Researchers using the genomes of a million people from various databases have identified genes they believe are linked to cannabis addiction. According to an article in Nature, the researchers said some of the same genome regions are tied to health conditions including lung cancer and schizophrenia.

The study was just published in Nature Genetics.

Dr. Daniel Levey, a medical neuroscientist at Yale and study co-author, told Nature the finding shows that addiction to cannabis is “evidence that cannabis addiction could have substantial public health risks if the usage increases.”

According to Yale News, the research indicates links to “psychiatric disorders, abuse of other substances such as tobacco, and possibly even an elevated risk of developing lung cancer.”

Both the study and the Nature article point out the increasing legality of cannabis for recreational purposes, including in eight countries, and medicinal use in 48 countries. “But one-third of people who take cannabis end up becoming addicted or using the drug in ways that are damaging to their health.”

Earlier research suggests a genetic component in the links between problematic cannabis use and health challenges.

The data the researchers used came primarily from the U.S. Department of Veterans Affairs’ Million Veteran Program, a massive genetic database. They also used several smaller databases. Per Yale News, “They were able to identify dozens of genetic variants linked to cannabis use disorder and a variety of behavioral and health issues associated with cannabis use disorder.”

According to the Centers for Disease Control and Prevention, 48 million people — nearly 1 in 5 Americans — used marijuana at least one time in 2019. The CDC said recent research estimates that about 30% of people who use marijuana have marijuana use disorder and the risk is highest for those who begin using the drug before age 18.

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“Marijuana use directly affects the brain, specifically the parts of the brain responsible for memory, learning, attention, decision-making, coordination, emotion and reaction time. Infants, children and teens (who still have developing brains) are especially susceptible to the adverse effects of marijuana,” the CDC article said, noting long-term or frequent use increases the risk of psychosis or schizophrenia in some users.

Levey told Nature that the fact marijuana addiction is a product of some combination of genetics and environment makes it hard to study, but the researchers built on earlier work using the databases, including data from many ethnic groups.

Marta DiForti, a psychiatrist-scientist at King’s College London, told Nature that cannabis use “is the most preventable risk factor for schizophrenia.”

Per that article, “More information about the biological mechanisms that connect cannabis use with health conditions will provide a better evidence base for policy and medical practice, says study co-author Joel Gelernter, a psychiatric geneticist at Yale University.”

It’s worth noting that much of the research being done on cannabis and its impact on the brain and on health is being done at Yale, which according to the New Haven Register has recently created the Center for the Science of Cannabis and Cannabinoids.

The researchers said that a better understanding of both the mechanisms of addiction and the potential impact are needed since cannabis use has become so prevalent.