A new study identified specific genes that may make someone more likely to become dependent on marijuana.
Researchers at Yale University examined the genes of nearly 15,000 people to try to determine the relationship between genetics and addiction.
Between 18 percent and 36 percent of participants exhibited a dependency on marijuana, according to TIME. Previous research estimated 10 percent of marijuana users become addicted, but a high amount of marijuana addicts were used for this study to increase the chances of discovering associated genes.
The team found three genetic variations linked to symptoms of marijuana addiction. One of these genetic variants is involved in the regulation of calcium, which plays a role in the formation of addictions to other substances such as opioids, Yahoo! News reports. Genes that regulate calcium are also reportedly linked to the risk of developing schizophrenia, depression, autism and attention-deficit/hyperactivity disorder (ADHD).
Another genetic variant was located in the gene CSMD1, which is involved in the formation of the central nervous system. Other variants of CSMD1 were previously linked to the risk of developing schizophrenia, which has been connected to marijuana addiction.
Previous studies involving marijuana and schizophrenia failed to prove whether marijuana increases the risk of developing the disorder, or if it's simply a common coping tool for people prone to schizophrenia.
As is the case with schizophrenia, a direct causal link between marijuana and depression has never truly been established, but a 2002 study found 90 percent of marijuana addicts were also suffering from another psychological disorder.
This new study reaffirms the link between marijuana and other disorders, as the development of addiction to marijuana appears to involve the same genes that are associated with depression and schizophrenia.
The Yale findings could lead certain youths to undergo genetic testing to see if they have a higher risk of marijuana addiction due to the presence of these genetic variants. Socially disconnected teenagers reportedly possess the highest risk of becoming addicted to any drug, and therefore awareness of risk factors at an early age is extremely important.
This study was originally published in the journal JAMA Psychiatry.