Researchers Discover Genetic Factors Behind Cannabis Use Patterns

A groundbreaking study has uncovered genetic links to cannabis use, revealing why some individuals use the substance infrequently while others develop patterns of frequent use or even cannabis use disorder. Researchers from the Schulich School of Medicine & Dentistry, including postdoctoral researcher Hayley Thorpe, collaborated with the University of California San Diego School of Medicine to conduct this pioneering research, published in the journal Molecular Psychiatry.

The team analyzed data from over 130,000 individuals to explore the genetic factors influencing cannabis use frequency. They discovered that cannabis use is not determined by a single gene but by a combination of genetic variations. “Our study is specifically focused on the genetics of cannabis use and the relationships these genetics have with health,” Thorpe stated. She emphasized the importance of understanding how individuals engage with cannabis, as it significantly impacts health outcomes.

The study highlights an urgent need for clinical treatments to address cannabis use disorder, which affects up to 27 percent of those who have tried cannabis. Currently, there are no pharmacological treatments available for this disorder. Thorpe hopes that identifying the genetic pathways associated with cannabis use will pave the way for new therapeutic interventions.

Genetic Insights into Cannabis Behavior

Employing a genome-wide association study (GWAS) method, the researchers scanned the entire genome to identify common genetic variants linked to cannabis use traits. They focused on two specific traits: lifetime cannabis use and frequency of use. The team identified genetic variations in two genes, CADM2 and GRM3. Previous studies connected CADM2 to impulsivity and risk-taking behavior, but this is the first time it has been linked to the frequency of cannabis use. Notably, GRM3 had not been previously associated with cannabis use.

Thorpe explained that the lifetime cannabis use trait includes individuals who use cannabis infrequently, possibly only once, and does not represent the genetics of regular users. In contrast, the frequency of use trait encompasses those who may experience the effects of recurrent use. By distinguishing between these stages, researchers could delve deeper into the genetics of pre-addiction behaviors.

“This study is the first to use GWAS to examine any intermediary stages of cannabis use through frequency,” Thorpe noted. She stressed that understanding this trait can provide insights into the biological and health associations of regular, yet non-pathological, cannabis use.

Broader Implications for Public Health

While Thorpe acknowledges that genetics are not the sole determinant of cannabis use patterns, they play a significant role in an individual’s vulnerability to substance use. The research holds potential benefits in two key areas: developing treatments for cannabis use disorder and reducing the stigma surrounding its use.

“When we understand the genetics of cannabis use, we can delve deeper into the biological mechanisms underpinning the effects of its use, which can lead to new therapeutic interventions,” Thorpe explained. She added that genetics also influence how individuals experience drugs, a crucial factor in the development of substance use disorders.

Thorpe cautioned against the misconception that cannabis use inevitably leads to adverse health outcomes. “Our study’s focus was the associations between the genetics of cannabis use and health, not cannabis use itself,” she clarified. Personal experiences with recreational substances like cannabis can vary significantly, underscoring the need to understand the mechanisms at play that are beyond individual control.

Looking forward, Thorpe’s team plans to investigate additional cannabis-related traits, such as the heaviness of use, withdrawal symptoms, and cravings. For Thorpe, this research is not merely about decoding DNA; it aims to foster a greater understanding of cannabis use, which can inform public health initiatives and lead to treatments that improve lives.