Adverse Health Effects of Marijuana Legalization
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BACKGROUND: Washington State has been at the forefront of modern-day marijuana legislation for over two decades. In November 1998, Washington State became one of the first states to legalize medical marijuana and, nearly 15 years later, Washington State became one of two states to legalize marijuana for recreational purposes. Such legislation was unprecedented not only in the United States but also internationally. There is much interest in the potential health impacts of such unique legislation and, to date, few studies have evaluated the health effects of both medical and recreational marijuana legalization in Washington State. OBJECTIVES: The specific aims of this study were to: 1) evaluate the ability of International Classification of Diseases, Clinical Modification (ICD-CM) codes available in an administrative hospital discharge dataset to completely and accurately identify marijuana-related hospitalizations, 2) investigate the association of marijuana-related hospitalizations in Washington State with major marijuana policy changes, 3) measure the association of Washington Poison Center (WAPC) call volume regarding marijuana exposures with key changes in marijuana policy, and 4) describe marijuana exposures occurring among young children after retail sales of marijuana were established in Washington State. METHODS: Data for these analyses were obtained from three sources: 1) Washington State Trauma Registry (WSTR), 2) Comprehensive Hospital Abstract Reporting System (CHARS), and 3) WAPC toxiCALL records. For Aim 1, validity measures for marijuana-related diagnosis codes identified in CHARS were calculated using toxicology screening results available in WSTR as the gold standard for measuring marijuana involvement. For Aim 2, logistic regression was conducted to evaluate the association between experiencing a marijuana-related hospitalization and key changes in marijuana-related policies. For Aim 3, an interrupted time-series analysis was completed to assess changes in the volume of calls to the WAPC for marijuana exposures in relation to important marijuana policy changes. For Aim 4, WAPC records for all children <12 years of age who were reported to have had an exposure to marijuana in 2016 were reviewed to describe exposure details, clinical impacts of exposure, and identify potential avenues for prevention of pediatric exposures. RESULTS: Marijuana-related ICD-CM diagnosis codes are highly specific for identifying marijuana-related hospitalizations, but likely lack sensitivity to detect all hospitalizations in which marijuana is an underlying or contributing factor to hospitalization. The odds of experiencing a marijuana-related hospitalization in Washington State and the volume of marijuana exposure calls to WAPC were both significantly associated with changes in marijuana policy, including the Ogden Memorandum (October 2009), legalization of marijuana for recreational purposes (November 2012), and retail sale of marijuana for recreational purposes (July 2014). The largest associations between marijuana policy changes and marijuana-related hospitalizations were observed among older adults (50+ years). Regarding calls to WAPC, the largest increases in the volume of reported marijuana exposures were observed among very young children (<5 years) and older adults (50+ years). Edible marijuana products were observed to be the largest contributor to reported marijuana exposures, especially among young children. CONCLUSIONS: Liberalization of marijuana policies is associated with increases in adverse health effects, despite efforts to reduce unintentional exposures and adverse effects. The impacts of these policy changes are not evenly distributed across populations, with young children and older adults being disproportionately affected. To reduce the adverse impacts of marijuana policy changes on these populations, a multi-faceted approach including education and legislation will likely be required.
- Epidemiology