Another rift in the quest toward federal marijuana legalization is being investigated, as a research team from the University of Pittsburgh Graduate School of Public Health found a link between the growing number of medical marijuana dispensaries and increased marijuana-related hospitalizations. Whether this link establishes true causality remains to be seen, but researchers are insisting that greater insight into the topic is necessary to prevent future health issues for the public. The study will be published in the Sept. 1 issue of the journal Drug and Alcohol Dependence.

In light of this new evidence, researchers are asking the public to reexamine legalization related to both medical and recreational use of marijuana. The study, funded by the National Institutes of Health, is the first to look at the impact of the number of marijuana dispensaries statewide, while also analyzing the characteristics of a population in relation to their marijuana-related hospitalizations.

Lead author and assistant professor in Pitt Public Health Department, Dr. Christina Mair says looking into where medical marijuana dispensaries are placed and the subsequent health outcomes on the public is key to discovering the degree of risk. “Our study indicates that there are real problems associated with a higher density of marijuana dispensaries in neighborhoods,” she said in a recent press release. “More study and monitoring, coupled with thoughtful legislation and community decision will be prudent to ensure that marijuana laws have the fewest negative consequences for vulnerable populations.”

The team decided to investigate California, the state with the longest standing medical marijuana program in the United States, established in 1996 with the Compassionate Use Act. Since the legislation, medical marijuana dispensaries are popping up more and more to meet the growing demand and expanding program. To analyze health outcomes on the surrounding population, researchers used studies on liquor stores as a guide. Previous research on liquor stores measured how the density of these places within a given population could possibly affect health outcome. Researchers say that policymakers, as well as health care practitioners could also learn from these studies about how to minimize health repercussions in a similar fashion.

For the study, researchers looked at California hospital discharges between the years 2001 and 2012 that had either a primary or secondary code related to marijuana dependence, or abuse. Overall, the team observed an increase during this time, finding 17,469 marijuana-related hospitalizations in 2001 grew to 68,408 hospitalizations in 2012. Interestingly, an overwhelming 85 percent of these cases were related to marijuana abuse as opposed to dependence. When asked what this distinction meant, Mair told Medical Daily that abuse constitutes “continued, frequent use despite negative consequences (including emotional, missing school/work, social consequences, some physical manifestations of problems),” while dependence was more of a physical addiction, or “what we often picture when we think of ‘drug addiction.’”

Also, 99.2 percent, almost all of the cases, were secondary codes, meaning that the primary reason a patient was hospitalized was not marijuana. Mair gave an example of a secondary code, saying "So if they were, say, a cancer patient using medical MJ they’d be unlikely to receive a secondary code for abuse, but if they had an accident (e.g., unintentional injury) they might get a secondary diagnosis code. Once again, I personally don’t give these codes."

What’s more, when researchers examined ZIP codes of hospitalized patients in relation to number of dispensaries in that area, they found that with every dispensary within a square mile of a given ZIP code, there was a 6.8 increase in the number of hospitalizations linked to marijuana.

As far as the demographic of those living in these regions, Mair says that people living in lower income neighborhoods with lower education levels were more likely to wind up in the hospital in some way or another, with marijuana somehow involved.

Even though this research is definitely something to think about, Mair concedes that they are not sure if the link means that these dispensaries are causing the hospitalizations. In fact, the study does state that within some states, usage of marijuana was higher before legalization, while others found that legalization brought no change in the frequency of use. “It is unclear if the marijuana dispensaries are simply located in neighborhoods that tend to be more disadvantaged and already have underlying problems with marijuana abuse, or if presence of the dispensaries is causing an increase in abuse and hospitalizations,” she said. “It could be both factors.”

Because greater numbers of dispensaries did show a trend toward increased hospitalizations, but these hospitalizations often involved marijuana in an indirect, often remote way, further research must be done in order to determine causality. As for now, researchers say proceed with caution: Though we cannot fully ascertain if the dispensaries are at fault, researchers suggest we are better safe than sorry.

"Passage of laws permitting marijuana use and sale is likely to continue, so it is critical that we continue to research the impact of dispensaries on the health of local communities to provide guidance on regulations and public health outreach to prevent abuse," Mair said.

Source: Mair C, Freisthler B, Ponicki W, et al. The impacts of marijuana dispensary density and neighborhood ecology on marijuana abuse and dependence. Drug and Alcohol Dependence. 2015.