The objective was to evaluate trends in marijuana exposures reported to the Colorado regional poison centre (RPC). Human exposures cases from the Colorado RPC obtained from 1 January 2000 through 31 December 2018 using generic marijuana exposure codes. There were 2221 marijuana exposures, with an increase in exposures by 11.2 cases per year (p<0.0001). Annual cases remained steady since 2014 (p=0.22), with a 19.4% increase in 2018 compared with 2017. Since 2014, the largest increase was in children age 0–8 years (p<0.0001). Edible marijuana exposures increased by 9.6 exposures per year from 2015 to 2018 (p=0.04). After observing an increase in Colorado RPC marijuana exposure cases in 2010 and 2014, annual exposures have been stable through 2017, with the first increase in legalised recreational sales era in 2018. There are specific concerns for the paediatric population and exposures involving edibles, as these cases continue to increase.
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As of May 2019, 33 states, have legalised medical marijuana, and nine states have allowed recreational marijuana.1 It is estimated in 2019, at least seven additional states are evaluating legalisation with additional discussions on federal protection.2 3 The public health implications of marijuana legalisation impacts all ages, and continued concerns exist for adverse effects from medical use and recreational overconsumption.
Colorado was one of the initial states that legalised both medical and recreational marijuana.4 Despite significant state legislative oversight, there has been an increase in local emergency department (ED) visits in all ages associated with marijuana.5–8 The Colorado regional poison centre (RPC) noted a significant increase of marijuana exposure cases after liberalisation of medical marijuana in 2010 and recreational marijuana sales in 2014.9 Since 2014, the marijuana industry has continued to grow in Colorado, increasing in sales from almost $700 million in 2014 to $1.5 billion in 2018.10 It is critical to continue close surveillance on various health impacts of marijuana legalisation. The objective of this study was to evaluate trends in Colorado RPC marijuana related exposure cases from 2000 through 2018.
Aggregate data involving closed-case, human exposures from the Colorado RPC were obtained from the National Poison Data System (NPDS) from 1 January 2000 through 31 December 2018. Information calls were excluded. Generic marijuana exposure codes (singe and poly substance) were queried from NPDS (online supplementary appendix 1). Exposures indicating synthetic marijuana analogues or pharmaceutical tetrahydrocannabinol (THC) medications (ie, Marinol, dronabinol) were excluded. Variables collected included age, gender, location of exposure, substance(s) involved (identified by generic codes), reason for exposure, type of product (online supplementary appendix 2) and symptoms. Medical outcomes, as predefined by NPDS, and symptoms reported were described for exposures to marijuana alone without other substance exposures.11 Coding for specific marijuana products began in July 2014, therefore type of product was examined from 1 January 2015 to 31 December 2018. Exposures were grouped into four age (year) categories: 0–8, 9–17, 18–24, 25 or older and unknown age. Marijuana exposures alone or with other substances were grouped into intentional and unintentional exposures.
The SAS V.9.4 statistical software package was used. Counts of reported marijuana exposures were quantified by calendar year (2000–2018) and examined over time, by age, intention, and by marijuana exposures alone or in combination with other substances. Linear regression was used to test temporal trends and a Wald χ2 was used to test year by year comparisons. Significance was determined by a p value of 0.05 or less.
From 2000 through 2018, there were 2221 total marijuana exposures reported to the Colorado RPC. Most cases were male (1210, 54.5%), with a mean age of 22.3 years (SD 16.9), and originated from the home residence (1686, 75.9%) (table 1). Overall, there was an increase in marijuana exposures by 11.2 cases per year from 2000 to 2018 (p<0.0001). Although annual exposure cases remained steady from 2014 to 2018 (p=0.22), there was a 19.4% increase in 2018 compared with 2017 (p=0.05) (figure 1). In 2018, most marijuana exposures were intentional (153, 57.5%) single-substance exposures (215, 81.1%). 2018 was the first year postlegalised recreational marijuana sales that children age 0–8 years comprised the majority of marijuana exposures (89, 33.5%), followed by adults age 25 years and older (79, 29.8%) (online supplementary appendix 3). Prior to legalised sales (2000–2013) marijuana exposures among children 0–8 increased by 1.3 exposures per year (p=0.0022). Since 2014, annual exposures increased from 45 to 89 (p<0.0001), or 10.3 exposures per year (p=0.04), the largest of any age group during legalised sales (figure 1).
From 2015 through 2018, exposures from smokeable marijuana slightly decreased from 126 to 92 (p=0.11). Edible marijuana exposures have increased from 84 (36.5%) to 111 (41.9%), or 9.6 exposures per year (p=0.04). Most products involved were from marijuana plants (393, 37.6%), but there were 253 (24.2%) exposures due to marijuana brownies, candies, or cookies, and 80 (7.6%) exposures due to a marijuana oil, concentrate, or e-cigarette. Among children age 0–8, 164 (59.6%) exposures were from edibles, increasing by 9.8 exposures per year (p=0.01).
