Thinking About Marijuana After 65? Doctors Warn of Overlooked Health Risks

Many people are using marijuana for medical reasons, and it may provide benefits for some. However, Stanford Medicine experts warn that older adults, in particular, should be mindful of the potential health risks.

Eloise Theisen had no plans to become a medical cannabis expert.

Now a geriatric nurse practitioner who specializes in cannabis therapy at Stanford Medicine, Theisen first turned to cannabis herself after other treatments failed to control chronic pain caused by a serious car accident more than ten years ago. When she later returned to work at an oncology clinic, she began to notice a similar issue among her patients. Many of them were asking about the medical use of marijuana, yet reliable professional guidance was scarce at the time.

“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.”

Across the United States, both medical and recreational cannabis use continues to increase, including among older adults. At the same time, significant gaps remain in scientific knowledge about how marijuana affects health. One reason is that cannabis remains illegal at the federal level, which makes certain types of research difficult to conduct. Many older adults use cannabis to manage chronic pain, insomnia, or anxiety, but there is no clear medical agreement that it is effective for these conditions, said Smita Das, MD, PhD, a clinical associate professor of psychiatry and behavioral sciences.

Stanford Medicine experts caution that regular cannabis use carries specific risks for people over 65. These include a higher likelihood of heart disease and certain cancers, along with the potential for addiction and worsening of age-related cognitive problems. Cannabis can also interact with prescription medications. In addition, legal cannabis products today are far more potent than those commonly available decades ago, which increases the risk of accidental overconsumption.

To clarify these issues, Theisen, Das, and other Stanford Medicine specialists were asked to address common questions about cannabis use in older adults. What health risks should they consider? What options exist for those who want to stop using cannabis but find it difficult? Based on their expertise, they outline five key points that potential users should understand.

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

Medical cannabis is now legal in 40 states and the District of Columbia, while recreational marijuana is legal in 24 states and D.C. Although routine cannabis use remains less common among older adults, data from the National Survey on Drug Use and Health show that 7 percent of people over 65 reported recent use in 2023, up from fewer than 5 percent in 2021.

Older adults who grew up before legalization may not realize how much cannabis products have changed. In the 1970s, marijuana typically contained between 1 percent and 4 percent tetrahydrocannabinol, or THC, the compound responsible for its psychoactive effects. Today, legal cannabis flower averages about 20 percent THC, with some strains reaching as high as 35 percent.

Other products, including concentrates, oils, and edibles, can contain THC levels of up to 90 percent. Synthetic marijuana, often called spice or K2, is designed to mimic the effects of THC but can be far more powerful. These manufactured substances are illegal in California and many other states, and research has linked their use to serious 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, PhD, 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.”

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, PhD, 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 appears to be synergistic on heart disease risk. Cannabis smoking is also linked to increased risk of lung and 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 do younger people, meaning it takes longer for them to clear cannabis compounds out of their bodies. Their slower metabolism means both 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.

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’s 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.

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 it 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.”

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.”

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