The impact of recreational cannabis legalization on cannabis-related acute care events among adults with schizophrenia

doi:10.21203/rs.3.rs-4720313/v1

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Research Article

The impact of recreational cannabis legalization on cannabis-related acute care events among adults with schizophrenia

https://doi.org/10.21203/rs.3.rs-4720313/v1

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Purpose

Patients with schizophrenia have a higher risk of cannabis use disorder and may be uniquely affected by the legalization of recreational cannabis. This study examined whether cannabis legalization led to changes in acute care utilization among patients with schizophrenia.

Method

Using linked health administrative data, we included adult patients with schizophrenia in Ontario from October 2015 to May 2021 (n = 121,061). We examined the differences in cannabis, psychosis, and mental health-related emergency department (ED) visits over three periods: pre-legalization, legalization of flowers and herbs (phase 1), and legalization of edibles, extracts, and topicals (phase 2) using interrupted time-series methods.

Results

Our study found that phase 1 was associated with decreases in cannabis-related, mental health-related, and cannabis + psychosis-related ED visits among the patients with schizophrenia. Notably, an immediate 25.8% (95% CI 13.8–37.6%) decrease in cannabis-related ED visits was observed in men, and an immediate 18.5% decrease in mental health-related ED visits (95% CI 6.0–31.2%) in women. These decreases were also shown in the comparative ITS models, demonstrating that the changes observed were distinct from trends in the general population. However, phase 2 was not associated with any significant changes.

Conclusions

Despite higher baseline rates of acute care utilization among patients with schizophrenia, cannabis legalization was associated with significant reductions, particularly during phase 1. Our findings suggest that regulatory measures accompanying legalization could enhance the quality and safety of cannabis products, potentially leading to fewer adverse health outcomes in vulnerable patient populations. Further research is needed to optimize healthcare responses for this vulnerable population.

schizophrenia

legalization

cannabis

acute care

emergency department

Canada

Since the legalization of recreational cannabis in Canada on October 17, 2018, there have been a number of studies to investigate the impact of cannabis legalization on cannabis-related hospitalizations and emergency department (ED) visits in the general population^1–3; however, the effects of legalization on patients with schizophrenia remains unknown. There are a number of reasons why we should investigate the impact of legalization on this clinical population.

First, in a meta-analysis on cannabis-use disorder among patients diagnosed with schizophrenia, approximately 16% had a concurrent cannabis-use disorder, while 25% had a cannabis-use disorder in their lifetime⁴ - compared to 7.2% with cannabis-use disorder (lifetime) in the general population⁵. The high prevalence of cannabis-use disorder in this clinical population may mean that the impact of increasing accessibility of cannabis products can lead to more adverse events among this patient group, and in turn leading to higher cannabis-related ambulatory care and hospitalizations. Second, based on the National Cannabis Survey of the general adult population conducted by Statistics Canada, between Q1 2018 and Q4 of 2020, there was a 46.3% increase in the number of participants reporting near daily cannabis use⁶. Legalization may also have led to an increase of frequent/near daily use among patients with schizophrenia. In prior studies, frequent or near daily use of cannabis has been shown to exacerbate symptom severity and increase rates of hospitalization in patients previously diagnosed with schizophrenia even among stable patients treated with antipsychotics⁷. One potential explanation is that the psychoactive component in cannabis, tetrahydrocannabinol (THC), reverses the neurobehavioral effects of certain antipsychotic drugs such as risperidone, which has been demonstrated in a mouse model study⁸. In the clinical setting, people with a diagnosis of schizophrenia who used cannabis were prescribed more unique antipsychotics on average than those who were not using cannabis. Thus, cannabis use may contribute to decreased effectiveness of antipsychotics treatments⁹. Finally, in a meta-analysis on cannabis use and adherence to antipsychotic medications, cannabis users had 5.8 times higher odds of antipsychotic non-adherence than non-users, suggesting that cannabis use may lead to treatment non-compliance via lowered inhibition and reduced judgment¹⁰

