For the past two decades, American state governments have operated policy-making laboratories that have created a variety of approaches to legalizing cannabis [1, 2]. Meanwhile, the population continues to grow older, and the total number of Americans who are over 65 years old will soon outnumber children under the age of 18 for the first time in history [3]. Within this dynamic national context, several researchers have observed how cannabis use among older adults has outpaced all other age groups [4, 5]. Initially, the remarkable growth was attributed to the entry of the more “cannabis-tolerant” baby boom cohort into old age, but more recent work has suggested the reasons behind increasing cannabis use are more complex [6–8]. Older persons have responded to changing legal environments, and some are now more comfortable with taking cannabis recreationally. Persons over 65 also are experiencing age-related health-care needs and may use cannabis for symptom management and other “medical” or “therapeutic” purposes. We know little else about the expanding intersection between cannabis and older persons.
In this chapter, we account recent trends in cannabis use among persons over 50 and, when possible, consider trends specific to those over 65. We then review research studies illuminating how older adults have taken different pathways to using cannabis – with some being lifelong users and others who only recently started using cannabis for the first time ever [9, 10]. We also observe outcomes experienced by older persons who use cannabis, making a special effort to present a range of health-related outcomes rather than other outcomes such as school performance. At last, we turn to the critical role physicians and other health-care providers assume in evaluating and advising older persons about cannabis, particularly relative to the use of opioids and other pain management medications.
At this point, it is worth declaring how there is a lack of empirically based knowledge about cannabis and older persons. The research presented in this chapter including the studies reviewed as part of the National Academies of Sciences, Engineering, and Medicine report [11] or based on national surveys such as the National Survey on Drug Use and Health [4, 5, 12–15] falls short in several key ways. For example, most of the research we present does not account for the varieties of cannabis exposure and reveals little about dose, potencies, or routes of administration (e.g., smoking, vaping, edibles), nor do these studies capture substantial differences between marijuana used in clinical trials and commercially available products which are more likely to have increased Δ9-THC (tetrahydrocannabinol) concentrations [16, 17]. We also recognize that most basic and clinical cannabis research rarely includes older adults and those studies which do mostly rely on small samples recruited from limited geographic areas (i.e., states where cannabis is legal). However, rather than concluding this chapter with a standard discussion about the need for more basic and clinical research focusing on cannabis use among older adults, we consider the role of state government policy in further illuminating the intersection between cannabis and older persons.
Cannabis Use Among Older Persons
Cannabis use among older persons has been increasing at a faster rate compared to all other age groups. Data from the National Survey of Drug Use and Health (NSDUH) showed the rate of past-year cannabis use among persons 50 years and older increased by 71.4% between 2006 and 2017. In 2000, the percentage of older persons who had tried cannabis at least once in their lifetime reached 23% among 50–64-year-olds and 3% among those aged 65 and older. By 2011, lifetime usage rates increased to 44% among those between 50 and 64 years old and 17% for persons older than 65 years. The proportion of all persons between 50 and 64 who used in the past year climbed from 2.9% in 2002 to 10.2% in 2016, and among persons over 65, there was more than a tenfold increase as past-year rates grew from 0.2% to 3.7% [4, 5].
While the overwhelming majority of the estimated four million Americans older than 50 years who currently use cannabis are healthy, well-educated, and white, researchers have observed several significant individual differences among these users [13–15]. The NSDUH data indicated that older persons who used cannabis in the past year (i.e., current users) were statistically more likely to have started taking cannabis before the age of 30, with many starting before the age of 18 although researchers also have observed a growing number of older users re-engaging after stopping in midlife or who are naïve, first-time users [18]. Others [19] reported past-year marijuana users identified smoking/inhaling as their preferred method, but a large and growing number of older adults also use edibles and topical formulations (i.e., creams and ointments).
Nearly half of older persons who used consistently in the past year are lifetime users, and nearly a quarter of these consistent users took cannabis at least three times per week. The majority of all persons older than 50 years who took cannabis in the past year used less than once every 10 days, and 25% of these persons used less than five times during the past year [10, 15]. Past-year cannabis use also has been associated with gender (men are more likely to use than women), marital status (those who are not married are more likely to use), and race (nonwhites are more likely to use than whites). Persons older than 50 years who take cannabis are more likely to smoke cigarettes, drink alcohol, and use cocaine and other illicit drugs including opioids [13, 14, 20].
