How does cannabis use affect brain health? Caution advised, more
research needed, experts say
American Heart Association Scientific Statement

Date:
February 10, 2022
Source:
American Heart Association
Summary:
Although recreational and medicinal marijuana (cannabis) is
increasingly available across the U.S., public and professional
awareness that cannabis use may adversely affect brain health
is critical, according to the American Heart Association's first
scientific statement on the subject.



FULL STORY ========================================================================== Despite the perception that marijuana is harmless, there is some
scientific evidence challenging that belief, and there are many
unanswered questions about its impact on brain health, according to a
new American Heart Association scientific statement published today
in the Association's journal Stroke. This scientific statement will
be presented and discussed during a symposium at the Association's International Stroke Conference in New Orleans, today at 7 a.m.

CT/ 8 a.m. ET. An American Heart Association scientific statement is
an expert analysis of current research 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," said writing group Chair Fernando D. Testai, M.D.,
Ph.D., FAHA, a professor of neurology and rehabilitation at the University
of Illinois at Chicago.

This is the Association's first scientific statement on cannabis and
brain health, following a statement on marijuana and cardiovascular
health, published in August 2020. Both statements are important since
marijuana use in the U.S.

is increasing, particularly among adolescents and young adults, with
about one- third of 12th graders and nearly half of college students
reporting marijuana use in 2018. In addition, the use of marijuana
medicinally and/or recreationally has been legalized or decriminalized in
many states across the U.S. in the past 2 decades, and the concentration
of tetrahydrocannabinol (THC, the psychoactive component in marijuana)
in cannabis products has increased significantly, from about 4% in 1995
to 15% in 2018.

The most studied chemicals in cannabis are THC and CBD. THC is the
compound in marijuana that gives the sensation of being high. CBD
(cannabidiol) has antioxidant and anti-inflammatory properties but does
not have psychoactive effects. The potential therapeutic benefits of
CBD continue to be investigated in clinical trials.

The U.S. Drug Enforcement Agency (DEA) and the Food and Drug
Administration (FDA) classify cannabis as a Schedule I controlled
substance, on par with heroin and LSD, for having a "high potential for
abuse and little to no medical benefit." In contrast, CBD is legal when
derived from hemp, which is the same species of plant as cannabis and
contains less than 0.3% THC.

To fully understand the potential impact of marijuana, it's important
to know that the human body naturally produces compounds called endocannabinoids that 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 the action
of endocannabinoids is essential to prenatal brain development and to
brain maturation during adolescence.



========================================================================== Endocannabinoids, as well as THC, can attach to neurons in the brain
through molecules called cannabinoid receptors. When THC activates
cannabinoid receptors in the brain, it can disrupt the normal actions
of endocannabinoids.

"These receptors are highly concentrated in brain areas related to
cognition," said Testai.

According to the statement, previous animal studies (in rodents) indicate
that prolonged exposure to THC disrupts memory and learning, and impacts
brain development and maturation in specific ways if exposed at certain
stages of life:
* During prenatal life, an important time for brain development, THC
disrupts the normal signaling pathways of the endocannabinoid
system and may alter the offspring's thinking, emotional behavior
and response to stress.

* During adolescence, an important time for brain maturation,
THC changes
the structure and function of brain circuits, particularly in areas
involved in cognition, emotional regulation and social behavior
(such as the prefrontal cortex and hippocampus).

"Data obtained in these animal studies demonstrate that disruption of endocannabinoid pathways leads to behavioral and cognitive abnormalities,
such as poorer memory and learning ability and a heightened sensitivity
to stress.

Also, there may be vital life periods -- gestation and adolescence --
when the brain may be particularly vulnerable to the impact of THC,"
Testai said.

While the exact timing and amount of marijuana exposure are more easily controlled in animal studies, as well as controlling the animals' social
and environmental conditions, human research studies cannot replicate
similar strict parameters. Thus, results from existing studies in humans
have been mixed, yet raise similar concerns about the impact of marijuana exposure on brain health. Among the studies in humans summarized in the scientific statement, the findings included:
* While actively using marijuana, people demonstrated worse scores on
driving road tests when using THC-dominant marijuana, compared to
when they were using CBD-dominant marijuana or no marijuana.