Based on these factors, we investigated whether cannabis legalization may lead to changes in cannabis-related ED utilization among patients diagnosed with schizophrenia in Ontario. In addition, we further investigated whether cannabis legalization was followed by an increase in psychosis-related ED visits¹¹, given that cannabis-related psychosis may be difficult to differentiate from non-cannabis-related psychosis in the ED setting. Finally, we investigated whether cannabis legalization had a generalized effect on mental health for individuals with schizophrenia, which helps to identify possible patterns even in the face of misclassifications in the ED. Since Ontario’s cannabis legalization underwent a multi-phased approach, we tested the association between cannabis-related acute care and each of the two phases of legalization. The initial phase, Phase 1 (October 2018-March 2020), saw the introduction of provincial government-operated online flower and herb sales alongside limited private retail storefronts. Phase 2 (March 2020-May 2021) involved the expansion of storefronts and increased availability of cannabis edibles.

Data source and study population

The study cohort includes all adult patients eligible for provincial universal healthcare (OHIP) diagnosed with schizophrenia (ICD-8 code: 295) up to 5 years before legalization. Patients who were 18 and over at the time of legalization, with continuous OHIP coverage and residency in Ontario for the entire study period (October 2015 and May 2021) were included in the study (n = 12,079,699). Health administrative data was accessed through ICES (formerly the Institute for Clinical Evaluative Sciences). The eligible patients were followed between October 2015 and May 2021 using the National Ambulatory Care Reporting System (NACRS). Our study followed Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guidelines. Ethics approval for this study was obtained through York University (REB#-2022-254).

Population at risk

We identified individuals diagnosed with schizophrenia using a previously validated algorithm^12,13. The algorithm combines physician service claims with hospitalization data using the following codes: ICD-10 F20 and F25; DSM-IV 295.70 and 295.70; and OHIP diagnostic code 295. The sensitivity of capturing the cases using physician service claims in addition to hospitalization data ranges from 90.1–98.8%, with a positive predictive value of up to 71.1%.

Exposure: cannabis-related policy in Ontario

To examine the impact of recreational cannabis policy on cannabis-related ED visits among individuals diagnosed with schizophrenia, we used three distinct time periods related to the Ontario legal cannabis availability: 1) the pre-legalization period (October 2015-October 2018), 2) Phase 1 of legalization (October 2018-February 2020), when flower and herb were available online and at limited physical retail locations, and 3) Phase 2 (March 2020-May 2021), which marked the rapid retail expansion (removal of provincial retailer cap) alongside increased edible cannabis availability. These time periods have been used in prior studies on cannabis-related ED visits following cannabis legalization and commercialization in the Ontario population ¹⁴. Cannabis-related ED visits between March and April 2020 were censored to account for significant decreases in healthcare utilisation at the onset of the COVID-19 pandemic, as suggested by prior literature¹⁵.

Outcomes

The outcome of the study was monthly ED visits (log-transformed) from October 2015 to May 2021 in Ontario (the count of the event by gender for each month within the study period). We used 3 outcomes in our study, including 1) cannabis-related ED visits, 2) cannabis-related ED visits combined with psychosis-related ED visits, and 3) all mental health ED visits. All outcomes were collected from the National Ambulatory Care Reporting System (NACRS). Outcome #1 focused on cannabis-related visits which include F12 (mental and behavioural disorders related to cannabis) and T40.7 (cannabis poisoning), which were commonly used in prior studies^16,17. Outcome #2 adds in all psychosis-related ED visits¹¹ (see codes and details in Table S1), since cannabis-related psychosis (included in outcome #1) may be difficult to differentiate from non-cannabis-related psychosis in the ED setting. Outcome #3 includes all mental health ED visits (F00-F99)¹⁸, since we wanted to check whether cannabis legalization had a generalized effect on mental health for individuals with schizophrenia, and serves as a robustness check on the first 2 outcomes. For each outcome variable, we aggregated the acute care record data into monthly data.

