Cannabis and the Aging Brain

The conversation happens almost every week now. A patient in their seventies sits across from me, asking about marijuana for chronic pain, insomnia, or anxiety. Or their adult children call, concerned because mom started using cannabis gummies after a friend recommended them. Sometimes a colleague reaches out, uncertain how to counsel an older patient who insists cannabis is "natural" and therefore safe.

These conversations would have been rare a decade ago. Now they are routine.

Recent epidemiological data reveal that approximately 7% of adults over 65 reported past-month cannabis use in 2023, a 46% increase from just two years prior. Among older adults with two or more chronic diseases, use jumped by 134%. This is not recreational experimentation. This is millions of older Americans self-medicating with a substance that bears almost no resemblance to what they may have tried in their youth.

Whether you are a clinician fielding these questions or a family member trying to make sense of the headlines, this is what the evidence actually shows.

The most dangerous misconception I encounter is the assumption that modern cannabis is the same plant from the 1970s. That comparison is pharmacologically meaningless.

In the Woodstock era, cannabis seized by law enforcement typically contained 1-3% THC. By 1995, average potency had risen to about 4%. The acceleration continued: 12% by 2014, and today's dispensary flower products routinely test between 18-35% THC. Some premium strains reach 40%.

But the potency story extends far beyond flower. Cannabis concentrates marketed as dabs, wax, shatter, or vaping liquids contain THC concentrations of 60-99%. Meanwhile, the THC-to-CBD ratio has shifted dramatically. Where cannabis once contained a natural balance of THC and CBD (which mitigates some of THC's adverse effects), modern products often have ratios of 80:1 or higher.

When a 75-year-old uses a modern vape cartridge or high-potency edible, they are experiencing a psychoactive load 20 to 50 times stronger than what they may have encountered decades ago. In the aging brain, this is the difference between mild relaxation and acute delirium.

The pharmacology of cannabis in older adults is fundamentally different from younger populations. Several age-related changes converge to amplify risk.

Altered distribution and clearance. THC is highly lipophilic, meaning it dissolves readily in fat. As we age, our ratio of fat to lean muscle increases, even in otherwise healthy seniors. This creates a larger reservoir for THC storage. Combined with reduced liver and kidney function that slows metabolic clearance, the half-life of THC extends significantly in older adults. A single use can produce cognitive fog, impaired balance, or confusion that persists for days.

Cardiovascular vulnerability. THC acutely increases heart rate and blood pressure while simultaneously triggering orthostatic hypotension, the sudden drop in blood pressure upon standing. A 2025 meta-analysis found that cannabis users faced substantially elevated risks of heart attack, stroke, and heart failure. Daily use elevates heart failure risk by 34% compared to never-users. The cardiovascular risk peaks approximately one hour after consumption.

Polypharmacy interactions. The average older adult takes multiple medications, and 83% of adults in their sixties and seventies use five or more. Cannabis and its components are metabolized by the same liver enzymes (cytochrome P450) that process anticoagulants, antidepressants, benzodiazepines, opioids, and statins. Adding cannabis to a complex medication regimen introduces unpredictable drug interactions that can range from therapeutic failure to toxicity.

The "natural" label on cannabis does not grant it immunity from the laws of geriatric pharmacology.

The intersection of cannabis use and mental health in older adults reveals a complex picture. Cross-sectional studies consistently demonstrate that older cannabis users experience depression, anxiety, and substance use disorders at rates two to three times higher than non-users. The relationship appears bidirectional: some older adults self-medicate psychiatric symptoms with cannabis, but increasing use also correlates with worsening mood.

The anxiety paradox. Nearly a quarter of older cannabis users cite anxiety relief as a reason for use. Yet high-THC products can trigger panic attacks, and the evidence does not support cannabis as an effective treatment for anxiety disorders in this population. The effects of THC on anxiety are dose-dependent and often biphasic, with low doses sometimes calming and higher doses frequently anxiogenic.

Cognitive concerns. A 2025 Ontario study examined individuals who required emergency care for cannabis-related reasons. Within five years, 18.6% had developed dementia. Even after adjusting for age and chronic conditions, those with acute cannabis-related healthcare encounters faced a 1.72-fold increased risk of dementia compared to the general population. This finding suggests association, not proven causation, but it should give pause to anyone assuming cannabis is cognitively benign. For more on cognitive assessment and early detection, see my earlier post on The New Alzheimer's Blood Tests.

Psychosis risk. High-potency THC products amplify psychosis risk significantly. Paranoia is the most common acute symptom, and older adults are particularly vulnerable to delirium and confusion due to age-related changes in brain structure and receptor sensitivity.

As clinicians, we need to move beyond binary thinking about cannabis. It is neither the demon drug of Reefer Madness nor the harmless herb of wellness marketing. The evidence demands nuance.

The data on cannabis-impaired driving are sobering. Meta-analyses demonstrate that acute THC intoxication increases motor vehicle collision risk by 36-55%. Impairment from inhaled THC lasts at least 4-5 hours; oral products impair for longer. Critically, self-assessment of driving ability is unreliable during the impairment period. People feel capable of driving long before their actual skills have recovered.

