Is cannabis safe after 65? Stanford experts reveal 5 risks older adults should know

Eloise Theisen never expected to become a specialist in medical cannabis. Now a geriatric nurse practitioner focused on cannabis therapy at Stanford Medicine, she first turned to cannabis herself after a severe car accident left her with chronic pain that other treatments failed to relieve.

When she later returned to work in an oncology clinic, she noticed many patients were already using cannabis or considering it, often without guidance from medical professionals.

"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."

Cannabis Use Is Rising Among Older Adults

Both medical and recreational cannabis use continue to increase across the United States, including among adults over 65. Yet researchers still have major unanswered questions about how cannabis affects the body and brain, partly because marijuana remains federally illegal, making some kinds of research difficult.

Many older adults use cannabis in hopes of easing chronic pain, insomnia, or anxiety. However, Smita Das, MD, PhD, clinical associate professor of psychiatry and behavioral sciences at Stanford Medicine, said there is still no broad medical agreement that cannabis effectively treats these conditions.

Experts say older adults face unique risks from regular cannabis use. These include higher chances of heart disease, certain cancers, addiction, cognitive problems, and dangerous medication interactions. Today's cannabis products are also much stronger than the marijuana many people encountered decades ago, increasing the risk of accidental overuse.

Stanford Medicine specialists shared five important things older adults should know before using cannabis.

1. Today's Cannabis Is Much Stronger Than It Used To Be

Medical marijuana is legal in 40 states and the District of Columbia, while recreational cannabis is legal in 24 states and D.C. Although regular use among seniors remains relatively uncommon, it is rising quickly. According to the National Survey on Drug Use and Health, 7% of adults over 65 reported recent cannabis use in 2023, compared with less than 5% in 2021.

Many older adults may not realize how dramatically cannabis potency has changed. In the 1970s, marijuana typically contained between 1% and 4% tetrahydrocannabinol (THC), the compound responsible for the drug's psychoactive effects. Today, legal cannabis flower averages around 20% THC, and some strains contain as much as 35%.

Other cannabis products can be even more concentrated. Oils, edibles, and concentrates may contain THC levels approaching 90%. Synthetic marijuana products such as spice or K2 are even stronger and have been linked to heart problems. These products are illegal in California and many other states.

"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.

The increased strength of cannabis products may also help explain a rise in accidental overconsumption among older adults. A Canadian study comparing emergency room visits before and after nationwide legalization found that cannabis poisoning cases among adults over 65 nearly tripled.

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

2. Cannabis May Raise Risks for Heart Disease and Cognitive Problems

Although cannabis research is still developing, several studies have linked regular cannabis use to cardiovascular disease.

Joseph Wu, MD, PhD, director of the Stanford Cardiovascular Institute and the Simon H. Stertzer, MD, Professor of Medicine & Radiology, said this is especially concerning for older adults because heart disease remains the leading cause of death in the United States.

Wu's research team found that THC triggers inflammation in blood vessels in animal studies. Epidemiological research has also connected cannabis use with several forms of heart disease in humans. According to these studies, regular cannabis use is associated with a 29% increase in heart attacks and a 20% increase in stroke risk.

While those risks are lower than the risks linked to heavy tobacco or alcohol use, Wu noted that many cannabis users also smoke cigarettes, drink alcohol, or both. Combining these substances may further increase cardiovascular danger. Smoking cannabis has also been associated with lung cancer and cancers of the head and neck.

Wu said smoking and vaping cannabis appear to promote more inflammation than edible products, although edibles are not risk free.

"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."

Theisen also watches for other complications in older patients using cannabis, including dizziness, confusion, falls, and worsening cognitive issues such as dementia.

Older adults metabolize cannabis more slowly than younger people, meaning the drug can stay in the body longer and its effects may last longer than expected. Slower metabolism also increases the chances of interactions with prescription medications.

One example involves cannabidiol (CBD), a non-intoxicating cannabis compound. CBD can interfere with enzymes responsible for breaking down medications such as blood thinners. This may raise drug levels in the body and increase the danger of bleeding after an injury or fall. In some cases, cannabis may also reduce the effectiveness of medications.

3. Cannabis Can Be Addictive

A widespread belief about cannabis is that it is not addictive, but Das said research suggests otherwise.

Studies indicate that roughly 30% of regular cannabis users may develop cannabis use disorder. Like other substance use disorders, the condition is diagnosed based on how strongly the drug affects a person's daily life. Signs may include withdrawal symptoms, needing larger doses over time, or cannabis interfering with relationships and responsibilities.

Even though cannabis addiction rates are lower than those for alcohol, Das said many health care providers may not routinely ask older adults about cannabis use.

"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," Das said. "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."

For people struggling to cut back or quit, Das said speaking openly with a doctor or addiction specialist is important. Treatments such as cognitive behavioral therapy have been shown to help.

"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 also studying how the brain reacts to environmental cues in people with cannabis use disorder and other addictions. Using functional MRI scans, her research has found that people who relapse after treatment often show heightened sensitivity to drug-related signals in their surroundings.

4. Cannabis May Help Some Conditions, but Research Remains Limited

Research suggests that different age groups use cannabis for different reasons.

In a 2017 study led by Padula involving medically licensed cannabis users at a San Francisco dispensary, adults ages 18-30 were more likely to use cannabis for boredom or social situations. Middle-aged users commonly reported insomnia as a reason for use, while adults ages 51-72 often used cannabis for cancer, chronic pain, or other long-term medical conditions.

The Food and Drug Administration has not approved cannabis itself for medical treatment. However, it has approved two cannabis-related compounds for specific uses. CBD is approved for certain forms of childhood epilepsy, while dronabinol, a synthetic cannabis compound, is used to treat nausea and appetite loss in patients with cancer or HIV/AIDS.

Cannabis compounds have also shown benefits for muscle spasms caused by multiple sclerosis. Some countries approve cannabis for that purpose, although the United States does not.

CBD products are now widely marketed for pain, sleep problems, anxiety, and substance use disorders, but evidence supporting many of these uses remains limited.

Research on cannabis for chronic pain has produced mixed findings. Some studies report pain relief, but researchers have also observed large placebo effects. Das helped develop a statement from the American Psychiatric Association opposing cannabis as a psychiatric treatment because there is currently no evidence showing it effectively treats psychiatric disorders.

Theisen sees the issue somewhat differently in her work with palliative care patients facing life-limiting illnesses. Many of these patients use cannabis to manage cancer-related symptoms, including pain, and often want alternatives to opioid medications, which can cause serious side effects and addiction. Research has shown that chronic pain patients who use cannabis sometimes reduce their opioid use.

Theisen also said many patients appreciate the sense of well-being cannabis can provide.

"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. Doctors Say Honest Conversations Matter Most

While experts may disagree about how medically useful cannabis is, they agree on one thing: older adults should talk openly with health care providers before using it.

Theisen said she would rather patients discuss cannabis with a medical professional than rely on advice from dispensary staff or experiment on their own.

During the early years of legalization, she frequently heard stories of patients accidentally consuming extremely high doses of THC edibles because they did not receive proper instructions.

"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.

Reliable information about cannabis can still be difficult to find. Doctors can help patients evaluate whether cannabis is appropriate, discuss possible alternatives, and identify risks related to existing medical conditions or medications.

"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."