legalization of cannabis doesn't lead to abuse of other drugs

and legal weed may actually help with some alcohol-related disorders.

by dave yasvinski

published jan 30, 2023

last updated feb 20, 2023

3 minute read

join the conversation

3 minute read

join the conversation

many of the harmful effects of legal cannabis haven't materialized

there was no change in illicit drug use following the legalization of marijuana. getty

a new study has found that the legalization of recreational cannabis does not increase substance abuse disorders among adults or open up a gateway to other illicit drugs. the research, published in the journal psychological medicine, found no relationship between marijuana legalization and increases in some of the harms often attributed to the drug, including financial, cognitive, psychological, social or relationship problems. although researchers found no evidence the drug had a positive effect on psychosocial health either, they determined it may reduce some of the problems associated with alcohol use.

“we really didn’t find any support for a lot of the harms people worry about with legalization,” said stephanie zellers, lead author of the study who began the research as a graduate student at the university of colorado boulder’s institute for behavioral genetics (ibg). “from a public health perspective, these results are reassuring.”

the research included more than 4,000 twins, now between the ages of 24 and 49, who have been followed since adolescence by a pair of national studies. by comparing the 240 pairs of siblings with one twin living in colorado (which legalized recreational marijuana in 2014) and the other living in minnesota (where the drug remains illegal for recreational use), researchers hoped to get an unfettered view of the health impacts of legalization.

“this co-twin design automatically controls for a wide range of variables, including age, social background, early home life and even genetic inheritance” that can influence health outcomes, said john hewitt, professor of psychology and neuroscience at cu boulder. “if the association holds up, it provides strong evidence that the environment, in this case legalization, is having an impact.”

with previous research on identical twins revealing that those who lived in states with legal access to the drug used it 20 per cent more often, the team hoped to parse out any potential problems associated with use. this included comparing surveys from twins that evaluated 23 measures of “psychosocial distress,” including the use of alcohol and illicit drugs (such as heroin or cocaine), psychotic behaviour, financial or cognitive problems, unemployment and interpersonal relationships.

“we included everything we had data on with the goal of getting a well-rounded look at the impacts on the whole person,” zellers said. “big picture, there’s not much there.”

in addition to finding no relationship between the legalization of marijuana and an increased risk of cannabis use disorder or addiction, researchers found no evidence the substance acted as a gateway to more harmful drugs. there was no change in illicit drug use following the legalization of marijuana.

“for low-level cannabis use, which was the majority of users, in adults, legalization does not appear to increase the risk of substance use disorders,” said christian hopfer, co-author of the study and a medical doctor and professor of psychiatry at ibg and cu anschutz who studies substance abuse disorders.

on the contrary, they found that twins living in states with legalized marijuana displayed fewer symptoms of alcohol use disorder and were less likely to engage in risky behaviour — such as driving under the influence — after drinking.

“our study suggests that we should not be overly concerned about everyday adult use in a legalized environment, but no drug is risk-free,” hewitt said. “it would be a mistake to dismiss the risks from higher doses of a drug that is relatively safe in small amounts.”

although the study had a few limitations, including a failure to examine the health impacts of the drug on adolescents or examine the types and doses of cannabis used, the team hopes its results will help inform public policy and general discussion on the merits of legalization.

“i would love for us to get past this question of, ‘is legalization good or bad?’ and move toward more specific questions like, ‘who is most at risk? who can benefit the most? and how?’ so that people can make informed choices,” zellers said.