Public health researchers look at rise in marijuana-related hospitalizations

Age, gender, and other factors predict risk.

The prevalence of marijuana use in the U.S. more than doubled between 2001 and 2013, according to a study published in October 2015 by JAMA Psychiatry. Hospital utilization related to the drug appears to have increased in tandem, according to a new analysis, presented at the American Public Health Association's annual meeting, held in Chicago in November.

Both marijuana-related hospitalizations and ED visits have increased substantially in recent years, reported He Zhu, PhD, who, with her mentor Li-Tzy Wu, ScD, researched hospital visits related to use of marijuana and other substances.

After a decrease in hospitalizations related to marijuana alone from 2004 to 2007, these inpatient admissions ballooned from 11,267 in 2007 to 20,471 in 2011—an 82% increase, said Dr. Zhu, a postdoctoral associate at Duke University Medical Center in Durham, N.C.

“The use of cannabis has been found to be associated with adverse physical and mental health outcomes in both the short term and the long term,” said Dr. Zhu, noting that it can be linked to drug use disorder, anxiety, psychotic symptoms, breathing problems, increased heart rate, impaired driving, and an increased risk of other substance abuse. “Thus, the increase of cannabis use and its adverse health effects will potentially place more burden on health care systems.”

She expressed concerns about marijuana legalization, as more than 20 states have legalized medical marijuana, and 3 states have made recreational marijuana legal. “This…may potentially contribute to more cannabis consumption in the future,” Dr. Zhu said.

Their analysis focused on patients ages 12 and older who were seen in an ED from 2004 to 2011. The researchers defined “marijuana-related” as any ED visit where use of marijuana was implicated either as a direct cause or contributing factor of the visit, Dr. Zhu said.

Data were obtained from the Drug Abuse Warning Network, a nationally representative surveillance system of drug-related ED visits. Outcomes of hospital utilization were categorized as ED treated and released, inpatient admission, and other dispositions.

This analysis considered 4 categories of marijuana use: marijuana only; marijuana and alcohol; marijuana and other illicit drugs; and marijuana, other illicit drugs, and alcohol. “Our preliminary findings indicated that both the number of cannabis-related ED visits and hospitalizations has increased since 2007, especially for visits involving cannabis use only,” Dr. Zhu said. Marijuana-related ED visits increased by 71% from 2004 to 2011, from 280,671 to 478,989, she reported. Those related to use of marijuana alone increased faster than other categories, reaching 144,566 in 2011, double the number of visits in 2004.

Analysis of the data detected some demographic differences. The majority of marijuana-related ED admissions in the study were among non-Hispanic white men between the ages of 21 and 44, and admissions commonly involved a combination of marijuana and at least 1 other drug, Dr. Zhu said.

ED admissions that involved marijuana only were more likely to be young adults, and ED admissions that involved marijuana and other drugs were more likely to be middle-aged and older adults, she said. Marijuana-only users ages 30 to 44 had 2.3 times the odds of hospitalization instead of being treated and released compared to users younger than 21, and those ages 21 to 29 also had higher odds of hospitalization than users younger than 21, Dr. Zhu said.

Use of marijuana with other drugs increased the likelihood of hospitalization versus being treated and released by 42% compared to marijuana use only, she said. Compared to marijuana-only hospitalizations, women made up a higher proportion of the hospitalizations for marijuana and other illicit drugs, and a higher proportion of Hispanic people combined marijuana and alcohol compared with other ethnic groups.

“Our study expands the literature that suggests an association between health services utilization and cannabis use,” Dr. Zhu said, noting some potential explanations. In general, illicit drug use can contribute to health services utilization, with previous estimates stating that patients who use illicit drugs are 1.3 times more likely to be admitted to the ED than those who don't, she said. Dr. Zhu also noted that recent increases in marijuana's tetrahydrocannabinol content, the psychoactive component of the cannabis plant, may also be related to the uptick.

She noted limitations to the study, such as how hospitalizations were only counted if patients were admitted to the same hospital where they were treated in the ED, which could result in an underestimation of the number of inpatient admissions related to marijuana. Dr. Zhu also pointed out that some details on case types were lacking, as most outcomes were classified as “other dispositions.” Further studies should improve on these data, she said.