Cannabis use also is more likely to occur among older persons who experience chronic health conditions and look for cannabis for “medical” or “therapeutic” purposes [18, 19, 21]. Since the NSDUH did not collect data on such an exhaustive range of medical conditions, we looked to clinical observations of smaller patient samples to learn more about the conditions associated with cannabis use. For example, these clinical studies have reported cannabis use by older adults to treat glaucoma-related ocular pressure as well as chronic pain, spasticity associated with multiple sclerosis as well as anxiety and depression [19, 21].
Cannabis use among older adults will continue to increase as more of America’s baby boomers, whose attitudes toward cannabis and other psychoactive drugs historically have been more favorable than their predecessors, reach and surpass their 65th birthdays [8]. Another perspective suggests the decision to take cannabis is based on subjective calculations concerning reward and risk [6], and older individuals living in states with legal marijuana may perceive less risk and may be more likely to use cannabis. As of June 2019, 34 states and the District of Columbia (DC) had approved comprehensive medical marijuana laws (MMLs), and 13 states and DC had laws legalizing recreational cannabis for adult use [2]. In Canada, older persons were the only age-based group to increase use after cannabis was legalized nationally in 2018 [22].
Outcomes of Cannabis Use
Older adults who use cannabis experience a range of outcomes, some beneficial and others harmful. In an effort to organize the variety of outcomes experienced by older cannabis users, we found the Proximal/Distal Model of Health Outcomes to be helpful [23]. This model places health outcomes into four categories: (1) clinical measures, (2) general well-being reports, (3) general functioning reports, and (4) functioning reports specific to disease state or treatment intervention. Regardless of the category they belong to, outcomes fall along a continuum from positive to negative in directionality and in terms of proximity to the individual. For example, a positive proximal outcome for medical cannabis use includes reduction of pain symptoms or sleep issues, and a negative proximal outcome includes increased cognitive impairments. Distal outcomes include the broader areas of mobility, role performance, and life satisfaction, and positive distal outcomes include self-reported improvements in wellness, social engagement, and quality of life, and negative distal outcomes include reduced productivity and adverse event such as emergency room use.
In January 2017, the National Academies of Sciences, Engineering, and Medicine reviewed the health effects of cannabis and its potential for therapeutic use in humans [11]. Most notable, the Academies report found conclusive evidence that cannabis or cannabinoids are effective as an antiemetic in the treatment of nausea and vomiting resulting from chemotherapy. There is substantial evidence that cannabis is effective for the treatment of chronic pain in adult patients and effective for improving patient-reported MS spasticity symptoms. Moderate evidence was found that cannabis is effective for improving short-term outcomes for condition-related sleep disturbances, in addition to improving symptoms of anxiety and PTSD. Other clinical studies completed since then have found cannabis to be effective for relieving pain related to chronic conditions. While few of these studies directly observed persons over 65, one recent survey [24] of 2736 patients above age 65 who were taking cannabis primarily for cancer and chronic pain found participants reported reduced pain and increased quality of life.
Alternatively, the Academies report [11] identified substantial evidence of worsened respiratory symptoms and more frequent chronic bronchitis episodes from long-term marijuana smoking and limited evidence that cannabis use increases the risk of COPD, acute myocardial infarction, ischemic stroke, and prediabetes, particularly for those who intake cannabis through smoking or some other form of combustion. The Academies report also provided substantial and moderate amounts of evidence concerning marijuana’s adverse effects on mental and cognitive health, via the development of schizophrenia or other psychoses, especially due to frequent use during adolescence; impairments in the cognitive domains of learning, memory, and attention from acute use; increased symptoms of mania/hypomania among regular marijuana users with bipolar disorder; increased incidences of social anxiety disorder among regular users; and a slightly elevated risk of depressive disorders and suicide ideation, attempts, and completion among heavier users. Though much of this research rarely included older adults, these adverse effects may be applicable to long-term cannabis users as they grow older.
