Conventional wisdom says marijuana dispensaries make neighborhoods less safe, but a new study from UC Irvine suggests the conventional wisdom is wrong and that crime increases after cities move to close pot shops.

“Given all the pretty strong rhetoric about dispensaries generating or at least attracting crime, it was not the result we expected,” said Mireille Jacobson, a health economics professor at UCI who studied the data with colleague Tom Chang. “But I feel comfortable saying it’s very unlikely that these places are crime magnets.”

Dispensaries seem to behave in this respect much like restaurants and other mainstream businesses, Jacobson said, helping to deter vehicle break-ins and other low-level crimes simply by putting more bystanders on the streets.

The study was intentionally narrow in its focus, examining the impact of widespread closures that took place on a single day in Los Angeles. So it couldn’t account for violent crimes such as murder or arson, according to Jacobson, since they aren’t common enough to show up in the window of time she and Chang analyzed.

The study also didn’t attempt to factor in how marijuana dispensaries might impact local quality of life – either for the better, by offering alternatives to addictive drugs such as opiates, or for the negative, by increasing problems such as loitering and traffic.

Future research on those areas is crucial before broad conclusions on how cannabis shops impact crime can be locked down, the report states.

But Jacobson hopes her study might lead to more fact-based policy discussions as California gets ready to launch recreational marijuana sales on Jan. 1.

The study

Inspiration for the study goes back to 2010. Jacobson was living in Venice and noticed that dispensaries all over town were being shut down as Los Angeles attempted to rein in its massive medical marijuana market.

The talk at the time was largely about how these stores made neighborhoods less safe, with reports by the Los Angeles Police Department that blamed crime rate increases in the mid-2000s on the city’s explosion of pot shops.

Even today, while 90 percent of Americans support people’s right to use medical marijuana, the same polls show 44 percent said they would be “somewhat or very concerned” if a dispensary opened near them.

Only one city in Orange County allows medical marijuana dispensaries, while just a handful of cities permit such shops in Riverside and San Bernardino counties. And many law enforcement agencies and policymakers cite public safety concerns when explaining their opposition to allowing marijuana activities in their boundaries.

“This town has been a town of safety. And we’re trying with this initiative to make sure that we keep our residents safe,” said Fontana Mayor Acquanetta Warren just before she helped vote in one of the most restrictive cannabis policies in the state.

Jacobson had never studied the marijuana industry before 2010. But given how tough it is both to pinpoint definite causes for changes in crime rates and to study then-unregulated dispensaries, she saw the scenario that was unfolding in L.A. as the perfect test for a simple premise.

“If these dispensaries truly were crime magnets, we’d expect to see a sharp decrease in crime when they shut down,” Jacobson said.

On June 7, 2010, roughly 70 percent of the nearly 600 shops operating in Los Angeles were ordered to close.

Jacobson and Chang used data collected by the Los Angeles Times to analyze crime rates before and after shops shut down, comparing those numbers to neighborhoods where shops were allowed to stay open. Though they looked at 60 days of data, Jacobson said they limited their main focus to a 20-day window because many of the closures were temporary. Once it became clear that the city wasn’t going to enforce its ban, dispensaries started to randomly reopen.

The professors found a 12 to 14 percent increase in property crimes within a third of a mile surrounding the shuttered pot shops. At a fourth of a mile out, they study found a 14 to 16 percent increase in crime. And at an eighth of a mile, the study found a 23 to 24 percent increase in low-level crimes once dispensaries were shut down.

Based on those numbers, the study says one open dispensary might save the neighborhood more than $30,000 each year by preventing petty thefts.

The Los Angeles Police Department said they hadn’t had a chance to review the UC Irvine study and so couldn’t comment on its findings. And a spokesman for the department’s union, the Los Angeles Police Protective League, declined to weigh in on how these results jive with what their officers see in the field.

The explanation

Jacobson and Change wanted to better understand what caused the spike in crime after dispensaries shut down. So they analyzed the same data on another type of business that faces similar circumstances.

When restaurants are temporarily shut down due to health code violations, the study found nearly identical increases in low-level crimes as what they saw in connection to dispensaries. The pattern suggests that it’s not pot shops in particular that help deter crime, but just about any type of business that brings more people to a neighborhood.

It’s known as the “eyes upon the street” theory, framed in a 1961 book by urban activist Jane Jacobs. The idea is that streets are safer when more people are around to keep an eye on what’s happening.

Related: Legalizing medical marijuana has little impact on crime – except in California, study says

Dispensaries may have some added cushions against increased crime, the study says. They tend to have security cameras and security guards on their property. They may draw more regular police patrols. And there’s data to show that marijuana use might reduce aggressive behavior.

Though dispensaries sell a unique product, Jacobson said mounting evidence suggests policymakers can safely regulate them much as they do other small businesses.

“It seems to me that we don’t report on the crime at Starbucks or 7-Eleven or other businesses in the same way that we report on crime around dispensaries because people are interested in that,” she said. “It’s fine to talk about how you need to regulate dispensaries, but you don’t need to throw these scare tactics out there.”