A new research study has confirmed evidence that cannabis legalization is linked to decreased rates of alcohol abuse, but does not increase the risk of psychosis or drug abuse.
The new study, published in this month's edition of the Psychological Medicine journal, sourced data from a longitudinal study that tracked 4,043 twins over the course of their lives. Out of this cohort, researchers identified 240 pairs of twins where one twin lived in an adult-use state and the other lived in a prohibition state. Twin studies provide particularly compelling results as they allow researchers to control for genetics, family history, and other factors that could arise when comparing two unrelated people.
The study authors set out to prove or disprove several common “reefer madness” myths that prohibitionists continue to espouse. Namely, researchers investigated whether legal weed would act as a “gateway drug” that would force twins in adult-use states to abuse other drugs. The study also explored whether subjects residing in legal weed states would be more likely to experience symptoms of psychosis than their twins who live in prohibition states.
An analysis of the data clearly indicated that neither of these myths hold up to scientific scrutiny. Researchers did find that twins who lived in adult-use states were in fact more likely to smoke weed than twins who live in states where weed is illegal. However, adult-use state residents were not any more likely to experience psychosis or to abuse other drugs than their twins. In fact, twins living in recreational states were less likely to abuse alcohol than their siblings who reside in prohibition states.
“Recreational cannabis legalization causes increases in mean cannabis frequency and residents of recreational states have fewer recent symptoms of AUD [alcohol use disorder],” the study authors wrote, according to NORML. “Broadly speaking, our co-twin control and differential vulnerability results suggest that the impacts of recreational cannabis legalization on psychiatric and psychosocial outcomes are otherwise minimal… Both sets of results are reassuring with respect to public health concerns around recreational cannabis legalization.”
These findings back up several other recent studies exploring the interactions between legal cannabis, alcohol, and psychosis. Researchers have discovered that college students who live in adult-use states are less likely to binge drink than their peers in other states, and alcohol sales have significantly declined in states where medical marijuana is legal. Other studies have also found that overall interest in alcohol is lower in states where residents have access to legal weed.
Early federally-funded research did identify a correlation between cannabis use and psychosis, but more recent studies have found that this link is likely explained by the fact that people with mental health issues are more likely to seek out pot. Researchers have also confirmed that weed does not increase the risk of psychosis, and that less than half of one percent of all cannabis users have ever experienced a psychotic episode.
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