Medical cannabis in a lab

Medical Cannabis


Written by: CDHF

Updated: November 8th, 2022

For the Health Care Professionals Guide, click here. 


Recently, there has been a surge of attention on medical cannabis. The Canadian Digestive Health Foundation is excited about the possibility of increased research on the medicinal uses and safety of cannabis, which legalization will make more accessible.

Whether you are already authorized to use medical cannabis by your healthcare professional, or are considering it as a therapy, it’s important to understand the medicine and its effects so you can navigate the methods of administration, product selection, and dosing.

How Cannabis Works in the Body

Cannabinoids are the main active ingredients in cannabis and more than 100 have been identified. They can be produced by the human body, found in plants, or manufactured in a laboratory for use in some prescription medications. Here, we will focus on cannabinoids found in the cannabis plant, called phytocannabinoids.

Phytocannabinoids are concentrated in sticky crystals on the flowers of the female cannabis plant, called trichomes. These trichomes are separated from the plant material when making extracts, including cannabis oil.

THC (delta-9-tetrahydrocannabinol) and CBD (cannabidiol) are the two most-researched and well-understood cannabinoids. Cannabis varieties (also known as strains) differ in their THC and CBD levels and in the ratio of THC to CBD. Therapeutic benefits will vary depending on a patient’s biology and the variety selected.


The limited research shows that THC may be helpful for things such as pain relief, relief from nausea, reduction of spasticity, and improving appetite. THC is also responsible for the euphoric or the psychotropic effects of cannabis.


The limited research into the CBD suggests that it may be helpful for reducing inflammation, seizures, and anxiety and improving sleep. It does not cause the intoxicating, euphoric effects that can be caused by THC and may in fact, reduce some of the potential side effects of THC, such as nervousness.

Cannabis isn’t a one-size-fits all therapy, so finding an appropriate variety is often a matter of informed trial and error. Many patients benefit from using more than one product as for example, when they are medicating during the day versus the evening, or for different symptoms.

Activation of Cannabinoids

To be effective, cannabinoids need to be heat-activated in a process called decarboxylation. This occurs during smoking or vaporizing when the plant matter is heated to at least 120C. Cannabis oil and softgels from licensed producers contain cannabis oil that has been decarboxylated.

Indica and Sativa 

The terms “indica” and “sativa are botanical terms that describe the shape of the different cannabis plants. They are often used to characterize the range of possible effects from a variety of cannabis.

Some people use “indica” to describe a variety whose effects are more sedating or physical in nature. Some people use “sativa” to describe a variety whose effects are more cerebral or energizing. 

The Endocannabinoid System

Humans naturally produce cannabinoids (called endocannabinoids) that interact with cell receptors throughout the body. Endocannabinoids are like a key, receptors are like a lock, and they fit together to produce effects in the body. This endocannabinoid system (ECS) is involved in many physiological functions, including inflammation, sleep, pain, memory, digestion, immune function, neuroprotection, and more.

The phytocannabinoids (eg. THC and CBD) that are produced by the cannabis plant also interact with the receptors of your ECS. This could partly explain why cannabis seems to have such an effect on such a wide variety of symptoms and conditions.

Methods of Administration & Finding the Right Dose

Ways of using cannabisWhen effects could beginHow long effects could last 
Smoking/vaporizingSeconds to minutesUp to 6 hours*
Swallowing (food/capsules)30 minutes – 1.5 hoursUp to 12 hours*
Under the tongue5-30 minutesUp to 12 hours*
*some effects could last as long as 24 hours

Start Low, Go Slow


When you first try vapourizing cannabis, or if you are trying a new variety, start with 1 inhalation and wait 15 minutes before consuming more. Increase by 1 inhalation every 15-30 minutes until optimal dose is achieved. Observe how your symptoms are affected and how your mind and mood feel, before deciding to take more.


It’s even more important to start low, go slow when ingesting cannabis. Consult the dosing guidance on your product, and if you are unsure you should call your medical cannabis provider or healthcare professional for guidance.

Product Forms

Dried Flowers

Dried cannabis is typically offered as either dried whole flowers (“bud”) or milled (“prepared” or “ground”). Whole flowers from the female cannabis plant are harvested, the stem and leaves are trimmed, and then the flowers are dried to a specific moisture content. Milled cannabis contains the same active ingredients as dried whole flowers and is ready for use in a vapourizer. 

Cannabis Oil

Concentrated cannabis resin, containing cannabinoids and other active compounds, is extracted from cannabis flowers that have undergone thermal decarboxylation to make a product for you take orally from a syringe. This allows you to know exactly how much THC and CBD you are taking in each dose.


Softgels are filled with cannabis resin dissolved in food-grade carrier oil. They offer you a convenient and discreet option for your medication. Softgels may only be available from certain licensed producers of cannabis.

Clinical Data to Date

The Use of Medical Cannabis in Gastroenterology 

Research into the therapeutic efficacy of cannabis, its extracts, and refined phytochemicals has been an active area of study for over 40 years and is accompanied by a vast amount of anecdotal evidence and case reports of therapeutic benefit. The list of conditions that medical cannabis is alleged to treat continues to grow, but research is still lacking in many areas.

