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.”

Also known as riboflavin, vitamin B2 cannot be produced by the body and must come from food sources such as dairy products, eggs, meat, and green vegetables. Once absorbed, the vitamin is converted into molecules that help protect cells from oxidative damage and support other important biological functions.

Scientists at the Rudolf Virchow Centre (RVZ) at Julius-Maximilians-Universität Würzburg (JMU) have now discovered that this protective effect may come with a serious drawback. Their findings show that vitamin B2 metabolism can also shield cancer cells from destruction.

“Vitamin B2 plays a crucial role in protecting cancer cells from ferroptosis, a special form of programmed cell death,” says PhD student Vera Skafar. She is part of the research team led by José Pedro Friedmann Angeli, Professor of Translational Cell Biology. The study was published in Nature Cell Biology.

How Vitamin B2 Helps Cancer Cells Survive

Programmed cell death is one of the body’s natural defense systems. It allows damaged or dangerous cells to die in a controlled way without triggering inflammation in nearby tissue. Ferroptosis is one type of this process and has been linked to cancer, neurodegenerative diseases, and other serious conditions.

Ferroptosis occurs when iron-driven damage to cell membranes overwhelms a cell’s antioxidant defenses. Cancer cells often avoid this fate by strengthening systems that protect them from oxidative stress.

The new study found that vitamin B2 metabolism plays an important role in these protective defenses. According to the researchers, this means that blocking riboflavin-related pathways could make tumors more vulnerable to ferroptosis and easier to destroy.

Researchers Test a Possible Cancer Therapy Strategy

A protein called FSP1 was central to the team’s investigation. The protein helps healthy cells avoid unwanted cell death, and vitamin B2 supports its activity.

Using genome editing and cancer cell models, the researchers found that cancer cells became much more sensitive to ferroptosis when vitamin B2 was limited.

The team believes this process could eventually be used as a cancer treatment by shutting down vitamin B2 metabolism in tumors and triggering cancer cell death. However, there is currently no inhibitor specifically designed for that purpose.

To explore the idea further, the researchers tested roseoflavin, a naturally occurring compound produced by bacteria that has a structure similar to vitamin B2.

Roseoflavin Successfully Triggered Ferroptosis

In laboratory experiments using cancer cell models, the researchers found that roseoflavin was able to trigger ferroptosis even at low concentrations.

“It turned out that roseoflavin triggers ferroptosis in low concentrations,” says the group leader, “our experiments show the feasibility of this concept.”

The findings suggest that targeting vitamin B2 metabolism could become a promising new approach for future cancer therapies based on ferroptosis.

Next, the RVZ research team plans to develop more effective inhibitors of vitamin B2 metabolism and test them in preclinical cancer models.

Potential Implications Beyond Cancer

Friedmann Angeli says the importance of ferroptosis extends beyond oncology.

“Ferroptosis is not only relevant to cancer. Increasing evidence suggests that it also contributes to pathological processes in neurodegenerative diseases and in tissue damage following organ transplantation or ischemia-reperfusion injury.”

Because of this, understanding how vitamin B2 metabolism influences ferroptosis could eventually help scientists better understand a wide range of diseases involving excessive or insufficient cell death.

The research was supported by the German Research Foundation (DFG) through the priority program “Ferroptosis: from Molecular Basics to Clinical applications” (SPP2306).

The work was also conducted as part of the DeciFerr (Deciphering and exploiting ferroptosis regulatory mechanism in cancer) project led by Professor Friedmann Angeli. Since May 2024, the project has received funding from the European Research Council (ERC) through an ERC Consolidator Grant worth nearly two million euros.

Tinnitus can range from mildly irritating to severely distressing. For some people, the nonstop noise creates anxiety and disrupts daily life. Researchers estimate that as many as 14% of people globally experience the condition, with many cases considered severe.

A team from Oregon Health & Science University and Anhui University in China studied mice and found that increasing serotonin levels in the brain also increased behaviors associated with tinnitus.

Serotonin and Tinnitus Connection

The findings could have important implications for people living with tinnitus, especially those taking antidepressants that affect serotonin levels, said co-senior author Laurence Trussell, Ph.D., professor of otolaryngology in the OHSU School of Medicine and a scientist at the OHSU Vollum Institute and Oregon Hearing Research Center.

“People with tinnitus should work with their prescribing physician to find a drug regimen that gives them a balance between relief of psychiatric symptoms like depression and anxiety, while minimizing the experience of tinnitus,” Trussell said. “This study highlights the importance of clinicians recognizing and validating patient reports of medication-associated increases in tinnitus.”

The medications discussed in the study include selective serotonin reuptake inhibitors, commonly known as SSRIs. These antidepressants are widely prescribed for moderate to severe depression and anxiety because they raise serotonin levels in the brain.

Researchers have long suspected serotonin played a role in tinnitus, but the exact mechanism remained unclear.

“We’ve suspected that serotonin was involved in tinnitus, but we didn’t really understand how,” said co-author Zheng-Quan Tang, Ph.D., of Anhui University in China. “Now, using mice, we’ve found a specific brain circuit involving serotonin that goes straight to the auditory system, and found that it can induce tinnitus-like effects. When we turned that circuit off, we were able to ameliorate the tinnitus significantly.

“This gives us a much clearer picture of what’s going on in the brain — and points toward new possibilities for treatment.”

Tang began the project while working as a postdoctoral scholar in Trussell’s laboratory.

Brain Circuit Linked to Ringing Ears

The new work builds on earlier research published in 2017.

In the latest study, scientists used optogenetics, a technique that uses fiber optics and light to activate specific brain cells. By targeting neurons that produce serotonin, the researchers were able to trigger activity in regions of the brain involved in hearing. They then measured how the mice responded using a modified auditory startle test.

“When you stimulate these serotonergic neurons, we can see that it stimulates activity in the auditory region in the brain,” Trussell said. “We also saw that animals then behaved as if they were hearing tinnitus. In other words, it’s producing symptoms that we would expect to be experienced as tinnitus in humans.”

According to the researchers, the findings match reports from some patients who say their tinnitus becomes more intense while taking serotonin-boosting medications such as SSRIs.

Future Tinnitus Treatments

“Our study suggests a delicate balance,” Trussell said. “It may be possible to develop cell- or brain region-specific drugs that steer the elevation of serotonin in some brain regions but not others. In that way, it may be possible to separate the beneficial and important effects of the antidepressant from the potentially harmful effects on hearing.”

Trussell’s research was supported by the National Institutes of Health through award RO1DC004450. The authors noted that the findings and conclusions are solely their responsibility and do not necessarily reflect the official views of the NIH.