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The juxtaposition of 2 recent research reports should give us pause for concern. In September, the National Institute on Drug Abuse reported that 

 use among college students reached 44% in 2020, a significant increase from 38% in 2015 and at its highest level since the 1980s.

 currently available is more potent than that used in the past. This follows a July report from researchers in Denmark who claim that the increasing use of cannabis is a likely cause of increasing incidence of schizophrenia noted in that country over the past 2 decades.

 An increasing incidence of schizophrenia, or psychosis in general, has also been reported in England, Switzerland, and Canada, especially among young people.

 Since 19 US states have already legalized the recreational use of cannabis and other states are considering doing so, a possible relationship between cannabis use and increasing 

 is potentially very important and needs to be confirmed.

The National Institute of Mental Health (NIMH) website describes itself as “the lead federal agency for research on mental disorders.” Schizophrenia is generally considered to be the most disabling mental disorder and in 2013 was estimated to cost the US $155.

 One would therefore expect NIMH to have accurate information on the incidence and prevalence of schizophrenia and some idea whether they are increasing, decreasing, or constant over time. However, when a health reporter asked NIMH for its reaction to the report on cannabis and 

 from Denmark, a NIMH spokesperson had little to offer other than to say that “it’s hard to obtain accurate estimates of the prevalence of schizophrenia because diagnosis is complex and it overlaps with other disorders.”

In fact, NIMH says that it does not know the prevalence of schizophrenia in the US other than within broad limits.

 For the last 4 years, the NIMH website has combined schizophrenia with other “related psychotic disorders” and claimed that together, their prevalence is “between 0.25% and 0.64%” of the population, which translates to between 772,000 and 2.0 million individuals. For every other mental disorder, except schizophrenia, NIMH provides a precise prevalence number.

Part of the problem is that NIMH has not undertaken a serious study of the incidence or prevalence of 

 or other major mental illnesses in 40 years. At that time, it reported the 1-year prevalence of schizophrenia among adults in the US to be 1.1%, equivalent to 2.6 million adults based on 2010 census data.

 NIMH used that percentage as its official estimate for the prevalence of schizophrenia until 2017. At that time, for reasons it has yet to explain, NIMH declared that the true prevalence of adult schizophrenia was really only 0.3%, or 704,000 individuals. As justification for this new number, NIMH cited a study from 2005that only counted people with schizophrenia who were living at home (including college students); those residing elsewhere—including hospitals, group homes, 

 Since NIMH had effectively made 2 million people with schizophrenia disappear without justification, the number was publicly ridiculed.

 NIMH’s response was to acknowledge that it really does not know the prevalence and to offer the range of numbers cited above.

In order to ascertain whether any disease is increasing or decreasing over time, one needs a reliable baseline number as well as repeated surveys. Since NIMH has never repeated the prevalence survey for the 40-year-old study or established another reliable baseline number, it has no way to tell whether schizophrenia is increasing or decreasing. In fact, since the 1990s, there are suggestions that it may be increasing. The number of seriously mentally ill individuals who are homeless or incarcerated has appeared to increase in recent years, and schizophrenia is a significant part of that population. Schizophrenia is a major, and apparently increasing, contributor to the cost of the Medicaid and Medicare programs. And the “mental disorders” diagnostic category has been 1 of the fastest-growing parts of the Supplemental Security Income and Social Security Disability Income programs.

It is an embarrassment to American medicine that NIMH has so little to contribute on such an important question. At a minimum, NIMH should issue a request for proposals to try and confirm the Danish study in another country which has appropriate data so that we will have a definitive answer to this question.

is the founder of the Treatment Advocacy Center and the author of 

American Psychosis: How the Federal Government Destroyed the Mental Illness Treatment System

1. Marijuana use at historic high among college-aged adults in 2020. National Institute on Drug Abuse. September 8, 2021. Accessed December 22, 2021. 

https://www.drugabuse.gov/news-events/news-releases/2021/09/marijuana-use-at-historic-high-among-college-aged-adults-in-2020

2. Hjorthøj C, Posselt CM, Nordentoft M. 

Development over time of the population-attributable risk fraction for cannabis use disorder in schizophrenia in Denmark.

