Medical Cannabis for the Treatment of Dementia: A Review of Clinical Effectiveness and Guidelines

Dementia refers to a set of symptoms and signs associated with a progressive deterioration of cognitive functions that affects daily activities.¹ Symptoms may include memory loss and difficulties with thinking, problem-solving or language, as well as changes in mood, perception, personality, or behaviour.^2,3 According to the World Alzheimer Report 2018, about 50 million people worldwide lived with dementia in 2018, with the number projected to increase to 152 million by 2050.⁴ In Canada, the estimated number of people living with dementia in 2016 was 564,000, and this is expected to increase to 937,000 by 2031.⁵ The total health care system costs and out of pocket costs of caring for people with dementia were $10.4 billion in 2016, and are projected to double by 2031.⁵ Alzheimer’s disease is the most common type of dementia, accounting for about two thirds of all dementia.⁴ Other types of dementia that occur less frequently include vascular dementia, mixed dementia, Lewy body dementia, frontotemporal dementia, and young-onset dementia.^1,3 Neuropsychiatric symptoms (NPS) are common to all dementia types and may manifest as agitation, aggression, wandering, apathy, sleep disorders, depression, anxiety, psychosis, and eating disorders.³ These behavioral symptoms of dementia present significant risks of injury to the patients and caregivers, reduce quality of life, and may cause distress or depression. The progressive course of dementia cannot be altered since there is no known cure or disease-modifying therapy.⁶ However, there are interventions to manage NPS, although they are based on limited and disparate evidence.³ The first-line treatment of NPS comprises a range of nonpharmacological interventions based on identifying unmet physical and emotional needs, such as inadequately treated pain and unpleasant environmental factors, which may trigger the symptoms. Pharmacological therapies are the second-line treatment in patients for whom nonpharmacological interventions were unsuccessful and who present a potential risk of injury to either themselves or others. Pharmacological interventions commonly involve off-label use of atypical antipsychotics or second-generation antidepressants, usually in combination the nonpharmacological strategies.³ Given the limited currently available therapeutic options, their side-effect profiles, and inconsistent evidence base, there is a need for alternate therapies in the growing population of dementia patients.^7–9 Medical cannabis has been investigated as one the potential alternative treatments for dementia.^10,11 Cannabis (also known as marijuana) is a plant that contains over 70 different chemical compounds called cannabinoids.² Although their mechanism of action in dementia is not well elucidated, they have been shown to interact with neurotransmitter systems that have been implicated in the manifestations of NPS.¹¹ Currently, patients living in Canada who have a prescription from an authorized health care professional can legally use cannabis for medical purposes, if they are registered with a licensed producer or Health Canada.^12,13 The objective of this report is to summarize the evidence regarding the clinical effectiveness of medical cannabis for the treatment of dementia and the evidence-based guidelines for its use in this condition.