Statistical analysis

To examine the immediate and month-to-month changes related to cannabis-related policies on cannabis-related healthcare utilization among patients diagnosed with schizophrenia by gender. We first used single interrupted time series analysis in individuals with schizophrenia based on the monthly incidence rate. These analyses were performed separately for men and women to investigate the immediate (level) changes and trend (month-to-month) changes across the key time periods (i.e. pre-legalization, phase 1, and phase 2) for all 3 outcomes. The model is specified as follows:

$$\:{Y}_{t}\:=\:{\beta\:}_{0}+{\beta\:}_{1}{T}_{t}+{\beta\:}_{2}{X}_{1t}+{\beta\:}_{3}{X}_{1t}{T}_{1t}+{\beta\:}_{4}{X}_{2t}+{\beta\:}_{5}\:{X}_{2t}{T}_{2t}+{\epsilon\:}_{t}\:$$

where Y_t is the Log transformed monthly ED visits at time-point t respectively. T_t is the time since the start of the study at time point t and X_tT_t is an interaction term. 𝛽2 represents the change in the level of the outcome immediately following the cannabis legalization (Phase 1). 𝛽4 represents the change in the level of the outcome immediately following Phase 2. Change in slope in the pre-legalization period is represented by 𝛽0, while 𝛽1 and 𝛽3 are summed to represent slope in phase 1, and 𝛽1, 𝛽3 and 𝛽5 are summed to represent slope in phase 2. See details in the supplementary table 1 for the full explanations for every parameter that are used in our analyses.

Second, we conducted a comparative interrupted time series model to compare changes in individuals with schizophrenia vs. the general population. This comparison offers insights into whether the changes observed in the schizophrenia group are unique to this group or if similar changes are seen in the general population. By distinguishing these differences, we aim to establish whether cannabis legalization uniquely impacted schizophrenia patients in Ontario. We used a user-written package for ITSA¹⁹ to compare trends and characteristics of ED visits over three periods: pre-legalization, Phase 1, and Phase 2:

$$\:{Y}_{t}\:=\:{\beta\:}_{0}+{\beta\:}_{1}{T}_{t}+{\beta\:}_{2}{X}_{1t}+{\beta\:}_{3}{X}_{1t}{T}_{1t}+{\beta\:}_{4}{Z}_{}+{\beta\:}_{5}Z\:{T}_{t}+{\beta\:}_{6}Z\:{X}_{1t}+{\beta\:}_{7}Z\:{X}_{1t}{T}_{1t}+{\beta\:}_{8}{X}_{2t}\:$$

$$\:+{\beta\:}_{9}{X}_{2t}{T}_{2t}+{\beta\:}_{10}Z\:{X}_{2t}+{\beta\:}_{11}Z\:{X}_{2t}{T}_{2t}+{\epsilon\:}_{t}$$

where Y_t is the Log transformed monthly ED events at time-point t. Z is the dummy variable denoting cohort assignment status (schizophrenia (= 1) vs. general population (= 0)), while X is the dummy variable denoting cannabis legalization phases, with X_1t for phase 1 of legalization and X_2t for phase 2. T_t is the time since the start of the study at time point t and X_tT_t is an interaction term. Detailed descriptions of the dummy variables X_1t and X_2t, and continuous variables T_t, T_1t, and T_2t are presented in supplementary tables 3 and table 4. $\:{\beta\:}_{1}$, $\:{\beta\:}_{2}$, $\:{\beta\:}_{3}$, $\:{\beta\:}_{8}$, and $\:{\beta\:}_{9}$ refer to parameters for the control group (i.e. general populations), and$\:{\:\beta\:}_{5}$, $\:{\beta\:}_{6}$, $\:{\beta\:}_{7}$, $\:{\beta\:}_{10}$, and $\:{\beta\:}_{11}$ are used to modify the former coefficients to estimate the parameters of interest for the schizophrenia group. For example, the change in slope in the pre-legalization period for the general population is represented by $\:{\beta\:}_{1}$, while $\:{\beta\:}_{1}$ and $\:{\beta\:}_{5}$ are summed to represent the pre-legalization slope for the schizophrenia group. $\:{\beta\:}_{4}$ represents the difference in the level (intercept) of the outcome variable between the target and comparison groups prior to the intervention; however, it is not used in the parameter estimation because it is not of interest in our study. See supplementary table 2 for the detailed explanations of every parameter used in our analyses. Two gender-stratified models were specified. We conducted additional analyses to check the robustness of our findings. We rerun both the single ITS model in individuals with schizophrenia and the comparative ITS model between individuals with schizophrenia and the general population using cannabis-related ED visits + psychosis-related + schizophrenia-related ED visits as an additional outcome. STATA v17 was used for our data analysis. Each test (post-estimation analysis) was two-tailed with 5% as alpha to test statistical significance.