3. Boydell J, Van Os J, Lambri M, et al. 

Incidence of schizophrenia in southeast London between 1965 and 1997.

4. Ajdacic-Gross V, Lauber C, Warnke I, et al. 

Changing incidence of psychotic disorders among the young in Zurich.

Increase in schizophrenia incidence rates: findings in a Canadian cohort born 1975-1985.

6. Cloutier M, Aigbogun MS, Guren A, et al. 

The economic burden of schizophrenia in the United States in 2013.

7. Hunt K. Schizophrenia linked to marijuana use disorder is on the rise, study finds. CNN Health. July 22, 2021. Accessed December 22, 2021. 

https://www.cnn.com/2021/07/22/health/marijuana-schizophrenia-study-wellness/index.html

8. Gordon JA. On the prevalence of schizophrenia-and transforming care through research. 

https://www.psychiatrictimes.com/view/prevalence-schizophrenia-and-transforming-care-through-research

9. Gordon JA. Letter to Senator Bernard Sanders. February 6, 2019.

10. Regier DA, Narrow WE, Rae ES, et al. 

The de-facto US mental and addictive disorder system. Epidemiologic Catchement Area retrospective 1-year prevalence rates of disorders and services.

11. Kessler RC, Birnbum H, Demler O, et al. 

The prevalence and correlates of nonaffective psychosis in the National Co-Morbidity Survey Replication (NCS-R).

12. Torrey EF, Sinclair E. Hocus pocus: how the NIMH made 2 million people with schizophrenia disappear. 

https://www.psychiatrictimes.com/view/hocus-pocus-how-nimh-made-2-million-people-schizophrenia-disappear

13. Torrey EF, Simmons W. Where did the schizophrenics go? 

. March 26, 2019. Accessed December 22, 2021. 

https://www.wsj.com/articles/where-did-the-schizophrenics-go-11553640973

14. Torrey EF. Severe psychiatric disorders appear to be increasing. 

https://www.psychiatrictimes.com/view/severe-psychiatric-disorders-may-be-increasing

Is cannabis’ effect on schizophrenia being downplayed? 

Is Cannabis Use Increasing Schizophrenia? 

, about her innovate approach to drug use among teenagers. Avoiding old-fashioned scare tactics, Martinez talks to students and their parents about the neurological effects of substances like cannabis and alcohol. Could scientific education be a key protective factor against addiction?

The rising rate of teen cannabis use and its potential causes.

The effects of smoking marijuana on brain development.

How other psychiatric illnesses can lead to substance abuse disorders.

How to talk to teenagers about substance use—without being overbearing.

Distinguishing between experimental and problematic substance use.

is a child and adolescent psychiatry fellow at New York-Presbyterian Hospital.

Thanks to Columbia University Department of Psychiatry for allowing us to present the Caring for Teens and Tweens podcast with experts in the field of psychiatry.

Scare tactics don’t work. But scientific education might. Here are tips for talking with teenaged patients about keeping themselves and their friends safe. 

How to Talk to Teenagers About Substance Use

Prior to my decision to attend medical school, I was planning to become a basic science researcher. I studied biochemistry in college at a time when it was a relatively young field. My bachelor of science curriculum included 7 semesters of chemistry; 5 semesters of biochemistry, physics, microbiology, and zoology; and a senior honors thesis that entailed designing, completing, and defending a novel research project. I successfully defended my thesis, “An Analysis of the Fate of the Escherichia coli 4.5S RNA Gene in Yeast Using a Recombinant Plasmid,”

 and was planning to attend graduate school in genetics at the University of Washington in Seattle.

Between completing my senior thesis and my planned move to Seattle, I suddenly panicked and wondered: Is this truly the career path for me? Ultimately, I realized I did not have what it took to be a basic science researcher, so I worked for a year as a biochemical technician and applied to medical school—a decision I have never regretted.

