Use of medicinal cannabis in older people is increasing. Despite increased risk of side effects due to age-related physiological changes, benefits may outweigh the risks for some, especially when symptoms are not adequately controlled by conventional treatments due to side effects or suboptimal efficacy.
Quick Summary
Evidence for the efficacy and safety of medicinal cannabis in older people is limited.
The risk of side effects from medicinal cannabis is increased in older people due to their impaired metabolism, decreased reserves, higher potential for interactions with other medicines, and contraindications with existing medical conditions.
Medicinal cannabis may provide benefits in some older people, such reducing opioid use in pain management.
It is important to involve both the older person and their families in clinical decisions regarding medicinal cannabis to facilitate shared decision making.
What Is Medical Cannabis
Medicinal cannabis is a medicine that is derived from the cannabis sativa(marijuana) plant. These medicines contain numerous chemicals known as cannabinoids, including THC (delta-9-tetrahydrocannabinol), and cannabidiol (CBD), with neuroprotective, anticonvulsive, antiemetic, and anti-inflammatory effects.1
Australias Oldest Population
Australia’s population is ageing due to increasing life expectancy and declining fertility rates. As of 30 June 2020, there is an estimated 4.2 million older Australian (aged 65 and over), comprising of 16% of the Australian population. This number is expected to experience continued growth, with projections of 21–23% of the total population by 2066.2
Use of Cannabis Among Older People
Use of medicinal cannabis in older people is increasing.3 Cannabis use among Australians aged 60 and over experienced significant increases between 2016 and 2019 (from 1.9% to 2.9%).4 In the US, the prevalence rate for past cannabis use was 9% among people aged over 50 years and 2.9% for those aged over 65 years between 2015 and 2016.5 Higher prevalence has been reported in other parts of the world, such as in the Netherlands, where more than a third of medicinal cannabis users were aged 60 and over between 2003 and 2010.6
A 2018 scoping review of literature between January 2000 and December 2017 found that marijuana users within the older population (aged 50 years and over) tended to be male, unmarried, have multiple chronic medical conditions, have psychological stress, used prescription medicines and other substances such as alcohol and tobacco.7
There may be many reasons why older people would consider using medicinal cannabis. Many older people may already have familiarity with cannabis, having used it recreationally since the 1970s hippie movement. Some older people may have symptoms not adequately controlled by their current treatments, either due to unwanted side effects or suboptimal efficacy. Older people may also have the perception that cannabis is a plant product that is natural and is less harmful than prescription medicines.8
How Does Medical Cannabis Works?
Cannabinoids such as THC and CBD act on two receptors (CB1 and CB2) that are found throughout our body as part of the endogenous cannabinoid system (ECS). Both receptors are found in the central nervous system, with CB2 also found in the immune system.1
Interest in medicinal cannabis as a potential treatment option for many conditions have increased in recent years, with particular interest for older people who may experience symptoms such as chronic pain, sleep disturbances, cancer-related symptoms, and mood disorders. These symptoms are often poorly controlled by conventional treatment options that cause multiple side effects, making medicinal cannabis a suitable alternative.8
Conventional treatments for conditions common among older adults, such as chronic pain, Parkinson’s disease, depression, and sleeping disorders can have serious side effects, leading to negative health outcomes.9 For instance, non-steroidal anti-inflammatory drugs (NSAIDs) for pain and inflammation is associated with gastrointestinal bleeding, renal impairment, and cardiovascular events, while opioids can cause constipation, nausea, vomiting, drowsiness, and anticholinergic effects.10 Sedative hypnotics for sleeping disorders can cause psychomotor impairment, dizziness, confusion, and increased risk of falls, which is particularly critical in older people.11
What Does The Evidence Say?
Evidence for the efficacy and safety of medicinal cannabis in older people is limited. The average age of patients for a majority of published clinical studies of medicinal cannabis is 40–60 years, with no subgroup analysis performed for older patients in these studies.8 Table 1 (see below) summarises the currently available evidence.
