It's long been the argument of law enforcement and anti-medical marijuana advocates that the government-sanctioned pot dispensaries cause an uptick in crime, especially burglary and muggings. The only problem is that argument isn't necessarily true, according to a new study funded by the National Institutes of Health.

On its face, the argument makes sense—medical marijuana dispensaries feature large caches of high quality drugs, and its customers overwhelmingly walk in with a huge wad of cash and walk out with a desirable product. But the study, published in the Journal of Studies on Alcohol and Drugs, found that neighborhoods with medical marijuana dispensaries in Sacramento were no more likely to have crime than other neighborhoods.

The study's authors say their research may debunk a 2009 report by the California Police Chiefs Association that said marijuana dispensaries "have been tied to organized criminal gangs, foster large [marijuana growth] operations, and are often multi-million-dollar profit centers."

"Because they are repositories of valuable marijuana crops and large amounts of cash, several operators of dispensaries have been attacked and murdered by armed robbers both at their storefronts and homes, and such places have been regularly burglarized," the report continues. "Drug dealing, sales to minors, loitering, heavy vehicle and foot traffic in retail areas, increased noise, and robberies of customers just outside dispensaries are also common ancillary by-products of their operations."

Arguments such as those are common by opponents of medical marijuana legalization, which will soon be available in as many as 17 states and the District of Columbia.

"There's law enforcement and city officials debating whether these dispensaries were attracting undesirables, and there's the other side, the dispensary owners, saying maybe these concerns were unfounded," says co-author Nancy Kepple, a doctoral student at the UCLA Luskin School of Public Affairs. "But neither side had any evidence that supported either claim."

The UCLA study looked at crime rates in 95 areas of Sacramento in 2009, before the city enacted regulations on where dispensaries could be located and had fewer restrictions on what security measures dispensary operators had to meet.

"Whatever security measures were done, the owners chose to do it for themselves [in 2009]. We specifically selected this time because it was based on a free-market situation," says Kepple.

Although the researchers aren't sure why there was no uptick in crime around dispensaries, they suspect that security guards and cameras have an impact on keeping criminals out. Or, as Kepple wrote in the report, it could be that marijuana dispensaries just don't increase crime any "more than any other facility in a commercially-zoned area."

Several high-profile murders in San Francisco and Hollywood dispensaries and burglaries in San Francisco, Santa Cruz, and Colorado Springs have made dispensary-based crime national news, but those cases aren't representative of a larger trend, Kepple and her co-author, Bridget Freisthler, say.

"Because of the type of business dispensaries are, any crime there has been well-publicized, bringing more attention to the issue," Freisthler says. "Neighborhood residents get up in arms and it takes a life of its own." She says pot dispensaries appear to be no more likely to be victimized by burglars than liquor stores or other commercial spots.

Still, the authors realize there are potential holes in their study. They say they need to study crime rates in other cities and need to study crime trends over time to determine whether dispensaries have long-term impacts on neighborhood crime.

"This is really just the start, and [our findings] seem contrary to what the public debate has been saying," Kepple says. "We wanted to start thinking about the debate from a scientific standpoint."