Yet, I do not regret my background in biochemistry either. It is the foundation upon which all I have learned of medicine and psychiatry is built. The field of neuropsychopharmacology has evolved over the past 30 years, and I am filled with pride, awe, and excitement to have witnessed the clinical advancements that basic science researchers have made possible. However, in my opinion, there is 1 significant exception to all my accolades for how good science has advanced medicine: the research on cannabis.

The scientific method is used in medicine and has been the established paradigm for scientific inquiry since the 1600s. Thus, all clinical trials submitted to the US Food and Drug Administration (FDA) are meticulously designed to answer a primary outcome question about the drug under investigation. A necessary requirement of the study design is to ensure that the variables in the various arms of the study are identical except for one: drug A at dose X compared with placebo. If multiple doses of drug A or multiple drugs are being compared, each arm is precisely characterized so the conclusions drawn from the primary outcome will be highly accurate and reliable.

Over the past 10 years, I have read numerous articles in the psychiatric literature that draw conflicting conclusions about the effect of cannabis on cognition, its attendant risk of psychosis, its addictive potential, and its effect on suicidality, and about its impacts on depression, anxiety, pain relief, and apathy. (There appears to be only 1 consistent finding: Heavy cannabis use during brain development increases the risk of psychosis and cognitive impairment, especially when other risk factors are present.) A likely explanation for the wide-ranging discrepancies is that cannabis is the product of a plant that is not a single molecule or pure substance. Many articles with the word cannabis in the title can be discarded as meaningless unless the authors took the additional step of testing all of the cannabis used by their study subjects for the quantitative and qualitative molecules present.

It is well established that cannabis contains 

 These constituents include more than 100 cannabinoids, more than 200 terpenoids (terpenes), and numerous flavonoids. Two cannabinoids are most prevalent in cannabis: Δ-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), both of which exist in an extremely wide range of ratios depending on the specific strain of cannabis assayed. Significantly, these 2 cannabinoids are oppositional in their clinical effects and have dramatically different pharmacodynamic effects. In reviewing the literature on cannabis, a consistent finding is that potency of cannabis is a proxy for the amount of THC. Although this is likely a result of the psychoactive effects of cannabis that have been noted for more than 6000 years,

 CBD has surfaced as an important cannabinoid with many positive medicinal properties. Notably, cannabis remains a Schedule 1 drug by the Drug Enforcement Administration (DEA), while CBD is unscheduled.

documents some of the significant differences between THC and CBD. Despite these differences, the vast majority of publications on cannabis draw conclusions based on participants’ self-reports of quantity and frequency of cannabis use. In these studies, the molecular components of the cannabis used are not known, nor is the important ratio of THC to CBD.

A fair analogy would be to evaluate a new drug; let us call it Sedalant. Sedalant contains a wide-ranging ratio of 2 molecules with different mechanisms of action: one a sedative, and one a stimulant. Without knowing the exact ratios and concentrations of each of these molecules in clinical studies of Sedalant, no evidence-based conclusions could be drawn from the drug studies.

Naturally occurring cannabis plants produce roughly an equal ratio of THC to CBD, containing approximately 2% of each. However, over the decades, with selective breeding in some strains, THC has been increased significantly while CBD has been virtually bred out. 

 analyzed the concentrations of THC and CBD from 38,681 samples of illegal cannabis seized by the DEA between 1995 and 2014. The authors found a clear trend of increased THC in cannabis over time, with an average concentration of 4% in 1995 that increased to 12% in 2014. Simultaneously, CBD concentration steadily declined, from 0.5% in 2004 to less than 0.2% in 2014. The investigators concluded that the ratio of THC to CBD increased from 14-fold in 1995 to 80-fold in 2014.5 Some strains of cannabis today may contain up to 30% THC with virtually no CBD, while other strains have high concentrations of CBD with minimal THC.

