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A Prescription for Cannabis

A growing body of research is examining cannabis’ effects for a variety medical conditions, but several challenges remain that may shape the future of cannabis in Western medicine

Michelle Dotzert, PhD

Michelle Dotzert is the creative services manager for Lab Manager. She holds a PhD in Kinesiology (specializing in exercise biochemistry) from the University of Western Ontario. Her research examined the...

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With widespread legalization and decriminalization of cannabis throughout North America, cannabis is more accessible than ever. However, a pressing question remains: does cannabis have medical value?

With widespread legalization and decriminalization of cannabis throughout North America, cannabis is more accessible than ever.  However, a pressing question remains: does cannabis have medical value?

Cannabis as medicine: examining the evidence

Despite a large body of anecdotal evidence, clinical research evaluating the safety and efficacy of medical cannabis lags behind. There are countless books, websites, and videos devoted to sharing patient experiences with medical cannabis, and recently, Strainprint™ Technologies has released The Canadian Medical Cannabis Experience: A 2019 Patient Retrospective. The report incorporates analysis of real-time anonymous patient outcomes from a mobile journaling app and surveys. 

Several clinical trials have also been completed, with more underway to assess the use of medical cannabis for a variety of conditions. Taken together, the current evidence does not provide a clear, sweeping conclusion regarding the merits of medical cannabis, rather, there is evidence to support its use—or at least further investigation into its effects—for several medical conditions, and a lack of evidence to support its use for other conditions. 


One of the most well-known uses of medical cannabis is as an antiemetic among patients receiving chemotherapy, however only synthetic cannabinoids, dronabinol, and nabilone are FDA approved for this purpose and are administered orally with precisely defined doses and schedules.  Other forms of medical cannabis have been sanctioned by multiple states, but lack dosing information. According to the American Society of Clinical Oncology Clinical Practice Guidelines, updated in 2017, “evidence remains insufficient for a recommendation regarding medical marijuana (cannabis) for the prevention of nausea and vomiting in patients with cancer who receive chemotherapy or radiation therapy.” 

In addition to its antiemetic effects, cannabis may be effective in treating breakthrough pain. Breakthrough pain is a common occurrence among cancer patients, and is often severe with a rapid onset. Treatment with fentanyl buccal tablets is effective, but may also be costly and is associated with a risk of overdose.  PPP001 is an inhalation product containing synthetic THC and CBD (cannabidiol, not associated with psychoactive effects) being investigated as an alternative for managing breakthrough pain. Other trials will examine the efficacy of varying concentrations of THC and CBD for symptom management among cancer patients. 


Dronabinol is also FDA approved for the treatment of weight loss among patients with AIDS. Ongoing research will examine whether cannabis may be used to manage HIV-associated distal sensory neuropathies, thought to result from immune system dysregulation, and antiretroviral toxic neuropathies associated with exposure to reverse transcriptase inhibitors.  A clinical trial examining the effects of smoked cannabis (3.56% THC) on neuropathic pain of HIV-associated sensory neuropathy has shown a beneficial effect. Another trial is underway to examine the safety and tolerability of oral capsules containing different ratios of CBD and THC among individuals living with HIV.

Multiple Sclerosis

Multiple Sclerosis (MS) is an autoimmune disease affecting the central nervous system, and symptoms include spasticity, neuropathic and musculoskeletal pain, tremors, bladder problems, and cognitive changes, among several others. The effects of THC have been more thoroughly investigated in the context of MS compared to some other conditions. 

The Cannabinoids in Multiple Sclerosis study was one of the largest randomized controlled trials to examine the effects of dronabinol and cannador (a natural cannabis extract containing THC and CBD) on spasticity. The results were mixed—physician-administered tests demonstrated no improvements associated with either treatment, however, patients reported improved spasticity and sleep. In the Multiple Sclerosis and Extract of Cannabis trial, patients receiving oral cannabis extract reported relief from muscle stiffness and spasm, and improved sleep. Nabiximols (Sativex) is a plant extract of C. sativa containing THC and CBD, and is approved in Canada, the United Kingdom, Denmark, and several other countries for the treatment of spasticity associated with MS.

Alzheimer’s Disease

Research suggests the ECS is altered among Alzheimer’s patients, and it is being investigated as a potential therapeutic target. CB1 and CB2 receptor activation has been shown to reduce β-amyloid peptide action and promote intrinsic repair mechanisms in experimental models of Alzheimer’s Disease (AD). 

Clinical research aims to investigate whether THC may improve some of the symptoms of AD, including agitation, anxiety, insomnia, aggression, etc. Studies have shown positive effects of dronabinol for reducing anorexia, disturbed behavior, and nighttime agitation among AD patients, as well as improving circadian rhythms. Conversely, oral THC has been shown to be well-tolerated, but was not associated with a significant reduction in neuropsychiatric symptoms.  

Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic condition that encompasses both Crohn’s disease, characterized by inflammation of the digestive tract, and ulcerative colitis. The effects of cannabis on suppressing symptoms and inhibiting the inflammatory reaction is thought to be mediated through activation of cannabinoid receptors in the gut.

A retrospective observational study reported treatment with combined THC and CBD oil significantly reduced disease index, as well as the need for other medication and surgery. Many IBD patients also report a perceived benefit of cannabis for symptom relief. Of patients considered lifetime cannabis users surveyed at a tertiary-care outpatient clinic, 33 percent of those with ulcerative colitis, and 50 percent of those with Crohn’s disease reported use for symptom relief. Similarly, a prospective cohort study carried out at an academic medical center found that 12.3% of patients with IBD were active cannabis users, 39 percent were past users, and among both groups, 16.4 percent found marijuana was helpful for symptom relief.

This is merely a small selection of research pertaining to medical cannabis. There are numerous other completed trials, and many more scheduled to begin. At present, it may appear that the anecdotal evidence outweighs the clinical evidence, however this should not be taken as a sign that medical cannabis is ineffective. Rather, it demonstrates an urgent need for ongoing scientific investigation.