[Table 1]

Table 1

**Rates of cannabis-related ED visits per 100,000 individuals over the study periods among individuals diagnosed with schizophrenia**
	Men			Women
	Pre-legalization	Phase 1	Phase 2	Pre-legalization	Phase 1	Phase 2
Cannabis	172.47 (29.20)	155.15 (15.99)	166.32 (26.92)	64.75 (15.33)	61.40 (9.99)	63.29 (14.00)
cannabis + psychosis	90.54 (17.22)	76.42 (11.13)	85.47 (17.11)	21.67 (6.51)	17.26 (4.99)	20.26 (6.30)
All mental health	46.32 (9.91)	43.84 (7.78)	45.30 (9.34)	9.44 (4.15)	7.10 (3.61)	8.67 (4.07)

Rates of Cannabis-related, cannabis-related ED visits + psychosis-related ED visits, and all mental health ED visits by gender in each phase of cannabis-related policy are presented in Table 1. A consistent pattern shows reductions in the rates of all outcomes during phase 1 compared to the pre-legalization period, where the rates of cannabis-related ED visits were 172.47 for men and 64.75 for women. Slight increases were observed during phase 2, with the rates of cannabis-related ED visits rising to 166.32 for men and 63.29 for women.

[Figure 1]

Figure 1 and Table S2 show the single ITS model stratified by gender in schizophrenia patients for our three main outcomes. In the pre-legalization period, there were small month-to-month increases in the number of cannabis-, mental health-, and cannabis + psychosis-related ED visits in both males and females (each around an increase of 0.01 events per 100,000 population per month). Phase 1 was associated with the following immediate decreases for men with schizophrenia: a 25.8% decrease in cannabis-related ED visits (95% CI 13.8–37.6%), an 11.6% decrease (95% CI 4.4–18.7%) in mental health-related ED visits, and a 38.4% decrease in cannabis + psychosis-related ED visits (95% CI 21.9–55.0%). Additionally, there was a 1% decrease per month (95% CI 1.4–0.5%) in mental health-related ED visits. For women with schizophrenia, there was an immediate 18.5% decrease in mental health-related ED visits (95% CI 6.0–31.2%), but no immediate change was observed in cannabis-related ED visits and cannabis + psychosis-related ED visits. Furthermore, the Phase 1 period was associated with a 1.3% decrease per month (95% CI 0.1–2.5%) in cannabis-related ED visits in this group. Phase 2 was not significantly associated with any immediate or trend changes across our three outcomes in men with schizophrenia. However, Phase 2 was associated with an immediate 7.2% decrease in mental health-related ED visits (95% CI 5.9–20.4%) for women with schizophrenia.

[Table 2]