To further complicate the cannabis story, very few of the other cannabinoids in cannabis plants have been characterized pharmacodynamically or pharmacokinetically. The characterization of 3 of these more than 100 cannabinoids—Δ-9-tetrahydrocannabivarin, cannabichromene, and cannabigerol—tells us that they are 

Interestingly, the odors (skunk is a common description) often associated with cannabis are largely due to the complex combination of terpenes, another compound that complicates the study of cannabis. (Cannabinoids are odorless.) An extensive literature documents the essential role terpenes play in the biology of the cannabis plant, the plant’s production of cannabinoids, and the properties of a specific strain of cannabis that help determine its market value. Terpenes likely also contribute pharmacodynamic and pharmacokinetic effects that impact the neuropsychopharmacology resulting from ingestion of each different strain of 

Several publications since 2018 have appropriately concluded that we know very little about the range of pharmacological effects from cannabis due to the large variability of cannabinoids, terpenes, and flavonoids that are present in 

For this very reason, it would be contrary to the scientific method of research to attempt to gain FDA approval of cannabis.

Only 1 of the more than 100 cannabinoid components in cannabis has been sufficiently studied to receive FDA approval: CBD. Following a comprehensive analysis as well as clinical trials of pure CBD, it received 

 for the treatment of seizures in Dravet syndrome and in Lennox-Gastaut syndrome in children and adults.

 We may see additional approvals in the future for this well-studied compound, as a growing and consistent body of evidence shows that pure CBD in defined dosages has antipsychotic effects in patients with schizophrenia.

The practice of medicine is built upon evidence-based treatments that have been appropriately vetted by well-established protocols. CBD traveled this path to become an FDA approved drug, and so should any other component of the 500-plus molecules in cannabis. Accordingly, clinical publications should be held to a higher standard of identifying and defining what components of cannabis are relevant in any article being submitted for publication.

With each passing year, more US states legalize cannabis for medical use, recreational use, or both. It is likely that federal laws will eventually make cannabis use legal on a national level. That will create an opportunity to require a comprehensive analysis and disclosure of all the components of the numerous strains of cannabis currently being sold in state dispensaries or on the streets. Concurrently, the individual molecular components of the cannabis plant should be identified and pharmacologically characterized. This would create a treasure trove of possible drug candidates for specific clinical indications, and it would allow for a more informed choice when choosing a cannabis product.

In this scenario, cannabis should be regulated federally similar to tobacco products and alcohol. Both of these have significant risks, and both are tightly controlled. Ideally, the taxes imposed on federally regulated cannabis could help fund the extensive research needed to allow a more competent understanding of the complex combination of molecules that different strains of cannabis contain.

1. The word cannabis should not be used casually in medical literature, as it is nonspecific and includes varying molecular combinations of diverse cannabinoids, terpenes, and flavonoids.

2. Future research involving cannabis should use a single strain in each study; each strain used should be analyzed quantitatively and qualitatively for biologically active components.

3. If multiple strains are used in a clinical trial, they should be analyzed (as noted in #2), and each strain should be studied as a separate arm compared with placebo.

4. Increased funding is needed to accurately characterize the 500-plus molecular components of the cannabis plant, including the pharmacokinetics and pharmacodynamics of each component.

5. A public education campaign should aggressively disseminate the molecular facts about cannabis, especially the oppositional effects of THC and CBD. Similarly, the risks of increased psychosis and cognitive impairment with heavy regular use of THC in the developing brain should be explained, much like disclaimers on alcohol about drinking during pregnancy.

6. Cannabis should be federally legalized and regulated similarly to alcohol and tobacco products.

7. Cannabis should not be regulated by the FDA due to its extreme heterogeneity of components and the associated unpredictable pharmacological properties.

8. Cannabis should not be prescribed by medical practitioners. However, as molecular components of cannabis are developed and garnish FDA approval, those components should be prescribed appropriately.

9. Pharmacological exploration and development of cannabis components that demonstrate medical benefits should be continued. CBD is a successful model of such.