Other researchers who have deliberately observed older cannabis users have found several problematic outcomes. For example, compared to non-cannabis users, older users have increased psychiatric conditions including anxiety, post-traumatic stress disorder, and bipolar disorder with manic or hypomanic episodes. Cannabis use also has been associated with having more life stressors (interpersonal, financial, legal problems, and being a crime victim), though it remains unclear if cannabis is a cause or correlate to these conditions and episodes [13, 14]. Older adults also were significantly more likely than their non-using age peers to experience an injury, having problems related to driving, and increased use of the emergency department [25, 26]. While the exact mechanisms of injury related to marijuana use are not known, researchers have suggested that cannabis-induced mental status alterations, acute intoxication, and other psychophysiological effects, especially when combined with alcohol and other illicit drugs, may increase users’ vulnerability to injury [27]. According to the Substance Abuse and Mental Health Services Administration, Center for Behavioral Health Statistics and Quality’s Treatment Episode Data [28] on admissions to treatment centers, the proportion of admissions for any substance use problem/disorder among those 50 and over increased from 11.0% in 2006 to 17.9% in 2017. While marijuana was identified as the primary substance in just 3.0% of all older-adult admissions, researchers determined that cannabis use was common among the majority of older adults who are seeking treatment for alcohol, tobacco, and other drug problems.
There certainly is reason to be concerned that increasing cannabis use among older persons may contribute to increasing rates of substance misuse or other undesirable outcomes. However, it is important to note how the overwhelming majority of older cannabis users do not experience any negative outcomes. More than 9 out of 10 of all older persons who took cannabis in the past year reported having no emotional or functional problems, and the majority indicated they placed no self-limit on their use [7].
The Doctor Patient Relationship
As cannabis legalization continues to spread across the United States and the aging population continues to grow, health-care and other service providers increasingly will come into contact with older patients who are (a) continuing their lifetime use of cannabis; (b) restarting cannabis use after not using since early adulthood; or (c) initiating cannabis use for the first time (so-called naive users). As products become more appealing (e.g., edibles and oils), older patients increasingly will seek guidance from a trusted source to learn about using cannabis. Based on focus groups conducted with 137 older adults in Colorado, researchers identified a strong preference among older persons to discuss cannabis with their health-care providers with whom they have ongoing relationships and share their medical histories. The older adults added they would consider personal physicians to be the most appropriate to provide a referral to the state medical cannabis program [21].
As such, medical doctors and other health professionals should become familiar with the varied pathways of cannabis use among older adults and the corresponding range of outcomes to which these pathways lead. Routine patient evaluations should incorporate questions about cannabis use, like other medications (prescribed and over the counter) and other substances (herbs, supplements, and legal and illegal recreational drugs). Alternatively, if providers do not collect such essential decision-making information, patients using cannabis may experience negative outcomes such as drug interactions and medical complications that could otherwise have been prevented.
In addition, providers should be aware that older adults may be misusing or abusing cannabis, as rates of cannabis use disorder (CUD), as defined in the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (American Psychiatric Association, 2017), among users over 50 years old are slightly less than 5.0%, and several reports have shown cannabis use often co-occurs with other substance use disorders (https://www.drugabuse.gov/publications/).
In fact, older adults who used pain relievers nonmedically were more than three times as likely to be cannabis users, in comparison with those who did not use pain relievers [28].
Opioids, Cannabis, and Pain
Pain is one of the most common health-related conditions experienced by Americans over the age of 65, and the most common approach to addressing pain in older adults is to prescribe medications approved by the US Food and Drug Administration [29–31]. Acetaminophen and nonsteroidal anti-inflammatory drugs are often used to treat mild to moderate levels of pain, whereas older adults with more moderate to severe levels of pain are more likely to be prescribed stronger pain relief in the form of opioids [31]. One study reported that between 1999 and 2010, opioid prescriptions for older-adult outpatients increased from 4% to 9% [32]. In a nationwide study of over 250,000 individuals, the use of prescription opioids was highest among white, educated females between the ages of 70 and 75 [33], and women over age 65 also have higher rates of long-term use of prescription opioids than all other groups over 18 [34]. However, the use of anti-inflammatories and opioids can be problematic. Anti-inflammatory medications have been associated with cardiovascular, gastrointestinal, and renal problems [31, 34]. Opioid use by older adults can result in problematic side effects such as nausea, constipation, sedation, and confusion [34].