Although many patients report that it alleviates their symptoms, it remains unclear whether cannabis and its extracts are effective for treating GI conditions. Two major limitations to designing proper clinical studies are regulatory licensing hurdles and the lack of development and supply of a true placebo.

Despite a lack of high-quality evidence due to regulations, some research indicates that medical cannabis may improve GI conditions such as severe nausea, inflammatory bowel disease (IBD), and chronic pain.

Inflammatory Bowel Disease (IBD) 

There is currently a large unmet need in the treatment of inflammatory bowel disease (IBD) with conventional medical therapy. Despite improvement in disease activity, many patients have persistent clinical symptoms that have significant impact on their quality of life. Patients have been seeking out alternative therapies (including cannabis) to help manage persistent symptoms associated with IBD (J.K., 2018).

Surveys of cannabis use in IBD patients in the United States and Canada have found that approximately 15% to 20% of patients currently use cannabis, and up to 40% have tried cannabis to relieve IBD symptoms. 

These retrospective studies have shown that many IBD patients report cannabis improves symptoms such as pain, appetite, and diarrhea. In these studies, patients have used cannabis by both oral an inhalation routes (J.K., 2018)

Crohn’s Disease:

A small study was designed to determine if cannabis (smoked) could induce remissions in Crohn’s disease patients who were unresponsive to steroids, immunomodulators, or anti-TNF agents (Naftali et al. 2013). Clinical response was seen in 10 of 11 patients in the cannabis group compared to 4 in 10 in the placebo group. Three patients in the cannabis group were weaned from steroid dependency. Those receiving cannabis had improved appetite and sleep and no significant side effects.

Recently, in the first study of its kind, cannabis oil has been shown to significantly improve the symptoms of Crohn’s disease and the quality of life sufferers but, contrary to previous medical thinking, has no effect on gut inflammation (Naftali, et al 2018).

In this randomized, placebo-controlled study, researchers from Israel have shown that cannabis can produce clinical remission in up to 65% of individuals after 8 weeks of treatment, but that this improvement does not appear to result from a dampening down of the underlying inflammatory process. Going forward, the research group plans to explore the potential anti-inflammatory properties of cannabis in the treatment of IBD further.

Recently, Dr. Naftali stated “There are very good grounds to believe that the endocannabinoid system is a potential therapeutic target in Crohn’s disease and other gastrointestinal diseases,” “For now, however, we can only consider medicinal cannabis as an alternative or additional intervention that provides temporary symptom relief for some people with Crohn’s disease.’ (Naftali, et al 2018)

Ulcerative Colitis:

Irving and colleagues assessed the efficacy, safety, and tolerability of once-daily oral CBD-4% THC (CBD-rich extract) for 10 weeks in patients with active ulcerative colitis (N=60) as an adjuvant therapy while on stable dosing of mesalamine therapy. Patients were less tolerant to the CBD-rich extract than placebo, and there were significant protocol deviations in the study. Both groups failed to reach the primary endpoint of clinical remission, and there were no differences in the rates of remission between the groups (28% for the CBD-rich extract and 26% for placebo). Per-protocol analysis showed improvement in patient’s global impression of change and a trend toward improved quality-of-life scores with CBD-rich extract use.

Most recently, unpublished data were presented by Naftali and colleagues at the 2018 Digestive Disease Week. They evaluated the effects of smoking 2 cannabis (THC-rich) cigarettes daily or placebo for 8 weeks in patients with moderate to severe ulcerative colitis (N=28). In this study, medical cannabis use was associated with improved clinical disease activity scores and endoscopic improvement (reduction of Mayo endoscopic subscore from 2 to 1; P <.01). However, there was no significant change in CRP or fecal calprotectin in either group.

Other GI Disorders & Symptoms

The potential use of medical cannabis for pain management is also of great clinical interest. It is promising that vaporized cannabis augments the analgesic effects of opioids and cannabinoids and can reduce the dose of opioids used by chronic non-cancer patients (Lynch and Clark 2003; Abrams et al. 2011).

Further, it has been shown to help those with nausea and vomiting. For instance, a review of 28 studies that included 1,772 participants suffering from chemotherapy-induced nausea and vomiting found a greater benefit of cannabinoids for the treatment of nausea and vomiting than an active comparator or placebo (Whiting et al. 2015).

The evidence for treating IBS specifically is sparse at this time. We’re beginning to see clinical experience suggesting effectiveness at reducing diarrhea and relieving abdominal pain, but more research is needed in this area.

Side Effects & Safety Tips

Short-term side effects can include:

Frequent use over a long time can: 

*Remember, if you’ve determined inhalation is right for you, always use a vapourizer to minimize exposure to harmful compounds produced by combustion. This will minimize risks of long-term use.

Safety Tips:

Medical cannabis is not recommended for patients:

If you have any health issues, are using cannabis for medical purposes, or have questions about the effects of cannabis on your health, you should speak with your healthcare professional.

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