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As many U.S. states slowly begin to relax their grip on marijuana prohibition, researchers are increasingly able to access cannabis and explore its medical benefits and risks. A new study in the Journal of Neuroscience is exploring one of these potential risks, identifying a "potential unifying mechanism whereby marijuana could exert rewarding and addictive/withdrawal effects" on juvenile and adolescent cannabis users.
Researchers from Brigham Young University in Utah conducted a series of experiments to see how THC affects the brains of juvenile and adolescent mice. The researchers focused on the ventral tegmental area (VTA) of the brain, which contains receptors for two important brain chemicals, dopamine and gamma-Aminobutyric acid (GABA). These two neurotransmitters interact with the brain's motivational system, which rewards behaviors like eating or having sex by making these activities feel pleasurable.
The researchers gave the young mice one injection of THC every day for 7 to 10 consecutive days, discovering that these injections altered the synaptic plasticity of the mice's VTA cells and decreased their ability to strengthen or weaken in response to changes in brain activity. Dr. Jeffery Edwards, lead author of the study, explained to Medical News Today that "all psychoactive substances that alter synaptic plasticity [...] of VTA dopamine cells, even once the drug is out of the system, are addictive, while non-addictive psychoactive substances do not alter plasticity."
Because the VTA is involved with motivation and reward, any disruption to that system could lead to addictive behavior. "It is important to note that these studies were carried out in juvenile/adolescent aged mice," Dr. Edwards said. "This is important as adolescent humans have worse THC-induced outcomes compared to adults. Adolescents who use THC have decreased IQ, decreased cognition, and increased change of further drug abuse with other drugs."
Dr. Edwards hopes to expand upon this research by examining "if this plasticity occurs in adults, and if so whether THC can alter this plasticity as well." If THC does not alter this plasticity in adults, "it would implicate this site in mediating some of the negative outcomes of cannabis use disorder or increased substance abuse that occurs in adolescents that does not occur in adults." This could lead to further research that could help understand or treat addictive tendencies in adolescents or even adults.
This research underlines the importance of scientific inquiries into cannabis, identifying some of the potential risks that may need to be considered by physicians who wish to recommend medical cannabis to adolescents. The federal prohibition of marijuana has made research like this extremely difficult, however, and legislative attempts to remove these restrictions are still facing an uphill battle in Congress.