Regular cannabis use poses risks to those over 65, experts caution

As more people explore marijuana for medical use, Stanford Medicine scientists warn that older adults should be particularly mindful of potential health concerns.

Geriatric nurse practitioner with a specialty in cannabis therapy at Stanford Medicine, Eloise Theisen, turned to cannabis when nothing else was working for chronic pain resulting from a serious car accident more than a decade ago. Once she was back to work at an oncology clinic, she saw a need with her patients as well—many kept asking her about medical uses of marijuana, and, at the time, little professional advice was available.

“I found that our patients were going to use it whether their providers approved of it or not,” Theisen said. “Many of our patients were older, and they had risks that needed to be evaluated and addressed before they started using cannabis.”

Medical and recreational cannabis use continues to rise in the U.S., including among older adults. But major gaps remain in the scientific understanding of how the drug affects our health. That’s in part because marijuana is still illegal at the federal level, so certain types of research are more complicated.

Many older adults turn to cannabis for chronic pain, insomnia, and anxiety, but there is no medical consensus that it can help for these conditions, said Smita Das, MD, Ph.D., clinical associate professor of psychiatry and behavioral sciences.

For those over 65, there are certain physical and mental risks to regular cannabis use, Stanford Medicine experts warn. These include increased risk of heart disease and certain cancers, as well as the possibility of addiction and exacerbation of age-related cognitive issues. Cannabis can also interfere with certain medications. And, finally, legal cannabis is much stronger than the street pot of decades ago, meaning accidental over-consumption is more likely.

Stanford psychiatrist and addiction medicine specialist Smita Das, MD, Ph.D., MPH, discusses how overconsumption of cannabis can lead to a variety of health problems for older adults.

1. With the strength of today’s cannabis, overconsumption is a risk

Medical cannabis is now legal in 40 states and the District of Columbia; recreational marijuana is legal in 24 and D.C. Although regular cannabis use is still uncommon in older adults, data from the National Survey on Drug Use and Health found that 7% of those over 65 reported recent use in 2023, up from less than 5% in 2021.

Those who came of age before legal cannabis might not realize how different the products are now from what was sold illegally several decades ago. Marijuana in the 1970s contained between 1% and 4% tetrahydrocannabinol, or THC, the psychoactive component of the plant. Today’s legal cannabis flower contains, on average, 20% THC, with some strains as high as 35%. Oils or edibles can have concentrations up to 90%.

Other formulations such as concentrates, oils, or edibles can have concentrations up to 90%. Synthetic marijuana, also known as spice or K2, mimics the psychoactive properties of THC, only with much stronger effects. These manufactured formulations are illegal in California and many other states, and studies have linked their use to heart problems.

“We’re trying to catch up in our understanding of how that drastic of an increase in the psychoactive ingredient is impacting the brain and the body,” said Claudia Padula, Ph.D., assistant professor of psychiatry and behavioral sciences.

Perhaps because of the strength of legal cannabis, accidental over-consumption in older adults is also increasing. A study conducted in Canada before and after marijuana was legalized across the country found a near-tripling of emergency room visits due to cannabis poisoning in those over 65.

“There are so many different formulations and so many different strengths,” Das said. “This is really not the cannabis of the ’70s.”

2. Health risks include heart disease, cognitive issues

Although many aspects of cannabis’s health effects remain understudied, recent research has shown that its use is linked to heart disease. That’s a risk older adults should be aware of, said Joseph Wu, MD, Ph.D., director of the Stanford Cardiovascular Institute and the Simon H. Stertzer, MD, Professor of Medicine & Radiology. Heart disease is the leading cause of death in the U.S. overall, which is largely driven by the high rate of heart disease in those over 65.

Wu and his team found that THC causes blood vessel inflammation in animal models, and his group and others have found links between cannabis use and several types of heart disease in humans in epidemiological studies. These studies found that regular cannabis use is correlated with a 29% increase in heart attacks and a 20% increase in stroke.

The effects are lower than those associated with regular tobacco or excessive alcohol consumption, but those who use cannabis often also use tobacco, alcohol, or both, Wu said. The effects of combining two or three of these drugs appear to be synergistic with heart disease risk. Cannabis smoking is also linked to an increased risk of lung, head and neck cancers.

Smoking and vaping cannabis promote more inflammation than ingesting it, Wu said, but edibles aren’t harmless.

“There is no safe amount of cannabis. Low doses and occasional use are still associated with vascular inflammation,” he said. “Abstinence is the safest option for heart health.”

Besides looping in a patient’s cardiologist if they have known heart conditions, Theisen also keeps an eye on other health effects of cannabis on her older patients. These can include a higher risk of falls due to confusion or dizziness, effects on cognition that might exacerbate age-related cognitive declines like dementia, and interactions with other medications.

Older adults have slower metabolisms than younger people do, meaning it takes longer for them to clear cannabis compounds out of their bodies. Their slower metabolism means that highs can last longer, potentially impairing the user for longer than they expect, and that there are more possibilities for interactions with users’ other medications.

