While some young men try marijuana but don’t continue to use it long-term, others usually develop a pot problem that lasts into adulthood. A major new analysis shows that at least a small fraction of the risk of developing into an adult marijuana user may be related to the inherited behaviors and traits that emerge during adolescence.
the magazine addicted He published the findings of researchers at Brown University and Emory University.
“Our analysis suggests that some early adolescent behaviors and traits – such as depression, neuroticism and acting – could be indicative of cannabis use later in life,” says Rohan Palmer, lead author of the paper and associate professor in the Department of Psychology at Emory. Heads the Behavioral Genetics Lab for Addiction.
“Decades of research have shown that behaviors can have a genetic component,” adds Leslie Brick, lead author and associate professor in the Department of Psychiatry and Human Behavior at the Albert School of Medicine at Brown University. “Although there is not a single genetically influenced trait that determines whether you will use cannabis in the long term, our research paper indicates that there are polygenic effects across many inherited behaviors and traits that show a tendency to increase risk.”
Brick, a longtime Rohan collaborator, also holds an assistant faculty appointment in the Psychology Department at Emory.
The Transmissible Liability Index is a known measure of a set of genetic traits that may appear during growth years associated with the risk of developing a substance use disorder. For the current paper, the researchers wanted to discover which of these heritable characteristics might be related to frequent marijuana use later in life.
“Hemp use has been less studied than tobacco and alcohol,” Palmer says. For one thing, it is difficult to get people to honestly answer detailed questionnaires about cannabis, as it is an illegal substance. It is also much more difficult to standardize the amount of cannabis consumed, compared to cigarettes and alcoholic drinks. “
However, cannabis use is common among teens and young adults. In 2018, more than 35 percent of high school seniors surveyed reported having used marijuana within the past year and more than 20 percent reported using marijuana within the past month, according to the National Institute of Drug Abuse (NIDA).
As cultural norms shift, including the legalization of marijuana for adult recreational use in several states, teens’ perceptions of the dangers of marijuana use have diminished.
However, these risks are real.
“Adolescence is a key period in brain development,” says Brick. “In fact, our brains don’t stop developing until around the age of 25. Research indicates that cannabis has some major effects on our biology, although its full effects are still not well understood.”
The researchers extracted data from the National Longitudinal Study of Adolescent Health, or Health Addition, which includes a nationally representative sample of 20,000 adolescents in grades 7 through 12 in the United States who were followed into adulthood. Comprehensive data were collected from early adolescence through adulthood on healthy and health-related behavior, including substance abuse, personality and genetics.
For the current paper, the researchers identified a large homogeneous subset of individuals from the Add Health study, approximately 5,000 individuals of European descent, for a final analytical sample. They then leveraged genome-wide association studies to examine whether some of the inherited behavioral traits observed during adolescence were associated with an index of transmissible liability, and whether any of these traits were also associated with the risk of later cannabis use.
The results showed that a small fraction of the risk of frequent cannabis use in adulthood could be attributed to the genetic effects of neuroticism, risk tolerance and depression that can appear during adolescence.
“While this work represents an important step in identifying genetic factors that can increase the risk of cannabis use, a large portion of the factors that increase risk are still not justified,” Palmer says. “We have shown how you can use current data to assess the utility of a polygenic risk score. Further studies are needed to further identify the unique genetic and other environmental sources of risk for long-term use and problems of cannabis.”
“A better understanding of the behaviors and traits that might give someone a predisposition to using cannabis in the long term gives us a better chance to identify those most at risk so we can effectively intervene,” says Brick
The researchers add that one of the main limitations of the current study is that it focused on individuals of European ancestry, because there was not a large enough sample size for large-scale genome analysis of other ancestral groups.
Study co-authors include the following members of Emory’s Behavioral Genetics of Addiction Lab: graduate students Lauren Bertine, Kathleen Martin, and former student Victoria Reisner (now almost Emory); And Chelsie Benca-Bachman, Associate Director of Research Projects at the laboratory.
The work was supported by an Avenir grant from the National Institute of Drug Abuse.
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