Scientists have long ago debunked the myth that using marijuana kills brain cells.
One of the most popular myths about cannabis is that using it can kill brain cells and lead to brain damage.
This belief dates back to anti-drug campaigns in the 70s and 80s, which spread the idea that marijuana could permanently damage the brain.
But nowadays, doctors and health professionals know this simply isn’t true.
“It’s just people who, unfortunately, aren’t well-educated on it who continue to propagate that false myth,” says Michael Verbora, MD, a physician who regularly prescribes medical marijuana in his role at Toronto’s Cannabinoid Medical Clinic.
Many still compare marijuana to recreational drugs such as alcohol and tobacco, which have indeed been shown to cause brain damage in long-term users. But interesting enough, marijuana does not appear to pose the same threat.
Permanent Effects on the Brain
Many studies over the decades have investigated the effects of marijuana use on the brain. Overall, these studies have failed to identify any permanent changes in the brains of long-term marijuana users.
“Every study shows that it just doesn’t kill brain cells,” says Dr. Perry Solomon, a retired anesthesiologist and chief medical officer at HelloMD.com.
In 2003, researchers at the University of California, San Diego compiled the findings of 15 previous studies on marijuana and cognitive function. After analyzing results from over 1,000 test subjects, the researchers concluded that marijuana users may suffer from minor impairments in learning and memory, but the effects were only temporary.
Similarly, a 2015 study by researchers at the University of Colorado Boulder looked at brain imaging scans of marijuana users verses non-users. They found that marijuana users did not suffer from any physical changes in major areas of the brain.
Temporary Effects on the Brain
While research has conclusively shown that marijuana use does not lead to permanent brain damage, there is evidence of temporary impairments in those who use the drug.
Specifically, marijuana is known to interfere with specific aspects of memory and learning. However, this effect only lasts for a short duration of time.
“We do know that temporarily using cannabis does work in areas of the brain that are involved in memory and learning… but it’s completely reversible once the drug wears off,” explains Dr. Verbora.
This was demonstrated in 2001 by researchers at Harvard University, who looked at the cognitive performance of marijuana users before and after quitting.
The participants were asked to complete a set of intelligence, attention, learning and memory tests during a period of sustained abstinence. The results showed that heavy users of marijuana scored significantly lower in memory tests during the first week after quitting.
However, their scores returned to normal levels within 28 days, leading the researchers to conclude that even heavy use of marijuana “produces no irreversible mental deficits.”
Positive Effects on the Brain
Contrary to the belief that marijuana poses a threat to a user’s brain, there is significant evidence that marijuana has positive long-term effects on the brain, especially when it comes to its use as a medicine.
In fact, many studies suggest that cannabinoids — the active compounds in marijuana — could be useful in treating a variety of degenerative brain disorders, including Alzheimer’s and Parkinson’s disease.
“The U.S. government does hold a patent on the antioxidant and neuroprotective effects of cannabinoids,” says Dr. Verbora. “If you read through the patent, they believe that cannabinoids actually might help with brain damage.”
Indeed, studies have found that cannabinoids possess antioxidant and neuroprotective properties, suggesting that cannabis may in fact work to protect brain cells rather than harm them.
Risks for Adolescent Users
While it’s clear that adult marijuana users are not likely to suffer from brain damage, experts remain wary about adolescent users. During adolescence, the brain is still undergoing stages of development, making it more susceptible to the negative effects of drugs.
“I think when the brain’s developing and growing and maturing that there could be effects to [using marijuana],” says Dr. Solomon.
On the other hand, any negative impact of marijuana on the developing brain has yet to be quantified.
For example, in a landmark study published in 2016, researchers from UCLA and the University of Minnesota analyzed the results of two separate twin studies, which included data from over 3,000 participants, and found no link between marijuana use during adolescence and a drop in IQ.
The results were in direct contrast with the findings of a 2012 study by New Zealand researchers that suggested a link between heavy marijuana use beginning in adolescence and a decline in IQ later in life.
Risks of Smoking
Although research shows that using marijuana does not kill brain cells, how people consume marijuana may put them at greater risk.
Smoking happens to be the most common way of consuming marijuana. But experts warn that this could be an issue when it comes to keeping your brain healthy.
“It’s the fact that when you smoke for temporary periods of time, your brain loses oxygen in some areas and, under a microscope, there could be some cellular damage,” explains Dr. Verbora.
To minimize this risk, health professionals often recommend the use of a vaporizer for anyone who prefers to inhale cannabis. Another popular option is ingesting marijuana in the form of edibles, which can provide a longer duration of action as well as protect the brain and lungs from possible harm.