A U.S. state’s politics could be influencing how people use cannabis, suggests a new study out Wednesday from Columbia University. It found that liberal states had higher rates of pot use than conservative states, but conservative states had higher rates of harmful, addictive use. These differences could be seen among certain age groups whether a state had legalized the use of pot in any way or not.
Currently, the medical use of cannabis is allowed in 33 states, while 10 states, including Michigan and Vermont in 2018, have legalized it recreationally. Plenty of research has been done to figure out whether this growing legalization of cannabis use has affected its popularity. Most of these studies have found that medical marijuana laws have made it more commonly used by young adults, but not kids and teens (the data is less certain about the effects of recreational cannabis laws on youth rates).
But a state’s pot laws aren’t the only thing that could shape our attitudes and behaviors surrounding the drug, according to lead author Morgan Philbin, a social and behavioral scientist at Columbia University’s Mailman School of Public Health.
“[T]hese state-specific cannabis laws exist within a broader policy context and that relationship had yet to be explored (e.g., a medical cannabis law in Hawaii exists within a very different state specific context than, say Arizona),” she told Gizmodo via email. “Other work (e.g., on LGBT rights and immigration) demonstrated that the policy climate as a whole can impact individual health outcomes and we wanted to explore if this was also the case for cannabis use.”
Philbin and her team turned to data from the State Rank on Policy Liberalism Index, a scale developed by political scientist Virginia Gray. The scale ranks a state’s political leaning based on their policies surrounding topics like gun control, abortion rights, welfare, and labor rights. Two versions of the index have been published, in 2005 and 2011, with states such as New York, New Jersey and California topping the liberal ranks, and states like North Dakota, Alabama, and Mississippi ranked as the most conservative. That data was then cross-referenced with data from the National Survey on Drug Use and Health, which tracks self-reported drug use among different age groups.
Overall, adults over the age of 26 reported using cannabis in the past year the least, while 18- to 25-year-olds used it the most, according to the study. And people in conservative states consistently reported using cannabis less than those living in liberal states—a gap that got bigger over time. Between 2005 to 2011, for instance, the percentage of reported pot use among 18- to 25-year-olds rose from 33 percent to 37 percent in the most liberal states, while it only rose from 25 percent to 26 percent in the most conservative states.
Some of these people used cannabis so often that they fit the bill for cannabis use disorder (CUD). But while the percentage of cannabis use disorder declined across both liberal and conservative states, it overall remained higher in red states. Between 2005 to 2011, for instance, the percentage of CUD among 18- to 25-year-old cannabis users dropped from 22 percent to 18 percent, but also dropped from 20 percent to 17 percent among the same age group in liberal states, according to the survey. The same pattern could be seen with every other age group.
In both cases, the difference in cannabis use and CUD between liberal and conservative states could still be seen even after taking into account a state’s medical marijuana laws, though really only for younger people below the age of 26. That suggests that other important public health policies are affecting our cannabis habits.
But Philbin says there’s an important caveat to their findings, published Wednesday in the International Journal of Drug Policy. Because of the type of data used, the study doesn’t directly show that living in a liberal state causes more cannabis use or less disordered use (or vice-versa, for living in a conservative state).
“What it does show is that policies that are not directly designed to target a specific outcome, in this case cannabis use, still have an impact,” she said. “This may occur because the broader policy climate impacts individual health by changing the context in which other policies operate, or perhaps make other—more healthier behaviors—the default.”
So maybe the healthier the average resident is, the team’s results could suggest, the less likely they could ever suffer from CUD. State laws regulating the use of other available drugs, like alcohol or tobacco, could also affect the likelihood of cannabis use. If nothing else, the study also suggests that even if a state does experience growing rates of cannabis use, that doesn’t necessarily mean more residents will develop a harmful addiction to it—and that there are policies that can prevent this from happening.
“These differing policy contexts may contribute to state-specific differences that need to be taken into consideration when passing cannabis policies in the U.S. (e.g., things like stigma, service availability, care access and cannabis-specific knowledge and attitudes),” Philbin said. “The same holds for cannabis legalization: policies legalizing cannabis may have different impacts on cannabis use depending on the state in which it is passed, and it is important for policy makers to be aware of, and discuss those factors when considering legalization.”
The study is the first to look at the connection between state-wide policy and cannabis use, the authors said. Future research will need to identify what specific polices could be affecting cannabis use, as well as whether these differences between liberal and conservative states can be seen over a longer length of time and more recently, after 2011, and among different demographic groups.
