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Research is still emerging on the effects cannabis use can have on the brain.
Studio Marmellata/Stocksy United
  • The American Heart Association has issued a scientific statement warning about the potential use of cannabis.
  • The organization says frequent use of the drug can impact the developing brains of people under 25.
  • They add cannabis can also impair adults in certain functions such as driving a car.
  • An expert tells Healthline that cannabis has risks just like any other medication and should be used in moderation.

The American Heart Association (AHA) wants people to know a few things about cannabis, namely that it isn’t harmless, especially on young and developing brains.

AHA officials say their first scientific statement regarding cannabis and brain health is being issued to help medical professionals have “balanced and intentional” conversations with their patients.

They say the statement reflects known research on how cannabis can impact things such as a young person’s brain development or an adult’s ability to drive a car.

In recent years, the AHA released statement papers about its viewpoints regarding cannabis and stroke risk and cannabis use and complications with heart attacks. The research involved people who smoked cannabis or didn’t focus on the different outcomes of other ingestion methods, like consuming edibles or tinctures.

Citing studies involving rodents — which it acknowledges isn’t always transferable to humans — the AHA statement says “prolonged exposure” to the psychoactive chemical in cannabis, tetrahydrocannabinol or THC, can impact brain development at younger ages when brain development and maturation is in high gear.

While not entirely groundbreaking by suggesting that pregnant people and young children not consume THC regularly, it does distinguish the different medical impacts of THC versus CBD (cannabidiol), such as treatment for seizures in children.

The statement cites studies which show that THC consumed by a pregnant mother can impact her child’s thinking, emotional behavior, and response to stress.

The statement also says that during the formative adolescent years, THC can change parts of a young brain like the prefrontal cortex and hippocampus, which impact a person’s cognitive abilities, regulation of emotions, and social behavior.

Citing those studies involving rodents, Dr. Fernando D. Testai, a professor of neurology and rehabilitation at the University of Illinois at Chicago and chair of the voluntary group that wrote the AHA’s scientific statement, said in a press release that there’s still plenty of uncertainty in the medical community about the health effects of cannabis, and that the statement’s intention is to help doctors talk with their patients.

“Our understanding of the effects of marijuana on the brain is imperfect and human research in this area is a work in progress,” Testai said.

“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,” he said.

Research on what long-term effects cannabis use can have on the human brain is also largely lacking because the U.S. government classifies cannabis as a schedule 1 controlled substance, saying it has a high risk of misuse with little medical advantages.

The general medical consensus is that heavy cannabis use can have lingering effects on brains less than 25 years old. As for brains in people older than 25, the science is still out.

THC’s ability to impact a young person’s developing mind has prompted some states that have legalized cannabis to people as young as 18 to establish awareness campaigns that switch “don’t” to “delay.” The campaigns are designed to encourage young children to wait until they’re a little older to consume cannabis.

As NPR reported, much of that messaging is around edibles that can look and taste like candy but can pack a high dose wallop if a person consumes too much.

The Centers for Disease Control and Prevention (CDC) has similar warnings about the effects of THC on young and developing brains, including how it can impact attention, memory, and learning.

The THC effects depend on concentration consumed, how regularly the drug is used, at what age people are using, and whether the drugs used with other substances such as alcohol or tobacco.

The CDC and other government agencies have not developed a safe dosing list, similar to what it considers safe and normal for other substances like alcohol.

Dr. Jordan Tishler is president and CEO of inhaleMD, a Massachusetts-based medical cannabis treatment center, and an instructor at Harvard Medical School.

He says much of what the AHA says in its scientific statement is accurate because cannabis, like any other medication, is not without risk.

Tishler, however, says the AHA presents “an anti-cannabis bias” in that the cognitive differences seen in adult cannabis users have not been shown to be persistent, and cannabis use in teens has not been rising, as the AHA states.

“Overall, cannabis is less dangerous than many medications that we use regularly and many substances that are freely available in society. Like all medications, cannabis must be used carefully and judiciously to maximize benefit and minimize risk to the patient,” Tishler told Healthline.

“Cannabis should not be used in pregnancy and during breastfeeding. It must be used with extra care for pediatric and adolescent patients,” he said.