Does cannabis legalisation change healthcare utilisation? A population-based study using the healthcare cost and utilisation project in Colorado, USA

Francesca N Delling, Eric Vittinghoff, Thomas A Dewland, Mark J Pletcher, Jeffrey E Olgin, Gregory Nah, Kirstin Aschbacher, Christina D Fang, Emily S Lee, Shannon M Fan, Dhruv S Kazi, Gregory M Marcus

BMJ Open, 2019, 9:e027432

http:// dx.doi. org/ 10. 1136/ bmjopen- 2018-027432).

Abstract

Objective : To assess the effect of cannabis legalisation on health effects and healthcare utilisation in Colorado (CO), the first state to legalise recreational cannabis, when compared with two control states, New York (NY) and Oklahoma (OK).
Design : We used the 2010 to 2014 Healthcare Cost and Utilisation Project (HCUP) inpatient databases to compare changes in rates of healthcare utilisation and diagnoses in CO versus NY and OK.
Setting : Population-based, inpatient.
Participants : HCUP state-wide data comprising over 28 million individuals and over 16 million hospitalisations across three states.
Main outcome measures : We used International Classification of Diseases-Ninth Edition codes to assess changes in healthcare utilisation specific to various medical diagnoses potentially treated by or exacerbated by cannabis. Diagnoses were classified based on weight of evidence from the National Academy of Science (NAS). Negative binomial models were used to compare rates of admissions between states.
Results : In CO compared with NY and OK, respectively, cannabis abuse hospitalisations increased (risk ratio (RR) 1.27, 95% CI 1.26 to 1.28 and RR 1.16, 95% CI 1.15 to 1.17; both p<0.0005) post-legalisation. In CO, there was a reduction in total admissions but only when compared with OK (RR 0.97, 95% CI 0.96 to 0.98, p<0.0005). Length of stay and costs did not change significantly in CO compared with NY or OK. Post-legalisation changes most consistent with NAS included an increase in motor vehicle accidents, alcohol abuse, overdose injury and a reduction in chronic pain admissions (all p<0.05 compared with each control state).
Conclusions : Recreational cannabis legalisation is associated with neutral effects on healthcare utilisation. In line with previous evidence, cannabis liberalisation is linked to an increase in motor vehicle accidents, alcohol abuse, overdose injuries and a decrease in chronic pain admissions. Such population-level effects may help guide future decisions regarding cannabis use, prescription and policy.

Introduction

Over 147 million people, or 2.5 per cent of the world’s population, use cannabis (marijuana),1 and more than 20 million Americans have reported the use of cannabis in the past 30 days.1 Because cannabis use is a federal crime, clinical studies have been challenging to pursue resulting in substantial knowledge gaps regarding actual health consequences. Thirty-three states and the District of Columbia now allow cannabis for the treatment of medical conditions.2 Of these, nine have recently legalised cannabis for recreational use. Given such pervasive policy changes, understanding potential shifts in healthcare utilisation is vital.

Recently, an extensive and rigorous summary of the current evidence on health effects of cannabis was developed by a committee of experts appointed by the US National Academy of Science (NAS) focusing on systematic reviews and high-quality primary research.3 The health endpoints assessed in the NAS summary included oncological, cardiometabolical, respiratory immunological and psychiatric disorders as well as outcomes related to injury and death (ie, motor vehicle accidents). While the NAS summary represents a valuable starting place that makes use of the available data, we do not yet know whether that evidence, based largely on small studies, will translate into real-world ramifications after legalisation of recreational cannabis.

On 10 December, 2012, Colorado enacted Colorado Amendment 64, legalising recreational cannabis. Following this date, adults aged 21 or older could grow cannabis plants privately, legally possess all cannabis from these plants and give cannabis as a gift to other adults aged 21 or older.4 After 1 January, 2014, recreational cannabis could be legally purchased in retail stores.5 We hypothesised that changes in healthcare utilisation and diagnoses most consistent with NAS-based evidence occur when access to recreational cannabis becomes liberalised.

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