* In young adults who were followed for 25 years as part of a
heart disease
research project, scores on verbal memory tests declined in
correlation to more years of self-reported exposure to marijuana.

* There were more psychological problems and poorer cognitive
function in
children (average age 9) whose mothers reported using marijuana
during pregnancy.

* Marijuana use during adolescence has been associated with thinning
in an
area of the brain involved in cognition (the prefrontal cortex),
with greater exposure to marijuana associated with more
thinning. However, other studies detected no difference.

* Structural changes in the brain were visible in some studies
comparing
marijuana users and non-users. Specifically, there was thinning
of brain areas important in orchestrating thoughts and actions, or
decreased volume in an area of the brain important for memory. Other
studies that compared cognitive testing and brain imaging found
no differences between marijuana users and non-users.

* Cannabis users were found to have an increased risk of clot-caused
stroke, with one study finding 17% more and another finding 24%
more strokes among cannabis users.

The statement also highlights numerous open questions on the impact of
cannabis on brain health, including:
* Does marijuana's impact on brain health differ depending on the
person's
age?
* How does marijuana interact with other substances such as
prescription
medications? This is a particular concern in elderly people
who may be using multiple medications such as blood thinners,
antiarrhythmia or anticonvulsant medications to treat other chronic
health conditions.

* Do the effects of marijuana differ whether it is used recreationally
or
prescribed for the treatment of a specific medical condition?
* How much marijuana is too much? In older research studies conducted
when
marijuana was illegal in all U.S. states, there may have been
significant under-reporting of how frequently marijuana was used.

* Do different types of marijuana (such as higher THC levels or
synthetic
cannabinoids) impact the brain differently?
* Are there differences in brain health depending on whether
marijuana is
smoked or consumed in an edible product?
"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," said Testai.

This scientific statement was prepared by the volunteer writing group on
behalf of the American Heart Association's Stroke Brain Health Science Subcommittee of the Stroke Council; the Council on Arteriosclerosis,
Thrombosis and Vascular Biology; the Council on Cardiovascular and
Stroke Nursing; the Council on Lifestyle and Cardiometabolic Health;
and the Council on Peripheral Vascular Disease. The American Academy of Neurology has affirmed this scientific statement as an educational tool
for neurologists.

American Heart Association scientific statements promote greater
awareness about cardiovascular diseases and stroke issues and help
facilitate informed health care decisions. Scientific statements
outline what is currently known about a topic and what areas need
additional research. While scientific statements inform the development
of guidelines, they do not make treatment recommendations. American
Heart Association guidelines provide the Association's official clinical practice recommendations.

Co-authors are Philip B. Gorelick, M.D., M.P.H.; Hugo J. Aparicio,
M.D., M.P.H.; Francesca M. Filbey, Ph.D.; Raul Gonzalez, Ph.D.; Rebecca
F. Gottesman, M.D., Ph.D.; Miriam Melis, Ph.D.; Mariann R. Piano,
R.N., Ph.D.; Tiziana Rubino, Ph.D.; and Sarah Y. Song, M.D. Authors' disclosures are listed in the manuscript.

special promotion Explore the latest scientific research on sleep and
dreams in this free online course from New Scientist -- Sign_up_now_>>> ========================================================================== Story Source: Materials provided by American_Heart_Association. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Fernando D. Testai, Philip B. Gorelick, Hugo J. Aparicio,
Francesca M.

Filbey, Raul Gonzalez, Rebecca F. Gottesman, Miriam Melis,
Mariann R.

Piano, Tiziana Rubino, Sarah Y. Song. Use of Marijuana: Effect
on Brain Health: A Scientific Statement From the American Heart
Association.

Stroke, 2022; DOI: 10.1161/STR.0000000000000396 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220210084937.htm

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