Canadians physicians, like most Canadian citizens, hold highly polarized views regarding cannabis. Doctors tend to be all for or completely against cannabis, with few taking a nuanced view of both the risks and the potential benefits. To fulfill our duty to protect, promote and restore health, we must become informed leaders, not reluctant followers or reckless zealots.
Some physicians are writing thousands of cannabis prescriptions every year for a wide variety of maladies. Many of their "patients" are not adequately assessed, nor are they informed about or encouraged to try conventional treatment options, which often have far more evidence for their safety and efficacy. Their "patient" wants cannabis and they get cannabis.
Other physicians believe cannabis is completely without merit. They don't know how to prescribe or access it, and they haven't critically evaluated the evidence supporting the use of cannabis for some medical conditions. To these doctors, cannabis is an illegal, dangerous, addictive drug and any physician prescribing it is a bad doctor.
Neither view is particularly helpful or appropriate. Medicine is rarely so black and white. There is alive and there is dead and everything else in medicine is open to interpretation, colored by our experience and personal biases, and affected by the unique biology of each individual we treat.
Practicing modern medicine means striving to make "evidence-based" decisions. Such evidence should come from well structured, bias-free, clinical trials that prove that one treatment is superior to another. In reality, no treatment possesses flawless, irrefutable evidence.
Clinical trials often recruit "pristine patients" who suffer only from the illness being studied. Study subjects usually don't have multiple illnesses, drug abuse or other problems that would exclude them from most clinical trials. "Real world" patients are rarely so straightforward. Consequently, we can infer from research how a drug might affect our patient, but it is far from certain that a drug will perform in the real world the same way it did in a trial.
Furthermore, research evidence may be interpreted differently, depending on the reader. For instance, doctors generally agree that research clearly demonstrates the life-saving benefits of cholesterol-lowering drugs, called statins. However, statins also cause significant side effects for some patients, including muscle pain. For some doctors, it's a no-brainer: statins save lives. While some patients experience muscle pain, the benefits clearly outweigh the risks and statins should be prescribed for most patients with high cholesterol. For other doctors, it's a no-brainer: statins save lives but the side effects are sometimes intolerable and statins should be reserved for the minority of patients. This is "evidence-based" medicine, but how the evidence is interpreted varies widely.
Despite the flaws, research evidence remains our best tool in determining what treatments to offer our patients. The strongest evidence comes from clinical trials where the study drug is compared to another drug that has already been proven to be effective, as well as a placebo.
Study subjects must be appropriately randomized, which means they are randomly assigned to receive the study drug, the comparator drug or the placebo. The only difference between the groups should be the treatment they receive. Every subject must be assessed the same way, regardless of the treatment.
Randomization is essential to reduce bias and allows researchers to conclude that the differences found between treatment groups are due to the treatment and not due to other factors like the subject's age, sex or ethnicity. If 90% of the subjects receiving a study drug are white, elderly males and 90% of the subjects receiving the placebo are Asian teenaged girls, the groups are inadequately randomized, thus too dissimilar to allow a fair comparison.
Appropriate randomization in clinical trials also facilitates "blinding", which means no one knows which treatment a subject is receiving. When the subject and every individual that interacts with the subject are blinded, the study is considered "double-blind". Un-blinded trials (AKA open-label trials) have a heightened risk of bias, rendering the data far less reliable. There must also be an adequate number of subjects included in a study to be able to show a meaningful difference between treatments and placebo.
The highest quality studies are randomized, double-blind, placebo-controlled trials, and are required for a drug to be approved by Health Canada and other regulatory agencies.
Unfortunately, there are very few high-quality studies for medicinal cannabis. Studies often differ in terms of the type, source, and dose of cannabis, making them difficult to compare. Most cannabis studies are "open-label", lack a placebo or another drug comparator or have too few subjects to demonstrate the value of the treatment. This makes it extremely difficult for doctors to determine whether cannabis is a safe or effective treatment to offer patients.
The best quality evidence for medicinal cannabis is for chemotherapy-induced nausea. Pain management evidence is less robust. For mental illnesses, there is poor quality data supporting cannabis treatment and more evidence demonstrating the harms.
Physicians must consider the evidence. It is not acceptable to prescribe a drug simply because it helped another patient. Drugs that lack high-quality evidence, like cannabis, should be reserved for patients who are suffering, and for whom conventional treatments have failed.
The treatment of post-traumatic stress disorder (PTSD) is a good example. I have patients who were prescribed cannabis for this serious, sometimes deadly, condition without being urged to try treatments with high-quality evidence that demonstrates both safety and efficacy, including psychotherapy and medications. I also have patients with PTSD who didn't benefit from treatments that have solid evidence and cannabis ultimately provided real relief.
Some patients who haven't responded to conventional treatments will benefit from cannabis; however, we need more evidence before widespread medicinal use is defensible. We need education and treatment guidelines, so doctors develop confidence prescribing cannabis appropriately. Treatment guidelines underscore the most robust evidence and focus attention on areas where the evidence is lacking.
Legalization is coming. More Canadians will be turning to cannabis to manage a variety of illnesses. Physicians must be prepared to provide credible, responsible guidance.
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