The most common symptoms experienced by patients reporting marijuana exposures alone without other substances were other symptoms (26.7%), drowsiness/lethargy (25.3%), nausea or vomiting (23.2%) and tachycardia (13.2%). Agitation (10.0%), confusion (8.3%), dizziness/vertigo (7.5%), tremor or seizure (7.5%), hallucinations/delusions (4.3%), ataxia (4.1%), mydriasis (3.5%), headache (3.2%), dyspnoea (2.6%) and abdominal pain (2.1%) were also reported (figure 2). Other symptoms were reported but were less than 2.0% of calls with marijuana exposures alone (online supplementary appendix 4). For single substance exposures, medical outcomes included 194 (14.4%) no effects, 677 (50.4%) minor effects, 211 (15.7%) moderate effects and 15 (1.1%) major effects. There was one death reported in the cohort in an 11 months old from myocarditis, who also had postmortem blood concentrations detectable for tetrahydrocannabinol.12
After observing a significant increase in Colorado RPC marijuana exposure cases in 2010 and 2014, annual exposures have been stable through 2017, with the first increase in the postlegalised recreational sales era occurring in 2018. A significant increase in marijuana exposures in children age 0–8 years demonstrate a continued concern on the impact of legalisation on this vulnerable population. Additional concerns about edible marijuana products exist as marijuana exposures have continued to increase overall.
The overall stabilisation of Colorado RPC cases is likely multifactorial. Calls to the poison centre are self-reported and provide a public health indicator to adverse health events in the community but do not capture the full community burden. The public likely has gained more experience with marijuana products and healthcare providers are likely more knowledgeable on adverse effects, both of which may also have contributed to less RPC cases. State rules and regulations including dose limitations, child-resistant packing and educational campaigns may be making an impact on responsible and safe use.10 As more states have legalised since 2014, less marijuana tourism in Colorado could potentially have impacted annual exposure call counts.13
Despite the overall stabilisation in annual marijuana exposure counts, childhood exposures continue to increase. A regional children’s hospital in Colorado has also noted an increased in hospital visits in all ages, including adolescents.6 7 14 Accidental ingestion of edible products are of specific concern in the paediatric population, as these products are attractive and palatable. Regulations enacted in 2015 to limit THC in these products may have had an impact on hospitalisations, as there was an observed decrease in children requiring hospitalisation in 2016 and 2017.7 Recent evidence has observed safe storage of marijuana products is improving since retail legalisation.15 However, with the continued rise in exposures, it is unclear if other regulations such as child-resistant packaging, and limitations on edible product shapes and names are having an impact.
Edible products are also of concern in the adult population. Recent research demonstrated adults who had consumed edible marijuana were more likely to have acute psychiatric symptoms, intoxication and cardiovascular symptoms compared with inhaled marijuana.8 This demonstrates the need for strict regulations, public education and continued surveillance related to edible products.
There are some limitations to our study. There have been coding changes made to NPDS because of the evolving marijuana legal landscape. These changes occurred in July 2014 and again in November 2016. Though these changes improved surveillance of reported marijuana exposures, they may introduce surveillance bias and do not allow for examining trends in marijuana product type prior to 1 July 2014. RPC cases are self-reported, neither all individuals with symptoms, nor all healthcare providers managing patients with marijuana exposures call the RPC. Therefore, the number of cases reported is likely an underestimation of the number of true exposures.
As more states legalise marijuana, it is critical that state public health agencies continue to survey the health impact on all populations. In Colorado, overall annual exposure cases to RPC appear to have stabilised, but childhood exposures and adverse effects related to edible marijuana products have increased. Poison centre data remains an important tool for public health by serving as a barometer for what is happening in the community. Continued research on physical and mental health impact, along with the effect (1) on regulatory interventions are necessary to limit these public health consequences after marijuana legalisation.
What is already known on this subject
The Colorado regional poison centre noted a significant increase of marijuana exposure cases after liberalisation of medical marijuana in 2010 and recreational marijuana sales in 2014.
What this study adds
After annual exposures stabilised between 2014 through 2017, an increase in the postlegalised recreational sales era occurred in 2018.
A significant increase in marijuana exposures in children age 0–8 years demonstrate a continued concern on the impact of legalisation on this vulnerable population.
Additional concerns about edible marijuana products exist as marijuana exposures have continued to increase overall.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests DSW receives royalties from UpToDate for authorship contributions to related topics. The remaining authors have no COI.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
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