Table 2

Comparative interrupted time-series analyses: comparison of trends between schizophrenia patients and general population stratified by sex
	schizophrenia (A)	General population (B)	Difference test (A)-(B)
Outcome #1: Cannabis-related ED visits
Male
Pre-legalization trend	0.013*** (0.009 to 0.017)	0.016*** (0.014 to 0.018)	-0.003 (-0.007 to 0.002)
Phase 1 intercept change	-0.256*** (-0.377 to -0.135)	0.152*** (0.063 to 0.240)	-0.408*** (-0.558 to -0.258)
Phase 1 slope change	-0.010 (-0.022 to 0.003)	-0.005 (-0.013 to 0.002)	-0.005 (-0.019 to 0.010)
Phase 2 intercept change	0.084 (-0.111 to 0.281)	0.074 (-0.171 to 0.320)	0.010 (-0.304 to 0.325)
Phase 2 slope change	0.003 (-0.012 to 0.019)	0.010 (-0.015 to 0.033)	-0.006 (-0.034 to 0.023)
Female
Pre-legalization trend	0.010*** (0.004 to 0.017)	0.016*** (0.014 to 0.018)	-0.006 (-0.013 to 0.001)
Phase 1 intercept change	-0.127 (-0.317 to 0.063)	0.146*** (0.072 to 0.220)	-0.273*** (-0.477 to -0.070)
Phase 1 slope change	-0.013* (-0.025 to -0.001)	-0.005 (-0.011 to 0.001)	-0.008 (-0.021 to 0.006)
Phase 2 intercept change	-0.083 (-0.101 to 0.291)	0.095 (-0.101 to 0.291)	-0.178 (-0.484 to 0.127)
Phase 2 slope change	0.018 (-0.005 to 0.041)	0.007 (-0.005 to 0.041)	0.011 (-0.020 to 0.041)
Outcome #2: Mental health-related ED visits
Male
Pre-legalization trend	0.009*** (0.006 to 0.012)	0.008*** (0.005 to 0.012)	0.000 (-0.004 to 0.005)
Phase 1 intercept change	-0.100* (-0.179 to -0.038)	0.135*** (-0.082 to -0.020)	-0.130* (-0.241 to -0.019)
Phase 1 slope change	0.010*** (-0.015 to -0.005)	0.002 (-0.004 to 0.008)	-0.012** (-0.020 to -0.004)
Phase 2 intercept change	0.012 (-0.114 to 0.138)	-0.185 (-0.378 to 0.007)	0.197 (-0.032 to 0.427)
Phase 2 slope change	-0.005 (-0.020 to 0.011)	0.012 (-0.005 to 0.029)	-0.017 (-0.041 to 0.007)
Female
Pre-legalization trend	0.009*** (-0.004 0.013)	0.009*** (0.006 to 0.012)	0.000 (-0.006 to 0.005)
Phase 1 intercept change	-0.164* (-0.304 to -0.024)	0.026 (-0.051 to 0.104)	-0.191* (-0.351 to -0.031)
Phase 1 slope change	-0.001 (-0.054 to 0.052)	0.000 (-0.005 to 0.004 )	-0.001 (-0.054 to 0.052)
Phase 2 intercept change	-0.068 (-0.209 to 0.071)	-0.174 (-0.360 to 0.012)	0.105 (-0.127 to 0.338)
Phase 2 slope change	0.000 (-0.011 to 0.012)	0.011 (-0.006 to 0.028)	-0.011 (-0.032 to 0.009)
Outcome 3#: Cannabis- and psychosis-related ED visits
Male
Pre-legalization trend	0.012*** (0.007 to 0.016)	0.006*** (0.005 to 0.008)	0.006* (0.001 to 0.010)
Phase 1 intercept change	-0.381*** (-0.550 to -0.212)	0.251*** (0.174 to 0.328)	-0.632*** (-0.818 to -0.446)
Phase 1 slope change	0.000 (-0.014 to 0.014)	-0.003 (-0.010 to 0.004)	0.003 (-0.013 to 0.019)
Phase 2 intercept change	0.007 (-0.230 to 0.244)	0.194** (0.056 to 0.332)	-0.187 (-0.462 to 0,087)
Phase 2 slope change	0.009 (-0.011 to 0.028)	0.000 (-0.012 tp 0,013)	0.008 (-0.015 to 0.032)
Female
Pre-legalization trend	0.013*** (0.007 to 0.019)	0.006*** (0.005 to 0.007)	0.007* (0.000 to 0.013)
Phase 1 intercept change	-0.245 (-0.529 to 0.039)	0.258*** (0.193 to 0.323)	-0.503 ** (-0.794 to -0.212)
Phase 1 slope change	-0.025 (-0.052 to 0.001)	-0.004 (-0.009 to 0.002)	-0.022 (-0.049 to 0.005)
Phase 2 intercept change	0.300 (-0.037 to 0,636)	0.207*** (0.098 to 0.317)	0.092 (-0.262 to 0.446)
Phase 2 slope change	-0.004 (-0.035 to 0.027)	-0.001 (-0.011 to 0.010)	-0.003 (-0.035 to 0.029)

