walk-in clinic coverage. Results. Study One (n = 2,625) found no significant associations between self-reported ED visit avoidability and all measures of primary care accessibility and continuity of care. However, rural respondents reported greater ED visit avoidability. Conversely, Study Two (n = 34,686) found that all accessibility factors were significantly associated with medically assessed less-urgent ED use, including the presence of a regular PCP, the regular source of care, and the availability of after-hours care through the PCP. However, time with the same PCP was not associated with medically assessed less-urgent ED use. Rurality was also found to moderate the effect of after-hours care accessibility, with only rural respondents reporting a beneficial effect. Finally, Study Three found that changes in walk-in clinic coverage resulted in short-term impacts on less-urgent ED use, with a walk-in clinic closure resulting in an immediate increase in less-urgent presentations and an opening resulting in an immediate decrease. Conclusions. The findings of Studies Two and Three provide evidence that primary care accessibility factors are associated with medically assessed less-urgent ED use; however, the findings of Study One suggest that these factors do not influence self-perceived ED visit avoidability. Future studies should consider this discordance when measuring the impact of primary care accessibility on less-urgent ED use.

This thesis aimed to examine cannabis use patterns by quantity in the United States, identify key characteristics of the heaviest cannabis users, and conduct an initial assessment of whether the prevention paradox may hold for cannabis use in the United States. Using data from the National Epidemiologic Survey on Alcohol and Related Conditions – III, findings suggest that a small portion of the cannabis-using population consumes the majority of the yearly cannabis supply in the United States. Characteristics that affect the odds of being a heavy cannabis user include age, sex, personal income, education level, age of initiation, and the presence of a cannabis use or nicotine use disorder. A larger absolute number of cases experience cannabis-related harms in the low-to-moderate-using group compared to the heaviest-using group. However, a higher percentage of heavy cannabis users experience cannabis-related harms. Therefore, a dual-pronged approach of both targeted and population-based strategies may be appropriate.