The scientific statement is an expert analysis of research that may help inform future clinical practice guidelines for the use of marijuana.
There is scientific evidence that challenges the harmlessness of cannabis and leads to many unanswered questions about its impact on brain health, according to a statement by the American Heart Association (AHA) published in Stroke.
The scientific statement, which is an expert analysis of research, was presented during a symposium at the association’s International Stoke Conference and may inform future clinical practice guidelines.
"There's a lot of uncertainty in the medical community about the health effects of marijuana. This scientific statement is intended to guide health care professionals in having a balanced and intentional discussion with patients about the potential known and unknown effects of marijuana on brain health," Fernando Testai, MD, PhD, FAHA, a professor of neurology and rehabilitation at the University of Illinois at Chicago, said in a statement.
This is the AHA’s first scientific statement on brain health and cannabis, which follows a statement about the cardiovascular health and marijuana published in August 2020.
The most studied forms of cannabis are tetrahydrocannabinol (THC), which is the psychoactive component of cannabis, and cannabidiol (CBD), which has antioxidant and anti-inflammatory properties without the psychoactive effects.
The potential therapeutic benefits of CBD continue to be investigated in clinical trials.
The FDA and US Drug Enforcement Administration classify cannabis as a Schedule I controlled substance, which is grouped with heroin and LSD, for having a high potential for abuse and has little or no medical benefits.
Alternatively, CBD is legally derived from hemp and contains less than 0.3% of THC, according to the statement.
The body naturally produces compounds called endocannabinoids, which are similar to those in marijuana. Endocannabinoids are involved in the regulation of many body processes throughout life, including learning, memory, pain control, and sleep, and are essential to prenatal brain development and maturation during adolescence.
Endocannabinoids, as well as THC, can attach to neurons in the brain through molecules called cannabinoid receptors.
When THC activate cannabinoid receptors in the brain, it can disrupt the normal actions of endocannabinoids, which are highly present in brain areas related to cognition, according to Testai.
Previous animal studies in rodents indicate that prolonged exposure to THC disrupts learning and memory and affects brain development and maturation in specific ways when exposed at certain stages in life, according to the statement.
During prenatal life, THC disrupts the normal signaling pathways of the endocannabinoid systems and may alter emotional behavior, response to stress, and thinking.
Additionally, during adolescence, THC changes the function and structure of brain circuits in areas involving cognition, emotional regulation, and social behavior.
Although the exact timing and amount of marijuana exposure can be controlled in animal studies, as well as environment and social conditions, human research studies cannot replicate strict parameters, according to the statement
Therefore, results from existing studies in humans have been mixed.
Findings in human studies have shown that individuals demonstrated worse scores on driving road tests when using THC-dominant marijuana compared with CBS-dominant marijuana or no marijuana at all, according to the statement.
Additionally, scores on verbal memory tests declined in correlation to more years of self-reported exposure to marijuana in young adults who were studied as part of a 25-year heart disease research project. More psychological problems and poorer cognitive functions were reported in children whose mothers reported using marijuana during pregnancy.
Structural changes in the brain were visible in some studies comparing marijuana users and non-users, specifically, decreased volume in an area of the brain important for memory or thinning in brain areas important in orchestrating actions and thoughts.
However, other studies found no difference in brain imaging and cognitive testing in marijuana non-users and users.
Furthermore, cannabis users were found to have an increased risk of clot-caused strokes, according to the statement.
The statement also highlights numerous questions on the impact of cannabis on brain health, including how cannabis affects the brain depending on an individual’s age, how it could interact with other medications, and how the effects could differ when prescribed for the treatment of specific medical conditions or used recreationally.
"Our understanding of the effects of marijuana on the brain is imperfect, and human research in this area is a work in progress. Still, the results of recent animal studies challenge the widely accepted idea that cannabinoids are harmless and call for caution when using marijuana, particularly while pregnant or during adolescence," Testai said.
How does cannabis use affect brain health? Caution advised, more research needed, experts say. Science Daily. News release. February 10, 2022. Accessed February 16, 2022. https://www.sciencedaily.com/releases/2022/02/220210084937.htm