Tags:  Cannabis; cohort studies; epidemiology; health services; public health

 

Thumbnail:  Patients are more likely to see a doctor in the month after they begin using medical cannabis.

 

The problem: Although medical cannabis use is common, we don’t know what effect it has on the use of medical services. It’s possible that medical cannabis could reduce physician and hospital visits by relieving symptoms and improving health, but we don’t know whether that’s true. Past studies have shown no effect of medical cannabis usage on hospitalizations and emergency room visits, but these conclusions are limited by inconsistent findings and small sample sizes.

 

The study: The study included 9,925 adults who were authorized to use medical cannabis at specialized clinics in Ontario, Canada. The study also included 17,732 control patients, who lacked medical authorizations. All participants were assessed over a six-month period between 2014 and 2017. Their healthcare utilization after beginning cannabis use was measured in terms of physician visits, hospitalizations, and emergency room visits. The study controlled for factors such as age, sex, income, and health history.

 

Main results:

• In the first month, there was an initial increase in physician visits of 4,330 per 10,000 patients among authorized medical cannabis patients as compared to nonauthorized patients

• Across the total 6-month time period, there was a net decrease of 1,354 visits per 10,000 patients

• Overall, there was no statistical difference in healthcare utilization observed between authorized and unauthorized users

• A similar trend was observed for hospitalizations

• The only exception among healthcare outcomes was observed for emergency room visits. After no initial change in emergency room visits, there was a total of ~20 less visits per 10,000 across the 6-month period

 

Conclusions:  Medical cannabis use seems to be associated with an increase in utilization for the first month. 

 

Why this is a good study:

• This study has a large sample size of almost 10,000 authorized medical cannabis users as well as over 17,000 control patients

• Every patient who received medical cannabis was matched with up to three controls based on age, sex, Local Health Integration Network location, income, and history of other medical conditions

• To measure downstream healthcare utilization, the study also was limited to patients who were registered as eligible for Ontario Health Care Insurance Plan

 

Why this isn’t a perfect study:

• It is unclear what caused the initial spike and subsequent decline in healthcare utilization

  • It is possible that hospitalizations increased in the first month because authorized patients were interacting with physicians more frequently, giving physicians more opportunities to observe and identify conditions that require hospitalization

  • It is also possible that whatever health issue led to the medical cannabis authorization was also causing the increased healthcare utilization (e.g. a new diagnosis)

• The drug usage habits of unauthorized control patients are also unclear

 

What this study adds:

• Within the first month, there was an increase in healthcare utilization among medical cannabis users, but that increase diminishes over time.

 

What it doesn’t:

• It does not explain why authorized users had a one-month spike in healthcare utilization. That spike may be due to risk associated with authorized medical cannabis use, or it may just be due to increased interactions with physicians who refer patients for medical care for reasons having nothing to do with cannabis.

 

Funder:  This study received funding from a Canadian Institutes of health research Project grant.

 

Author conflicts:  Jason Dyck (JD) is on the board of directors of Aurora Cannabis, a for-profit company licensed for the cultivation and sale of medical cannabis. John G Halon (JGH) has worked as a paid advisor and speaker for Canadian Cannabis Clinics. Both authors have a financial interest in Aurora Cannabis. Dean Eurich (DE) holds a Mitacs Grant with Aurora as a partner. The ICES Data Repository, managed by the Institute of Clinical Evaluative Sciences with support from its funders and partners, is used as a source of data. 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.