Places with more marijuana dispensaries have more marijuana-related hospitalizations

The National Institutes of Health-funded research, published online and scheduled for the Sept. 1 issue of the scientific journal Drug and Alcohol Dependence, could be informative as more states consider legalizing marijuana for medical and recreational use. It is the first analysis of the statewide impact of marijuana dispensaries on abuse and dependence, as well as the first look at population characteristics associated with marijuana-related hospitalization rates.

"As marijuana is approved for medical or recreational use, we need to carefully consider where we allow dispensaries to be placed," said lead author Christina Mair, Ph.D., assistant professor in Pitt Public Health's Department of Behavioral and Community Health Sciences. "Our study indicates that there are real problems associated with a higher density of marijuana dispensaries in neighborhoods. More study and monitoring, coupled with thoughtful legislation and community discussion, will be prudent to ensure that marijuana laws have the fewest negative consequences for vulnerable populations."

In 1996, California was the first state to legalize medical marijuana, allowing physicians to prescribe the drug for medical purposes. Since then, 22 states and Washington, D.C., have enacted similar laws, and four of those states also have legalized recreational use. Pennsylvania doesn't allow either, though it is considering permitting medical marijuana.

Dr. Mair and her team looked at data on California hospital discharges that had either a primary or secondary medical code for marijuana dependence or abuse with at least one overnight hospital stay. The research covered 2001 through 2012, the most recent years for which consistent data were available.

Hospitalizations with marijuana abuse or dependence codes increased from 17,469 in 2001 to 68,408 in 2012. More than 85 percent of marijuana-related hospitalizations were coded as abuse, rather than dependence, and 99.2 percent were secondary codes, meaning the person was primarily hospitalized for something other than marijuana.

When the research team mapped the location of marijuana dispensaries and cross-referenced it with the ZIP code of each patient's home, they found that each additional dispensary per square mile in a ZIP code was associated with a 6.8 percent increase in the number of hospitalizations linked to marijuana abuse and dependence.

In addition, Dr. Mair and her team found that marijuana dispensaries and hospitalizations were more likely to be located in areas with lower household incomes and lower educational attainment.

"It's unclear if the marijuana dispensaries are simply locating in neighborhoods that tend to be more disadvantaged and already have underlying problems with marijuana abuse, or if the presence of the dispensaries is causing an increase in abuse and hospitalizations," said Dr. Mair. "It could be a combination of both factors."

Dr. Mair noted that research on the location of marijuana dispensaries has a parallel precedent in the location of liquor stores. This gives policymakers and public health practitioners the opportunity to learn from previous studies on the health effects of density and location of liquor stores in order to design studies that can provide similar data on marijuana dispensaries.

"Once dispensaries open, it is much harder to go back and create regulations to guide their location and density," said Dr. Mair. "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."