10. Medical practitioners should discuss cannabis with their patients only after they have attained competence in understanding the science and factual risks/benefits/adverse effects of cannabis, similar to how a practitioner would discuss alcohol or tobacco use.

With this structure in place, we have the ability to inform and support our patients appropriately. And, with more information, we can help end the cannabis confusion.

 is medical director, Brain Health, Exeter, New Hampshire; Editor in Chief,

; staff psychiatrist, Seacoast Mental Health Center, Exeter; Consulting Psychiatrist, Exeter Hospital, Exeter; Consulting Psychiatrist, Insight Meditation Society, Barre, Massachusetts.

1. Miller J. An Analysis of the Fate of the Escherichia coli 4.5S RNA Gene in Yeast Using a Recombinant Plasmid. Senior undergraduate honors thesis. University of Washington, Amherst; 1981.

2. Lafaye G, Karila L, Blecha L, Benyamina A. Cannabis, cannabinoids, and health. 

4. Atakan Z. Cannabis, a complex plant: different compounds and different effects on individuals. 

5. ElSohly MA, Mehmedic Z, Foster S, et al. Changes in cannabis potency over the last 2 decades (1995-2014): analysis of current data in the United States. 

6. ElSohly MA, Radwan MM, Gul W, et al. Phytochemistry of Cannabis sativa L. 

7. Nachnani R, Raup-Konsavage WM, Vrana KE. The pharmacological case for cannabigerol. 

8. Sommano SR, Chittasupho C, Ruksiriwanich W, Jantrawut P. The cannabis terpenes. 

9. Booth JK, Bohlmann J. Terpenes in cannabis sativa – from plant genome to humans. 

10. Baron EP. Medicinal properties of cannabinoids, terpenes, and glavonoids in cannabis, and benefits in migraine, headache, and pain: an update on current evidence and cannabis science. 

11. Jett J, Stone E, Warren G, Cummings KM. Cannabis use, lung cancer, and related issues. 

12. Epidiolex. Greenwich Biosciences; 2020. Updated April 2020. Accessed July 7, 2021. 

13. McGuire P, Robson P, Cubala WJ, et al. Cannabidiol (CBD) as an adjunctive therapy in schizophrenia: a multicenter randomized controlled trial. 

14. Elsaid S, Le Foll B. The complexity of pharmacology of cannabidiol (CBD) and its implications in the treatment of brain disorders. 

15. National Academies on Sciences, Engineering, and Medicine. 

The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research

16. Rong C, Carmona NE, Lee YL, et al. Drug-drug interactions as a result of co-administering Δ9-THC and CBD with other psychotropic agents. 

10 keys to understanding the science of cannabinoids. 

Cannabis Confusion

Patients increasingly ask about cannabis and whether it can be useful for sleep, PTSD, pain, and even dementia. In this video, Timothy W. Fong, MD gives a brief overview on emerging issues in cannabis. On Monday, May 3, Dr Fong and colleagues will speak at this year’s APA meeting in a presentation titled “

Facing the Challenge of Cannabis Legalization: Psychiatry’s Role

Dr Fong is Professor of Psychiatry & Director, UCLA, and Co-Director of UCLA’s Gambling Studies. The presentation is in collaboration with Laurence Westreich, MD; Kevin Allen Sevarino, MD; and Frances Rudnick Levin, MD.

Timothy W. Fong, MD, touches on our current understanding about cannabis use for psychiatric disorders.

Addressing Myths and Facts About Cannabis Use

For the full report of survey results, see 

You Spoke, We Listened. Psychiatry's Cannabis Survey

Clinical Management of Cannabis Complications


Thomas R. Kosten, MD, and Christopher D. Verrico, PhD

The Age of Cannabis Has Arrived: Issues for Older Adults

Cannabis 2021: What Clinicians Need to Know

Cannabis and Psychosis: A Synthesis of Quantitative Reviews

How to Discuss Cannabis With Your Patients

Infographic: A Snapshot of Psychiatrists' Attitudes Toward Cannabis

Research on psychiatrists' attitudes on the potential of cannabis in psychiatry.

