A new large-scale study led by the University of California at San Diego details genetic links to cannabis use with mental and physical traits like obesity, schizophrenia, bipolar disorder and impulsive behavior. The study, which was recently published in the scientific journal Molecular Psychiatry, revealed that lifelong cannabis use is connected to two genes, Cell Adhesion Molecule 2 (CADM2), and Metabotropic Glutamate Receptor 3 (GRM3).
Both genes have previously been cited with brain signaling and impulsivity. Prior research of GRM3 in particular, has also associated the gene with schizophrenia and bipolar disorder. But their connection to cannabis use is a novel finding from researchers at UCSD. Sandra Sanchez-Roige, Ph.D., the senior author of the study, noted that while cannabis use remains prevalent amongst adults, little is truly known about its long-term effects, and creates an urgency for understanding the substance entirely.
“We showed that the genetics of cannabis use — both trying it and using it more often — are tied to the genetics of other psychiatric traits, cognitive measures and even physical health problems,” Sanchez-Roige said in an interview.
Cannabis use disorder, which is classified as a problematic use of cannabis that can range from mild to severe, is also not entirely understood. According to the study’s co-author, Abraham A. Palmer, Ph.D., genetic links between addiction and drug use have long been acknowledged. Researchers of this study hoped to garner a deeper understanding on genetic traits and the development of cannabis use disorder, and potential ways to mitigate the development altogether.
To do so, researchers used a genome-wide association study (GWAS) that sourced its genetic data from 131,895 23andMe participants. Genetic tools like GWAS are instrumental in understanding the links between behaviors and genetics; connecting the dots between cannabis use with brain function and behavior. To assess how prevalent cannabis use amongst each participant, survey questions about cannabis use and frequency were required.
“While most people who try cannabis do not go on to develop cannabis use disorder, some studies estimate that nearly 30% will,” Sanchez-Roige continued. “Understanding the genetics of early-stage behaviors may help clarify who is at greater risk, opening the door to prevention and intervention strategies.”
During a secondary analysis, 40 additional genes were discovered to be associated with a lifetime use of cannabis, and four genes were associated with frequency of using cannabis. 29 of these genes were not known to be associated with cannabis, the study said.
Using independent databases, thousands of traits were analyzed, finding that over 100 different traits, spanning from psychiatric conditions like schizophrenia, ADHD and depression, to cognitive behavior like executive function and risk taking, were “genetically correlated” with a tendency to use cannabis.
Moreover, genetic associations with health conditions like diabetes and chronic pain, and an increased risk of tobacco use and infectious diseases like HIV were also discovered. However, a genetic association does not imply causation, according to the paper. But the findings are still significant and offer important insight into cannabis habits and other health issues.