Scientists discover genetic links between cannabis use and risk of addiction

A new study conducted by researchers at the’University of California, San Diego (UCSD) highlights the genetic factors that may influence consumption from Cannabis or the development of a dependence on this substance.

Posted in Molecular Psychiatry, this study identifies several genetic variants linked to the’impulsivity, to psychiatric disorders and physical characteristics, which helps explain why some people are more vulnerable to cannabis use disorder (CUD).

These results are based on a genome-wide association study (GWAS) large-scale study using data from nearly 132,000 participants of the genetic testing company 23andMe. Participants completed questionnaires to determine whether they had ever used cannabis and how frequently they had used it during their periods of heaviest use. The researchers then analyzed biological and genetic correlations to identify patterns common across all populations.

According to Sandra Sanchez-Roige, an associate professor of psychiatry at UCSD and one of the study’s lead authors, «While most people who try cannabis do not develop a cannabis use disorder, some studies estimate that nearly 30% of them will.».

According to her, understanding the genetic basis of these early behaviors could help identify those most at risk and pave the way for preventive or therapeutic strategies.

Genes that influence behavior and brain function

The UCSD team identified two key genetic regions associated with cannabis use over the course of a person’s lifetime: CADM2 (cell adhesion molecule 2) and GRM3 (metabotropic glutamate receptor 3). These two genes play a key role in communication and the development of neurons in the brain.

CADM2, already known for its role in nerve cell signaling, has been linked to the’impulsivity, at the’obesity and even to the cancer metastases. It has also been shown to influence the frequency of cannabis use, suggesting that the same neural pathways that influence impulsive behavior may also contribute to higher levels of consumption.

GRM3, for its part, regulates communication between neurons and promotes the long-term brain plasticity. Variations in this gene have already been linked to schizophrenia and bipolar disorder, which could explain the overlap in biological mechanisms between cannabis use and certain psychiatric disorders.

«By studying the biological mechanisms that explain why a person might use cannabis and then develop a disorder, we will discover something fundamental that could lead to new treatments,» said Sanchez-Roige.

His colleague, Abraham A. Palmer, said that these organizations do not mean that cannabis causes schizophrenia or other mental illnesses. «It’s simply that certain biological pathways may be common to cannabis and schizophrenia« .

Broader genetic and social implications

Beyond individual genes, the study revealed more than 40 additional genetic variants related to lifetime cannabis use, including 29 had never been linked previously associated with cannabis-related traits. These genetic factors were found to overlap with those associated with substance use, to mood disorders, at the’anxiety and even to physical health indicators such as the characteristics of red blood cells and susceptibility to infectious diseases.

Palmer noted: «We have known for decades that genetic factors influence people’s decisions about whether to try drugs, how often they use them, and their risk of becoming addicted. Genetic tools such as GWAS help us identify the molecular mechanisms that link cannabis use to brain function and behavior.»

However, experts point out that genetics alone does not allow us to predict dependence.

Wayne Kepner, a researcher on substance use disorders at Stanford University who did not participate in the study, explains that addiction is «deeply influenced by context, stress, and the social environment.» He added that no single gene—or even a group of genes—can explain why some people develop an addiction while others do not.