Infographic: A Snapshot of  Psychiatrists' Attitudes Toward Cannabis

Enlightening survey results reveal what psychiatrists think about medical marijuana/cannabis use, how or whether to discuss with their patients, and what biases might get in the way of such conversations.

A new question must be added to the list that mental health clinicians ask their older patients while taking a history, regardless of age: “Have you used any cannabis products recently?”

I learned this lesson during a follow-up appointment with an 82-year-old man with Alzheimer disease. He reported some rather abrupt cognitive decline, and I asked him and his wife about recent medical changes without finding any clear precipitant. Finally, his wife sheepishly confessed that their son had sent them a grab bag of cannabis-derived products that the patient was taking. The family was desperate for anything to help his cognitive decline and they had heard that cannabis was a miracle cure for Alzheimer disease and many other conditions. Unfortunately, the patient received no benefit but did experience some mild, noticeable adverse effects. Without my probing, I never would have known. The next patient I asked explicitly about using cannabis products responded in an equally explicit manner: “No I haven’t,” he said, “but can you get me some?” It was clear that the age of cannabis had arrived.

Older individuals with psychiatric disorders are increasingly using cannabis, largely in the form of prescribed medical marijuana and cannabidiol (CBD). This trend has been driven by several factors: reduced stigma, lifted restrictions on possession and sale by most states, and the enormous proliferation of articles and ads that tout supposed benefits of 

 for many conditions that afflict the elderly, including chronic pain, peripheral neuropathy, stress, anxiety, depression, insomnia, headaches, and the adverse effects of chemotherapy.

 As a result, medical marijuana use by individuals 65 or older has increased more than 8-fold in recent years, from less than 0.5% in 2006 to 4.2% in 2018

). In a survey of 345 adults in Colorado, 16% had used medical marijuana since legalization, with half the users being 75 or older.

 CBD has seen a particularly enormous surge in interest and availability after it was exempted from federal regulations in the 2018 US Farm Bill. Since then, it is estimated that 6.4% of adults aged 45 to 55 and 3.7% of those 55 or older have used CBD at least once.

Although the cannabis sativa plant contains hundreds of chemicals known as cannabinoids, the 2 main active chemicals are Δ-٩-tetrahydrocannabinol (THC) and CBD. THC has both psychotropic and euphoric properties and confers the high associated with marijuana, while CBD is noneuphoric because it does not activate the cannabinoid 1 receptor like THC does. The same plants that produce THC also produce CBD. Both THC and CBD come in a variety of forms; they can be smoked, vaped, eaten, ingested as liquids, used as oils, and applied via creams and cosmetics.

The psychotropic effects of both THC and CBD are mainly because of their interaction with endogenous cannabinoid receptors in the brain, as well as activation of a variety of other cannabinoid and noncannabinoid receptors (ie, serotonergic, glutaminergic, µ-opioid, and α1-adrenergic) in the central nervous system and on immunologic cells. Based on their known and theorized properties, marijuana and CBD have been proposed as remedies to modulate symptoms of stress, insomnia, pain, inflammation, and cognitive impairment, particularly in older individuals. As a result, there are many unsubstantiated claims that THC and/or CBD can treat Alzheimer disease, Parkinson disease, schizophrenia, and anxiety and mood disorders.

Several small case series have suggested a tentative basis for some of these claims. For example, a study looked at the use of an oral spray containing THC and CBD for peripheral nerve pain and found that it was well tolerated and showed a trend toward improvement in pain and sleep.

 Medical marijuana use has been associated with some improvement in both movements and neuropsychiatric symptoms in individuals with Parkinson disease.

 One small case series found improvement in behavioral and psychological symptoms of dementia from cannabis oil containing THC.

 A related randomized control trial of 50 individuals with dementia and associated neuropsychiatric symptoms did not see any benefit from THC, but did find it was well tolerated and with no appreciable effect on memory.

