Marijuana Addiction Could Be Genetic: Study

A person’s likelihood of becoming dependent on marijuana could be up to their genetics, according to a new study.

Researchers from Yale University, in New Haven, Connecticut, found that across racial groups, some specific genetic lines are more likely to report marijuana abuse. The findings also associate a genetic predisposition to marijuana use as related to people who are more likely to develop schizophrenia.

Daniel Levey, M.D., co-author of the study and neurologist at Yale, told Nature that the findings show that use of the drug “could have substantial public health risks if the usage increases.”

“Recently, cannabis use has been legalized in various U.S. states and elsewhere without fully examining the health consequences of individual or societal risks,” researchers wrote in the study. “An epidemiologic survey conducted by the National Survey on Drug Use and Health in the United States identified a past-year cannabis use prevalence of 17.5%, an increase from 11.0% in 2002.”

For the study, published Monday in Nature Genetics, researchers gathered data from more than 1 million people from the Million Veteran Program, a repository of data collected from U.S. military members. The data included nearly 900,000 people of European ancestry, with the remaining data split between people of African, East Asian or American ancestry.

Using genetic correlation, where researchers identify which specific differences people with a certain trait have in their DNA that differ them from others, scientists identified the genetic profiles of people with cannabis use disorder.

Researchers found 22 genes in people of European ancestry, two in people of African and East Asian descent and one in people from the Americas linked to cannabis use disorder. In the European group, the genes were also linked to an increased risk of developing lung cancer. The schizophrenia risk was consistent for all ethnic groups.

Marta Di Forti, Ph.D., told Nature that halting use of cannabis was the easiest way to prevent the development of schizophrenia.

Marijuana use is quickly growing in the U.S. and around the world. While casual use of the drug is not believed to be particularly harmful — on par with other substances such as alcohol — increased research is finding how many people are dependent on the drug, and the harms of overuse of it.

The Centers for Disease Control and Prevention (CDC) cites a study that estimates that 30% of people who use marijuana are dependent on it, with young people at a greater risk.

“The risk of developing marijuana use disorder is greater in people who start using marijuana during youth or adolescence and who use marijuana more frequently,” the CDC writes.

The drug is legal for recreational purposes in 24 states and the District of Columbia, with that list set to grow in the coming years. Advocates have long argued that the drug is relatively harmless and its widespread use would have limited downsides to society.