Alternatively, the primary use of medical cannabis among older adults has been to alleviate pain, and more than 30 states now include pain as a qualifying condition for medical cannabis program participation [8]. Four states (e.g., Illinois, New Jersey, New York, Colorado) have gone as far to integrate opioid replacement as a qualifying condition for their medical cannabis programs – allowing for participants to choose medical cannabis as a complement to, or substitute for, taking opioids. Within these contexts, provider attitudes toward the use of cannabis and opioids certainly can be critical in shaping patient choices, and researchers have found a lack of provider knowledge or an unwillingness to discuss cannabis kept older patients from accessing cannabis as a method of pain control [21].
The Public Interest
By 2000, as the leading edge of the baby boom cohort reached and surpassed their 50th birthdays, 34% were in favor of legalizing cannabis, and such favorable attitudes reached 52% by 2014 as more boomers entered older age [7]. Other researchers have found that as general public opinion about cannabis has become less negative, older individuals have become more likely to adopt favorable attitudes [35]. These changing attitudes among older adults also have been tied to perceptions about the medical benefits of cannabis as nearly 60% of persons over the age of 45 years believed cannabis provided a medical benefit and 72% believed doctors should be allowed to recommend medical cannabis [36]. Although such attitudes were higher among those who previously had taken cannabis, nearly two out of every three who never took cannabis at any point during their life also held such favorable attitudes about medical benefits. Similarly, in conducting focus groups across Colorado, other researchers found that a large portion of non-using older adults believed cannabis contributed to positive outcomes based on the reported experiences of loved ones and friends who used cannabis [21]. Health-care providers also seem to hold positive attitudes about cannabis use for medical purposes. In a survey of 1446 readers of the New England Journal of Medicine, researchers [37] found that 76% supported the use of medical cannabis in a case study in which an older woman was diagnosed with metastatic cancer and suffering with nausea and pain.
Both older adults and physicians have indicated the need for information and education about the use of medical cannabis for age-related medical conditions and symptoms, as well as education about methods for consumption, and both groups lament the lack of research on cannabis use [21]. While several provider organizations (e.g., the American Medical Association, American Nurses Association, American Pharmacists Association) have stopped short of endorsing medical cannabis use [8], they all have called for more public education for patients and training for their provider constituencies, with a particular emphasis placed on differentiating the legal risks associated with a doctor prescribing cannabis (i.e., a Food and Drug Administration [FDA] violation) relative to the risks of a doctor discussing or recommending it (i.e., as protected by free speech).
Ultimately, the lack of research and education is problematic, creating a situation in which older adults access potentially unreliable information primarily from nonprofessionals such as dispensary staff, friends, or acquaintances. Given the current context in which medical providers and the health-care systems in which they work may not offer such patient education and provider training, public health officials should consider providing evidence-based, standardized information, education, and training through the national network of Area Agencies on Aging, the National Library of Medicine, and university-based outreach programs.
Concluding Remarks
In this chapter, we explored the rapidly growing intersection between cannabis and older persons. While initial research has been illuminating, we still have a lot more to learn and need more rigorous studies that examine cannabis across the life course and conduct large experimental (basic and clinical) studies that focus exclusively on age-related disorders. Meanwhile, states continue to expand cannabis legalization, and several critical issues remain unclear. Why are some doctors underinformed or discouraged from talking to older patients about medical cannabis? Should insurance coverage be offered to older adults who take a proven cannabinoid as a substitute for opioids? At this time, these sorts of critical public health policy issues cannot be addressed largely because there is a pervasive lack of reliable and representative information being collected about cannabis and older persons.
In looking forward, we see the critical role state governments assume in shaping the intersection between cannabis and older persons. State authorities can support public education; define provider training requirements; monitor the development, distribution, and dispensation of cannabis; and support research that examines these issues. Indeed, American state governments already have extended cannabis program eligibility for several age-specific neurologic and muscular conditions including amyotrophic lateral sclerosis (covered in 16 states), multiple sclerosis (19 states), and Parkinson’s disease (12 states), with little scientific evidence; other states have extended eligibility for persons with terminal illness and support applications submitted by caregivers. As we look to better understand cannabis and older persons, perhaps we should look to state governments for leadership in supporting research, designing evidence-based programs, and protecting older adults.
This effort was supported by the University of Iowa, College of Public Health, and by the Division of Geriatric Medicine, McMaster University.