 Despite these limited data, agitation associated with dementia is a qualifying condition for medical marijuana in several states.

Gruber and colleagues studied a sample of middle-aged individuals using medical marijuana over 3 months and found improvements in 

 and reductions in depression, insomnia, and impulsivity.

 They also saw a reduction in the use of benzodiazepines and opioids as well as a normalization of brain activation waves to states seen in normal controls. It is not clear, however, if these neurocognitive results were the direct result of the medical marijuana or an indirect benefit of decreases in pain, anxiety, and 

Although there are many other in vivo, in vitro, and animal studies of THC and CBD, it is clear that evidence is limited, and there are few randomized controlled trials to support most of their theorized clinical benefits. In addition, these studies are based on a variety of cannabis products from multiple sources and with variable contents.

 The 2 exceptions include a Food and Drug Administration (FDA)-approved form of synthetic THC known as dronabinol, which is used for treating appetite and weight loss resulting from AIDS as well as nausea and vomiting from chemotherapy, and a medication containing CBD for the treatment of 2 rare childhood seizure disorders. Dronabinol has also been studied in Alzheimer disease to treat anorexia and agitation and was found to be well tolerated with variable efficacy for both conditions.

, a CBD-THC combination, has been approved for the treatment of muscle spasms associated with multiple sclerosis.

The use of medical marijuana and CBD in older adults must be approached with caution because there are several potential adverse effects. It has been well established that heavy marijuana use in both young and middle-aged adults can cause mild functional and structural brain impairments affecting attention, 

, motor coordination, verbal memory, and executive function.

 Although these effects may be more variable with lighter use in older adults, they may be amplified by preexisting brain impairment as well as by underlying pulmonary and cardiovascular conditions, especially when medical marijuana is smoked or vaped.

 One review of 184 older patients (median age, 82) who were on medical marijuana for 6 months found that approximately 80% reported some benefit for the treated symptoms, but one-third reported adverse effects, including dizziness (12%) and sleepiness and fatigue (11.2%).

 Other reported adverse effects from a national epidemiologic survey included changes in mood and cognition, psychosis, increased heart rate and blood pressure, urinary retention, and blurred vision.

 In addition, THC has been associated with impaired driving in young adults, which could also be a problem in older drivers who may be impaired at baseline.

 of CBD use found that it is generally well tolerated with few adverse effects, the most common one being diarrhea.

 Other adverse effects associated with CBD include nausea, drowsiness, fatigue, dry mouth, and mood changes. Keep in mind that CBD is an inhibitor of several cytochrome P450 enzymes, including CYP1A2, CYP2B6, CYP2C9, CYP2D6, and CYP3A4. CBD can lead to drug-drug interactions with several commonly used medication groups in older patients, including blood thinners, antibiotics, anticonvulsants, antidepressants, and antipsychotics.

What To Ask Patients, and What To Tell Them

In this new era of medical marijuana and CBD, there are several important takeaways for clinicians working with older patients. Do not assume that because a patient is elderly and has physical or cognitive limitations that they do not fit the profile of a cannabis user. To the contrary: Every older patient along with their caregivers should be queried as to their use of cannabis, whether recreationally, from mail order or friends and family, or through a prescription. To this end, every clinical history should include questions about the use of cannabis products, including the stated reasons for use, the type of marijuana or CBD being used, and observed benefits and adverse effects. Concomitant medical conditions must be reviewed for potential vulnerabilities, such as an individual with hypertension using a product that increases blood pressure or heart rate, or an individual with chronic obstructive pulmonary disease using vaping oils. Potential 

 also need to be considered, with a focus on the categories of medications discussed in the article.

Patients and their caregivers need to understand that nearly all benefit claims are largely unsubstantiated, as they lack a rigorous scientific basis. Slick articles and ads generally exaggerate potential benefits, or they refer to in vitro or animal studies and anecdotal reports, making them sound as if they constitute direct evidence of clinical effects. They also need to understand the differences between THC and CBD, along with the fact that production is largely unregulated, so products can have many different ingredients and properties. Several studies have found wide discrepancies between labels for cannabis products and their actual contents, especially when it comes to the amount of THC or CBD.

