Medical Cannabis

Taboo for a long time


In many modern societies, marijuana has been a taboo for a long time. However, its medicinal use can be traced back over five thousand years. Over the past few decades, societies have become more open towards cannabis as science unveils its health benefits.


Map of CB1 and CB2 receptors. Click to enlarge.

It was during the 1960s that THC (tetrahydrocannabinol) and CBD (cannabidiol) were first identified and their structures elucidated. Two decades later, in 1988, scientists were able to locate cannabinoid receptors in an animal’s brain, which THC and CBD bind to. Studies continued in the 1990s and the isolation and cloning of the two known cannabinoid receptors, CB1 and CB2, cast a brighter light on the endocannabinoid system. The research on these receptors led to the discovery of endogenous cannabinoids, such as anandamide, which are produced by the human body and bind to CB1 and CB2.

The endocannabinoid system, which consists of several receptors, ligands, and metabolic enzymes throughout the human body, is involved in many different physiological and pathophysiological processes. Endogenous cannabinoids, such as anandamide, play an essential role in regulating this system. THC and CBD act by substituting for these endogenous cannabinoids and connecting with the receptors, CB1 and CB2.

It has been clinically proven that cannabinoids such as THC and CBD are a safe medicine for major health conditions:

  • Antiemetic in the treatment of chemotherapy-induced nausea and vomiting

  • Child epilepsy – treatment of seizures associated with Lennox-Gastaut syndrome or Dravet syndrome

  • Treatment for chronic pain in adults and as an adjunctive therapy for cancer-related pain

  • Muscle spasticity treatment for patients with multiple sclerosis

There is also evidence that cannabinoids are effective for patients with:

  • Anxiety symptoms

  • Appetite and decreasing weight loss associated with HIV/AIDS

  • Fibromyalgia

  • Glaucoma

  • Sleep disturbances associated with obstructive sleep apnea syndrome

  • Symptoms of post-traumatic stress disorder (PTSD)

  • Symptoms of Tourette syndrome


Safety and Side Effects

Like all medication, cannabis products may cause side effects. Most of the known side effects associated with medical cannabis have been extrapolated from studies on recreational users who ingest uncontrolled dosages. Side effects and adverse events associated with cannabis are varied because cannabis affects the endocannabinoid system, which plays an essential role in many physiological processes.

Some of these adverse events are dizziness, fatigue, altered judgment, decreased attention, tachycardia, nausea, vomiting, and appetite and motility changes, and some patients may report increased anxiety. Patients who are especially susceptible and consume cannabis may experience acute psychotic symptoms. For a detailed description of side effects, see Information for Health Care Professionals: Cannabis (marihuana, marijuana) and the cannabinoids ; Section 7.0, Adverse Effects (Health Canada 2013).

A Canadian study called COMPASS (Cannabis for the Management of Pain: Assessment of Safety Study), published in 2015 (Ware et al. 2015), followed 215 medical cannabis patients with chronic pain for one year. Patients had access to a median dose of cannabis, 2.5 g/day containing 12.5% THC. When compared to controls, chronic pain patients not using cannabis, there was no significant increase in serious adverse events and no difference in cognitive function, lung function, haematology profile, or biochemistry, including liver and renal function. There was not a significant increase in serious adverse events but there was a substantial increase in non-serious adverse events. Most commonly reported non-serious adverse events included dizziness, nausea, and fatigue. Despite this, patients had a statistically significant improvement in their levels of pain, symptom distress, mood, and quality of life.

A typical concern among patients is that they may feel “high”, but this in fact should not be a concern as patients can obtain their treatment without experiencing euphoria. Another concern is that patients may develop an addiction. Most people who use cannabis do not develop problems with dependence. Data from recreational use indicates that 9% of adults who use cannabis develop a dependency (Lopez-Quintero 2011). While these levels are similar to reported levels of dependency for anxiolytics (9%), it is important to note that there is not sufficient data on medical cannabis yet, so levels for cannabis may be even lower.



  • Individuals who are severely allergic to cannabis or its constituents.

  • Patients who are pregnant or breastfeeding.

  • Patients who are under the age of 25.

  • Patients who have unstable cardiovascular disease (including unstable angina, unstable arrhythmias, and uncontrolled hypertension).

  • Patients with a history of drug or alcohol addiction should be cautious, although there is evidence to suggest that cannabis can be used as a substitute for these more dangerous substances.

  • Patients with unstable or untreated psychiatric conditions, including bipolar disorder, psychosis, or if actively suicidal. If cannabis is prescribed, they should be monitored by a psychiatrist.