Table 2 presents the comparative ITS model with gender-disaggregated results, which contextualizes the changes among patients with schizophrenia in relation to the general population. With regards to the pre-legalization period, while positive trends were shown under single ITS in each outcome for both men and women, results from comparative ITS models show that these increases are similar to those seen in the general population. With regards to Phase 1, the immediate decreases in many ED-visit outcomes among schizophrenia patients stood in contrast to immediate increases in ED-visits among the general population. Difference tests showed the relative change in rates were significant in the following ways: 1) among men, the immediate change in cannabis-related ED visits (-0.408, 95% CI -0.558 to -0.258), mental health-related ED visits (-0.130 95% CI -0.241 to -0.019) and cannabis + psychosis-related ED visits (-0.632, 95%CI -0.818 to -0.446) were lower among men with schizophrenia than men in the general population; 2) among women, the immediate change in cannabis-related ED visits (-0.273 95%CI -0.477 to -0.070), mental health related-ED visits (-0.191 95%CI -0.351 to -0.031) and cannabis + psychosis-related ED visits (-0.503 95%CI -0.794 to -0.212) were lower in those with schizophrenia compared to women in the general population. With regard to phase 2, there was no evidence that changes in the schizophrenia groups were significantly different than the general population.

Additional analyses (in Table S3 and S4) using a broader definition of ED visits (i.e. combining cannabis-related ED visits, psychosis-related ED visits, with schizophrenia-related ED visits) as an additional outcome reported similar results (i.e. immediate relative reductions in the schizophrenia groups in phase 1, no relative differences in phase 2).

Our study on Ontario’s population of patients diagnosed with schizophrenia found that recreational cannabis legalization (phase 1) was associated with decreases in cannabis-related ED visits (in men and women), mental health-related ED visits (in men and women), and cannabis + psychosis-related ED visits among the schizophrenia patients (in men only). These decreases were shown in both the single interrupted time series models and the comparative ITS models, demonstrating that the changes observed were distinct from trends in the general population. However, phase 2 was not associated with any significant changes.

One possible explanation for this observed decrease in ED visits among individuals with schizophrenia following cannabis legalization is that before legalization, cannabis consumers had to obtain products from the illicit market, where the tetrahydrocannabinol (THC) content levels of illegal cannabis can vary widely ranging from 5–90%^20,21. This variation can lead to unpredictable effects and higher risks of adverse reactions, including exacerbation of psychosis symptoms, which could result in more ED visits. Legalization brought about regulation and standardization of THC levels in cannabis products, providing more consistent and safer options for consumers. This reduction in THC variability might have contributed to the decrease in adverse reactions and consequently fewer ED visits. Furthermore, legal cannabis products are required to provide accurate labelling of their THC content, offering customers detailed labelling information, and reducing the likelihood of overconsumption and severe psychiatric reactions. Given the availability of regulated markets, another explanation for the reduction in ED visits could be attributable to the decrease in the risk of consuming laced cannabis. Cannabis from the illicit market was more likely to contain dangerous substances (e.g, synthetic cannabinoids, cocaine, and LSD)^22–24, leading to severe health risks²⁵. Regulation accompanied by legalization includes testing for contaminants and discourages the practice, ensuring safer products.