 Thus, many products that claim only to have CBD actually have varying degrees of THC present. This lack of consistency often accounts for both inconsistent clinical effects as well as adverse effect issues, and these factors lead many older adults to discontinue use of cannabis products.

Finally, keep in mind that older patients with preexisting 

 such as in Alzheimer disease might be particularly vulnerable to adverse effects such as drowsiness, dizziness, fatigue, and mood changes, which in turn can account for significant and unpredictable fluctuations in cognition and behavior. Such unpredictability (in the amount of drug being ingested over time and the ensuing effects on brain and body) is exactly the sort of variability that can be hazardous in the older patient. Compounding these risks is the fact that many individuals will use products such as CBD oil without the knowledge and supervision of a knowledgeable clinician.

The bottom line is that more rigorous scientific study using randomized controlled trials is needed to substantiate the proposed benefits of cannabis and more fully understand the range and impact of common adverse effects.

is the chief medical officer at MIND Institute at Miami Jewish Health.

1. Gruber SA, Sagar KA, Dahlgren MK, et al. 

Splendor in the grass? A pilot study assessing the impact of medical marijuana on executive function

2. Grinspoon P. Older adults and medical marijuana: reduced stigma and increased use. 

Updated April 6, 2020. Accessed February 1, 2020. 

https://www.health.harvard.edu/blog/older-adults-and-medical-marijuana-reduced-stigma-and-increased-use-2-2020040119321

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4. Reynolds IR, Fixen DR, Parnes BL, et al. Characteristics and patterns of marijuana use in community-dwelling older adults.

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8. Shelef A, Barak Y, Berger U, et al. Safety and efficacy of medical cannabis oil for behavioral and psychological symptoms of dementia: an-open label, add-on, pilot study. 

9. van den Elsen GA, Ahmed AI, Verkes RJ, et al. Tetrahydrocannabinol for neuropsychiatric symptoms in dementia: a randomized controlled trial. 

10. Maust DT, Bonar EE, Ilgen MA, et al. Agitation in Alzheimer disease as a qualifying condition for medical marijuana in the United States. 

11. Gruber SA, Sagar KA, Dahlgren MK, et al. The grass might be greener: medical marijuana patients exhibit altered brain activity and improved executive function after 3 months of treatment. 

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16. DeFilippis EM, Bajaj NS, Singh A, et al. Marijuana use in patients with cardiovascular disease: JACC review topic of the week. 

17. Abuhasira R, Ron A, Sikorin I, Novack V. Medical cannabis for older patients-treatment protocol and initial results. 

18. Benitez A, Lauzon S, Nietert PJ, et al. Self-reported cognition and marijuana use in older adults: Results from the national epidemiologic survey on alcohol and related conditions-III. 

19. Arkell TR, Vinckenbosch F, Kevin RC, et al. Effect of cannabidiol and Δ9-tetrahydrocannabinol on driving performance: a randomized clinical trial. 

20. Chesney E, Oliver D, Green A, et al. 

Adverse effects of cannabidiol: a systematic review and meta-analysis of randomized clinical trials

Cannabis use has prompted symptoms such as dizziness, sleepiness, and fatigue in older patients. Are there any benevolent effects?

Lost in the various public policy arguments fueling cannabis decriminalization and legalization 

 across the United States is the fact that a percentage of individuals who use cannabis will experience negative effects, ranging from bothersome to the catastrophic. These difficulties arise from a sharply decreasing perception of risk, easy availability of the drug, and increased potency of Δ-9-tetrahydrocannabinol (THC) preparations. The arithmetic of cannabis remains immutable: Best 

 are that about 9% of individuals who use cannabis will become dependent on the substance at some point in their life,

The sharply decreasing perception of risk and easy accessibility of cannabis has many patients turning towards it, despite the potential negative effects. 

Cannabis