Older adults are particularly vulnerable. A case-control study found that the difference in crash risk between THC-positive and sober drivers becomes statistically significant at age 64. After cannabis legalization in British Columbia, the greatest increase in THC prevalence among injured drivers occurred in those 50 years and older.

One in five older cannabis users report driving within two hours of consumption. Daily users have more than three times the odds of driving after cannabis use compared to occasional users.

The compounding problem. Many older patients present with what appears to be "manageable" polypharmacy and mild cognitive changes. But consider the cascade:

Each adds incremental impairment. Together they create cumulative deficits that may not be apparent in a structured office visit. This is impairment hidden in plain sight.

We screen for drunk driving. We should be equally vigilant about impaired driving in patients already navigating cognitive decline and polypharmacy. For patients with any degree of cognitive impairment, the stakes multiply. This connects directly to the importance of early cognitive screening, which I discussed in The New Alzheimer's Blood Tests.

Given the risks outlined above, patients and families often ask about alternatives they perceive as safer. Three deserve specific attention.

Often marketed as "cleaner" than smoking, vaping actually introduces unique dangers that are particularly hazardous for seniors.

Vaping delivers THC to the bloodstream with remarkable efficiency, bypassing the liver's first-pass metabolism that moderates the effects of edibles. Blood THC levels peak within minutes rather than the 45-90 minutes typical of oral products. This rapid spike makes it nearly impossible to implement "start low, go slow" principles, and the sudden cardiovascular stress is especially dangerous for older adults with heart disease.

The 2019 outbreak of e-cigarette or vaping product use-associated lung injury (EVALI) brought attention to acute pulmonary risks. Among hospitalized EVALI patients, over 80% reported using THC-containing vape products, with most obtained from informal sources rather than licensed dispensaries. While vitamin E acetate was implicated, the full mechanism of injury remains incompletely understood.

The vapor produced by these devices is not just water vapor. It is a complex aerosol containing volatile organic compounds and potentially heavy metals from heating coils. For seniors already managing COPD or cardiac disease, these exposures can tip the balance toward acute respiratory distress.

Vaping is not safer for this population. It may be more dangerous.

Gummies and other edibles seem approachable, but they introduce a different risk profile. Onset is delayed 45-90 minutes, sometimes longer. Older adults frequently redose before the first dose takes effect, leading to unintentional overdose. Once absorbed, effects last 6-8 hours or longer in seniors with slow hepatic clearance.

Absorption is unpredictable and increases with fatty meals. Cannabis poisoning among older adults tripled after edible legalization in Canada. The delayed onset that makes edibles seem gentler is actually what makes them dangerous. Patients cannot titrate in real time.

"Can I just use CBD? It doesn't have the marijuana in it."

The short answer: CBD is not "marijuana-free," not risk-free, and not evidence-based for most conditions seniors use it for. Whether derived from hemp or marijuana, CBD is a cannabinoid extracted from cannabis. The only FDA-approved CBD product is Epidiolex, approved for specific pediatric seizure disorders. For anxiety, pain, insomnia, and inflammation, marketing has outpaced science.

Drug interactions are real. CBD is a potent inhibitor of cytochrome P450 enzymes, particularly CYP2C19, CYP3A4, and CYP2D6. It can increase blood levels of warfarin (raising bleeding risk), clobazam, tacrolimus, SSRIs, and statins. Independent analyses show that over-the-counter CBD products frequently misrepresent their cannabinoid content, with some containing undisclosed THC concentrations sufficient to cause unintended intoxication.

A related concern involves synthetic cannabinoids. FDA-approved synthetics like dronabinol (Marinol) offer standardized dosing for specific indications. But illicit synthetics marketed as "K2" or "Spice" are 50-100 times more potent than natural THC and have caused deaths. Patients should avoid them entirely.

This is not about prohibition or blanket permission. It is about applying the same evidence-based rigor we use for any other medication decision.

The gap between cultural acceptance and clinical evidence is widening. Millions of older adults are navigating this landscape with limited professional guidance, and the marijuana they encounter is fundamentally different from what existed even a decade ago. Meanwhile, only 23% of older adults report that their physician has ever asked about cannabis use.

For patients using cannabis who also struggle with depression, anxiety, or treatment-resistant mood disorders, evidence-based alternatives exist. I have written previously about advances in neuromodulation and interventional psychiatry that offer options beyond self-medication.

The path forward requires collaboration between patients, families, and healthcare providers, rooted in evidence rather than assumption, and guided by the principle that protecting function and independence matters more than following trends.

If you are a clinician, ask the question. If you are a family member, start the conversation with the care team.

I would love to hear from you. What has been your experience with older patients or family members using cannabis? Are you seeing the same trends in your practice or community? Reply to this email or leave a comment below.

For more on the evolving landscape of psychiatric care, explore Psychiatry 3.0, where evidence-based psychiatry meets precision medicine and the art of understanding.

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