For example, cannabidiol, or CBD, is a non-intoxicating compound found in cannabis that interferes with the enzymes that break down other drugs like blood thinners. This can raise blood thinner levels in the body, which is potentially dangerous if someone has a fall or is otherwise injured. In other cases, cannabis might reduce medications’ effects.

3. The notion that it’s ‘not addictive’ is a myth

One of the most common misconceptions about cannabis: it’s not addictive. In fact, Das said, studies are finding that around 30% of regular cannabis users have what is known as cannabis use disorder. Like other addictions, it is diagnosed based on how the substance affects a person’s life.

Do they experience physical withdrawal symptoms if they stop using? Do they need to use higher and higher doses to get the same effect? Does cannabis get in the way of their daily lives and relationships?

Although rates of cannabis use disorder are lower than those for alcohol use disorder, health care providers may not always be asking the right questions to uncover problems.

“I’m noticing that older adults may not necessarily be disclosing cannabis use to their providers unless specifically asked. This isn’t a population we traditionally think about in terms of using cannabis,” said Das, who specializes in addiction psychiatry. “If someone comes to me for another reason such as depression or alcohol use disorder, I might be the first person who has asked them about their cannabis use.”

And for those who suspect they have a disorder or are having trouble reducing their cannabis use, talking to their providers or a specialist can be key, Das said. As with other substance use disorders, there are proven treatments for cannabis addiction such as cognitive behavioral therapy.

“Empowering individuals by helping them understand the criteria of a substance use disorder can then help them decide, ‘Is this something I want to talk about?'” Das said. “On the clinician side, we can do a lot to make substance use part of the conversation. What are they using the cannabis for? And if somebody wants to stop using, we need to stick with them through the difficult part of stopping.”

Padula is conducting studies on how the brain responds to its surroundings in people who have cannabis use disorder or other substance use disorders. Using functional MRI, which shows which regions of the brain are active, she found that people in treatment for their disorders who go on to relapse are more likely to have hypersensitivity to drug-related cues in their environment.

4. Research is limited, but cannabis can help for certain conditions

In 2017, Padula and her colleagues published a study looking at the motivations for cannabis use among medically licensed customers at a San Francisco dispensary.

They found that users 18–30 were more likely to report using out of boredom or for social interactions, middle-aged adults were most likely to use because of insomnia, and older adults aged 51–72 reported using it for cancer, chronic pain, or other chronic conditions.

The Food and Drug Administration has not approved cannabis for any medical use, but it has approved two cannabinoids, or cannabis compounds, for certain conditions. CBD is approved for some forms of childhood epilepsy; dronabinol is a synthetic cannabis compound that is approved to combat nausea and lack of appetite for patients with cancer or HIV/AIDS.

Cannabis compounds have also been shown to help with spasms caused by multiple sclerosis; it’s approved for that use in some countries but not in the U.S. CBD is also commonly used on its own as a supplement, marketed for pain, sleep, anxiety, substance use disorders, and much more—but studies on its effectiveness for medical purposes other than epilepsy are limited.

While many cannabis users seek relief for chronic pain, research has produced mixed results. One analysis found that while several studies showed a reduction of chronic pain with cannabis use, those studies also had a large placebo effect.

Das helped craft a statement with the American Psychiatric Association opposing the use of cannabis as medicine, in part because there is no evidence that it can effectively treat any psychiatric disorder.

In her current role at Stanford Medicine, Theisen works with older adults through the palliative care department, where she sees patients with life-limiting diseases.

Perhaps in part because of the population she serves, she has a different perspective on the utility of cannabis. Many of them use the drug for cancer-related side effects, she said, including pain. They often want to avoid opioid medications, which can be highly addictive and cause significant side effects—research has shown that chronic pain patients who use cannabis often decrease their use of opioids. And many of Theisen’s patients enjoy how they feel on it, she said.

“THC has gotten a bad rap over the years, but in very small doses it can be therapeutic,” she said. “There’s also a lot of stigma around its effects of euphoria. In our patients who may have months to a few years to live, still being able to experience joy is really important.”

5. The best advice: Talk openly with your health care provider

Although experts don’t always agree on whether cannabis is medically useful, they do agree that adults who are consuming or considering taking it up should discuss it with their medical providers. Theisen would much prefer her patients talk to her or another provider about cannabis than get advice from someone behind the counter at a dispensary or try to go it alone.

In the early days of cannabis legalization, she heard many anecdotes from patients who accidentally took a whopping dose of THC they were sold in edible form with no instructions as to its use.

“Patients would sometimes end up in the emergency department, or they would not want to take it again because they thought, ‘This isn’t going to work for me,'” she said.

Finding trusted sources of information on cannabis can be difficult. If someone is considering it for medical purposes, their doctor can also help assess whether there are other treatments they could try instead. And providers will have insight into possible counter-indications.

“Your primary care physician will know the constellation of your medical conditions and other medications you might be on,” Padula said. “Talking to your doctor and letting them know not only what you’re prescribed, but what you’re using recreationally, will help formulate a way to do it in as safe a manner as possible.”