With interest in marijuana use growing, it’s important to know both the pros and the cons that are supported by peer-reviewed research. Here’s what the science community has to say (so far) about marijuana’s effects on the heart and the brain.
Marijuana and Memory Loss?
Researchers have long suggested marijuana can cause memory loss. Now, a new study provides insight into this association, revealing how cannabinoids in the drug activate receptors in the mitochondria of the brain’s memory center to cause amnesia.
Study leader Dr. Giovanni Marsicano, of the University of Bordeaux in France, and team believe their findings – published in the journal Nature – may lead to the development of new therapeutics that target cannabinoid receptors, without the side effect of memory loss.
Cannabinoids are chemicals present in marijuana, as well as synthetic forms of the drug.
These cannabinoids are similar in structure to cannabinoids that occur in the body naturally, such as anandamide. Naturally occurring cannabinoids function as neurotransmitters; they send signals between nerve cells, or neurons, affecting various brain regions, including those responsible for emotion, movement, coordination, sensory perception, and memory and thinking.
Because THC and other cannabinoids present in marijuana and synthetic forms are similar to naturally occurring cannabinoids, they can bind to cannabinoid receptors situated on neurons and activate certain brain regions.
As a result, cannabinoids can alter normal brain functioning, causing some negative mental and physical effects. One such effect may be memory loss; researchers have shown that THC can affect the function of the hippocampus – the brain region responsible for forming memories.
In the new study, Dr. Marsicano and team further explored the relationship between cannabinoids and memory loss.
CB1 Cannabinoid Receptors In Mitochondria Regulate Memory Processes
In recent years, researchers discovered that one cannabinoid receptor called CB1 is located in the mitochondria of nerve cells. Mitochondria are referred to as the “powerhouses” of cells, as they convert the sugar, fat, and proteins we get from food into energy that cells need to function.
For their study, Dr. Marsicano and colleagues used a variety of innovative methods to find that there are CB1 receptors within the mitochondria of hippocampal neurons, and cannabinoids activate these to cause memory loss.
On further investigation, the researchers found that the memory loss triggered by cannabinoids is down to direct activation of CB1 receptors in the mitochondria, which alters mitochondrial activity. CB1 activation blocks the cannabinoid signaling cascade within mitochondria, and it also reduces cellular respiration – a process that enables the conversion of nutrients into energy.
In simple terms, the study shows that CB1 cannabinoid receptors in mitochondria control memory processes by adjusting the energy metabolism of mitochondria.
Confirming their findings, the team discovered that genetically eliminating the CB1 receptor from mitochondria in the hippocampus prevents memory loss. It also reduces the movement of mitochondria and the inhibition of neuronal signaling caused by cannabinoids.
‘Selective Intervention’ on CB1 Receptors May Lead To New Therapeutics
Cannabinoids have shown potential benefits for some health conditions, including pain, nausea and vomiting, and neurological disorders. However, the researchers note that the use of therapeutic cannabinoids has been hampered by the side effects they present, such as memory loss.
Dr. Marsicano and team believe their findings could fuel the development of new, safer therapies that target cannabinoid receptors.
“[…] a selective intervention on specific CB1 cannabinoid receptors located in the brain in certain specific neurone compartments could be of interest with a view to developing new therapeutic tools based on the most effective and safest cannabinoids in the treatment of certain brain diseases.”
Study co-author Dr. Pedro Grandes, the University of the Basque Country, Spain
Marijuana and Heart Problems?
In the United States, marijuana is the most commonly used illegal drug (illegal in most states, that is). While the effects of marijuana on the cardiovascular system remain largely unknown, a new study suggests that marijuana use may double the risk of stress cardiomyopathy, a condition where the heart muscles are quickly and severely weakened.
Smoking marijuana may lead to heart problems.
According to the Centers for Disease Control and Prevention (CDC), in 2013, 19.8 million Americans aged 12 years or older reported having used marijuana in the preceding month.
In 2014, that number had increased at a rate of approximately 7,000 new users every day.