Medical Cannabis For Pain And Cancer
A 2018 prospective study evaluated the efficacy and safety of 6 months medicinal cannabis treatment in 2736 Israeli patients aged 65 years and over (mean age 74.5) between January 2015 and October 2017. The most common indications were pain (66.6%) and cancer (60.8%). Adverse effects were dizziness (9.7%) and dry mouth (7.1%). The study concluded that therapeutic use of cannabis was safe and effective in this older population. Furthermore, it may decrease the use of other prescription medicines, including opioids (the study reports that 18.1% discontinued opioid use or reduced dose).12
Medical Cannabis for Agitation in Alzheimer’s disease
A 2019 randomised, placebo-controlled trial of nabilone (a synthetic cannabinoid that mimics THC) for agitation in Alzheimer’s disease (mean age 87) reported significant improvements in agitation, neuropsychiatric symptoms, and caregiver distress compared with placebo, although a higher incidence of side effects was observed.13
Medical Cannabis for Anorexia and Behavioural Symptoms in Dementia
A 2014 systemic review investigating safety and efficacy of medicinal cannabis in older people aged 65 years and over included results from five randomised controlled trials with a total of 267 patients (mean age 47–78 across all trials). It concluded that THC was likely to be useful for treatment of anorexia and behavioural symptoms in dementia in this older population. Adverse events were more common when compared with placebo, with sedation, dizziness, and somnolence being the most frequently reported side effects.1
Medical Cannabis for Parkinson’s Disease
A 2014 exploratory double-blinded trial of CBD in patients with Parkinson’s disease (mean age 65.9) reported significant improvement in overall function and well-being scores relative to placebo.14
Safety and Pharmacokinetics of THC in Older People
A 2014 randomised, double-blinded, placebo-controlled phase 1 trial evaluated the safety and pharmacokinetics of THC in healthy older people (65 years and over). It found that THC was safe and well tolerated, with the most frequently reported side effects were drowsiness (27%) and dry mouth (11%). Plasma concentrations of THC had wide inter-individual variability, which were consistent with previous studies in younger people. However, pharmacodynamic effects (the body’s biological response to medicines) of THC were smaller than those seen in young adults. Possible explanations include age-related physiological changes such as delayed gastric emptying time, and decreased gastrointestinal mobility and absorption, which could affect overall absorption and bioavailability of THC.15
Similar results were observed in a 2015 randomised, double-blinded, placebo-controlled, crossover trial of THC in older patients with dementia (mean age 77.3). Pharmacodynamic effects and side effects were minor, with inter-individual variation in pharmacokinetics.16
Is Medical Cannabis Safe For Older People?
The risk of side effects from medicinal cannabis is increased in older people due to their impaired metabolism, decreased reserves, higher potential for interactions with other medicines, and contraindications with existing medical conditions. Areas that are pertinent to older people include effects of medicinal cannabis on:8
psychomotor function
cognition
cardiovascular risks
mental health.
Major side effects of medicinal cannabis pertinent to older people
The most prevalent adverse effects of medicinal cannabis, particularly THC, relates to psychomotor function and cognition. As most medicinal cannabis products contain at least some amount of THC, these effects are important to consider in older people, especially those with existing mild cognitive impairment or dementia.8 These effects may also predispose older people to falls and injury, especially when used with other psychotropic medicines, such as medicines for sleep, depression, and anxiety.18
Implications for Opioid Use
Problematic use of opioids by older people are associated with many side effects, such as sedation, cognitive impairment, falls, fractures, and constipation.24 A recent systemic review of 23 randomised controlled trials of opioids for musculoskeletal pain in older people found only a small effect on decreasing pain intensity, but with a three times higher rate of side effects and four times higher odds of treatment discontinuation due to side effects. The authors concluded that the risks of using medicinal cannabis may outweigh the small benefits of opioid treatment.25
It has been reported that 18.1% of older people (aged 65 years and over) who used medicinal cannabis for pain discontinued opioid use or decreased their opioid dose.12 This opioid-sparing effect of medicinal cannabis may be an instrumental tool in reducing opioid use in pain management for older people.26
Recommendations for Medicinal Cannabis Use in Older Patients
Medicinal cannabis use in older people should be tailored to the individual patient, taking into account each patient’s unique characteristics, such as:8
symptoms or condition requiring treatment
symptom severity
pre-existing medical conditions
possible side effects.
Treatment initiation is recommended to “start low and go slow”, titrating the dose slowly over time until the desired effect is achieved or until the negative effects start outweighing the positives. An initial dosing of once daily at night is recommended minimise daytime psychoactive effects.8 Variables that may affect the dose include:27
body weight
medical condition being treated
body chemistry
amount of medicinal cannabis in the specific product.
Although there is limited data on the ideal strain of medicinal cannabis, administration method, or dose for older people, smoking dried cannabis is not recommended due to reduced lung capacity with age, while inhalation via a vaporiser is suggested to be safer. The preferred route of administration for older people is likely to be oral ingestion, such as a medicinal cannabis oil, due to a more prolonged and stable pharmacokinetic profile.8
Although plant-derived preparations may have the potential advantage of the entourage effect (the effect when multiple compounds in the plant synergistically work together to increase the overall effect), amounts of THC and CBD are variable. If a plant-derived product is chosen, a strain with higher CBD (10–20%) and lower THC (<2%) is preferred.8
It is important to involve both the older person and their families in clinical decisions regarding medicinal cannabis. Open discussion and informative conversations with the doctor will facilitate shared decision-making. Consider the risk and benefits that pertain to the individual patient. For instance, patients in palliative care may be more willing to take more risks to improve their quality of life compared with patients with longer life expectancies.8
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