This suggests that increased accessibility following legalization does not necessarily translate to heightened acute-care utilization for patients with schizophrenia. In a study based in one of three psychiatric ED visits in Quebec City, the researchers found no increase in the incidence of cannabis-related psychotic episodes after legalization²⁶. However, since the proportion of individuals with schizophrenia is small (1% or under)²⁷, unless a study identifies a schizophrenia patient cohort and follows them over time, we still cannot understand the impact of legalization on this patient group. Moreover, since the sample is based on a single clinical setting, it is unlikely to be generalizable to schizophrenia patients. Similarly, a prior study using interrupted time-series models has found that cannabis legalization was not associated with significant changes in cannabis-induced psychosis or schizophrenia ED presentations during the 14.5-month post-legalization period in Ontario and Alberta, Canada; and similarly, they reported no evidence that the legalization led to increases in alcohol-induced psychosis and amphetamine-induced psychosis²⁸. While these findings are consistent with our results, they also did not examine a schizophrenia patient group over time, which may be differentially affected by cannabis legalization.

There are some limitations to our study. First, individuals with schizophrenia who have not yet been diagnosed are excluded from our study, which introduces a potential selection bias - by including only those who are actively engaged with the healthcare system. Consequently, our sample may consist of schizophrenia patients who are in comparatively better health. Second, our study is based on a single setting in Ontario, which may limit the generalizability of the results to other regions or countries with different healthcare systems, cannabis policies or population characteristics. Third, the COVID-19 pandemic might have an impact on both cannabis consumption and acute care utilization in phase 2. However, our comparative interrupted time-series models report similar findings, which suggest that the impact of the pandemic did not significantly have differential impacts on the patients with schizophrenia and the general population.

Our study uniquely contributes to understanding how cannabis policies can influence healthcare utilization among a vulnerable clinical population. Our findings suggest that regulatory measures accompanying legalization could enhance the quality and safety of cannabis products, potentially leading to fewer adverse health outcomes in vulnerable patient populations. Furthermore, our study indicates that legalization and cannabis regulation, in certain contexts, may help reduce acute care utilization in vulnerable patient groups. The potential benefits of legalization are more likely to occur by adopting harm-reduction strategies in cannabis regulation. Policymakers should focus on reducing the risks associated with cannabis use, such as contamination and overconsumption, to potentially reduce adverse health outcomes. This includes implementing stringent quality control standards, ensuring accurate labelling of THC content, and providing public health education on safe cannabis use. By prioritizing these harm-reduction strategies, policymakers can create a safer environment for cannabis consumers, particularly those with schizophrenia, and potentially improve public health outcomes.

Data availability statement

The dataset from this study is held securely in coded form at the Institute for Clinical Evaluative Sciences (ICES). While data sharing agreements prohibit ICES from making the dataset publicly available, access may be granted to those who meet pre-specified criteria for confidential access, available at www.ices.on.ca/DAS. The full dataset creation plan and underlying analytics code are available from the authors upon request, understanding that the computer programs may rely upon coding templates or macros that are unique to ICES and are therefore either inaccessible or may require modification.

Acknowledgements
This study contracted ICES Data & Analytic Services (DAS) and used de-identified data from the ICES Data Repository, which is managed by ICES with support from its funders and partners: Canada’s Strategy for Patient-Oriented Research (SPOR), the Ontario SPOR Support Unit, the Canadian Institutes of Health Research and the Government of Ontario. The opinions, results and conclusions reported are those of the authors. No endorsement by ICES or any of its funders or partners is intended or should be inferred. Parts of this material are based on data and information compiled and provided by CIHI. However, the analyses, conclusions, opinions, and statements expressed herein are those of the author, and not necessarily those of CIHI.

Declaration of Conflicting Interests

None.

Funding

Funding for the study was provided by the Canadian Institutes of Health Research (Project Grant FRN# 173447, NPI: Antony Chum). The funding agencies had no role in the design and conduct of the study; the collection, management, analysis or interpretation of the data; the preparation, review or approval of the manuscript; or the decision to submit the manuscript for publication. The principal investigator (Antony Chum) is funded by the Canada Research Chair program (CRC-2021-00269).

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The impact of recreational cannabis legalization on cannabis-related acute care events among adults with schizophrenia

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Abstract

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INTRODUCTION

METHODS

Data source and study population

Population at risk

Exposure: cannabis-related policy in Ontario

Outcomes

Statistical analysis

RESULTS

DISCUSSION

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Supplementary Files

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