More and more people perceive the use of marijuana as completely harmless. Between 2002-2014, the CDC report that the perceived risk of marijuana decreased, while the number of individuals who perceived marijuana as risk-free increased.
But a new study suggests there may be a link between the use of marijuana and an uncommon heart muscle malfunction.
What is Stress Cardiomyopathy?
Stress cardiomyopathy is popularly referred to as “broken heart syndrome” because it can be caused by extreme emotional stressors, such as grief, fear, surprise, and anger.
The condition can also be caused by physical stressors, such as stroke, seizure, breathing difficulties, or heavy bleeding.
According to the Johns Hopkins Heart and Vascular Institute, the symptoms of stress cardiomyopathy are very similar to those of a heart attack, and they include chest pain, shortness of breath, dizziness, and palpitations. This is due to the heart’s temporary inability to pump blood.
However, unlike a heart attack, stress cardiomyopathy does not kill any heart cells; instead, it temporarily stuns them using adrenaline and other hormones. As a result, recovery from broken heart syndrome is quick and leaves no permanent damage.
Dr. Amitoj Singh, chief cardiology fellow at St. Luke’s University Health Network in Bethlehem, PA, led a study where he examined the link between stress cardiomyopathy and marijuana use.
The results of the research were presented at the American Heart Association’s Scientific Sessions 2016 in New Orleans, LA.
Marijuana Use May Double The Risk Of Stress Cardiomyopathy
Researchers looked at 33,343 people who were admitted to the hospital with stress cardiomyopathy between 2003-2011. The data was taken from the Nationwide Inpatient Sample.
Of these patients, 210 – less than 1 percent – were also marijuana users. Active marijuana use was established either from the information provided by the patient, or by testing for markers in the patient’s urine.
Marijuana users were more than twice as likely to develop stress cardiomyopathy than nonusers.
However, even after adjusting for the already low cardiovascular risk factors, marijuana users were more likely to go into cardiac arrest during stress cardiomyopathy than nonusers.
Marijuana users had a 2.4 percent risk of going into cardiac arrest, compared with the 0.8 percent risk in nonusers.
Marijuana users were also more likely to require an implanted defibrillator to stabilize dangerously abnormal heart rhythms, with a 2.4 percent likelihood, compared with 0.6 percent in nonusers.
Researchers also adjusted for other risk factors that are normally associated with stress cardiomyopathy, as well as factors cannabis users were far more likely to have.
These included a higher likelihood of depression, (32.9 percent compared with 14.5 percent in nonusers), tobacco use (73.3 percent compared with 28.6 percent in nonusers), psychosis (11.9 percent versus 3.8 percent in nonusers), and anxiety disorder (28.4 percent likelihood compared with 16.2 percent in nonusers).
Further Research Needed To Confirm Causality
“This development of stress cardiomyopathy in younger patients who used marijuana suggests a possible link that needs to be further investigated,” says Dr. Sahil Agrawal, co-author of the study and chief cardiology fellow at St. Luke’s.
As this is an observational study, however, it cannot establish causality. Therefore we cannot say whether marijuana directly causes stress cardiomyopathy. But if users experience heart problems, the authors warn, they should see a doctor.
“If you are using marijuana and develop symptoms such as chest pain and shortness of breath, you should be evaluated by a healthcare provider to make sure you aren’t having stress cardiomyopathy or another heart problem.”
Dr. Amitoj Singh
Researchers did not have access to data from all of the nation’s states, but instead focused on regional reports. As a result, researchers could not establish whether marijuana-related stress cardiomyopathy has a higher incidence rate in those states where recreational use is legal. These may be useful directions for future research.
As Dr. Singh says: “The effects of marijuana, especially on the cardiovascular system, are not well known yet. With its increasing availability and legalization in some states, people need to know that marijuana may be harmful to the heart and blood vessels in some people.”
Finally, scientists were unable to analyze how often participants used marijuana, or how much time had passed between marijuana intake and the occurrence of stress cardiomyopathy.
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