Weeding through the Published Support for Cannabis-based Health Effects

A review of the current state of literature-supported health claims points to cannabis-based neurological applications as the early front runners.

Cannabis has been linked to many health and potential therapeutic applications. It is known that the endocannabinoid system is integrated into neural, immune, inflammatory, digestive, and other physiological pathways. The major cannabinoids, delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), have affinity toward endocannabinoid receptors, primarily CB1 in the case of THC and CB2 for CBD, thereby modulating signalling and multi-system function.

Beyond this lies a bounty of both scientifically sound and anecdotal evidence as to the effects of THC, CBD, and other cannabis compounds on diverse health conditions ranging from epilepsy, to multiple sclerosis, to cancer. A review of the current body of published literature, both research and clinical, is critical in understanding cannabis-based health effects and the prospects for therapeutic development.

A 2017 report by the National Academies on the Health Effects of Cannabis cited the following conclusions. This report was based on a comprehensive literature assessment by multiple members of the review committee as to the quality and risk of bias of the research conclusions. The analysis included reporting of the questions of interest prior to literature search to minimize confirmation bias. Regardless of the rigorous methodology, it is acknowledged that some relevant findings were inadvertently missed, as the large amount of information and the limited time frame undoubtedly left some details uncovered.

The Weight of Evidence Categories

Conclusive evidence of therapeutic effects - Strong evidence from randomized clinical trials (RCTs) to support conclusions that cannabis or cannabis compounds are effective for a specific health indication.

Conclusive evidence for other health effects – Strong evidence from RCTs to support a statistical association between cannabis or cannabis compounds and a specific health indication. This level of evidence includes strong supportive evidence, the absence of strong refuting evidence, and robust statistical significance.

Substantial evidence of therapeutic effects – Strong evidence to the support conclusions that cannabis or cannabis compounds are effective for treatment of a specific health indication.

Substantial evidence for other health effects – Strong evidence to support a statistical association between cannabis or cannabis compounds and a specific health indication.

Moderate – Some evidence; Limited – Weak evidence; Insufficient – No association.

There is Conclusive or Substantial evidence that cannabis or cannabinoids are effective:

  • For the treatment of chronic pain in adults (cannabis)
  • For the treatment of chemotherapy-induced nausea and vomiting (oral cannabinoids)
  • For improving patient-reported multiple sclerosis spasticity symptoms (oral cannabinoids)

There is Moderate evidence that cannabis or cannabinoids are effective for:

  • Improving short-term sleep outcomes in individuals with sleep disturbance associated with obstructive sleep apnea syndrome, fibromyalgia, chronic pain, and multiple sclerosis (cannabinoids, primarily nabiximols)

There is Limited evidence that cannabis or cannabinoids are effective for:

  • Increasing appetite and decreasing weight loss associated with HIV/AIDS (cannabis and oral cannabinoids)
  • Improving clinician-measured multiple sclerosis spasticity symptoms (oral cannabinoids)
  • Improving symptoms of Tourette syndrome (THC capsules)
  • Improving anxiety symptoms, as assessed by a public speaking test, in individuals with social anxiety disorders (cannabidiol)
  • Improving symptoms of posttraumatic stress disorder (nabilone)

There is Limited evidence of a statistical association between cannabinoids and:

  • Better outcomes (i.e., mortality, disability) after a traumatic brain injury or intracranial Hemorrhage.

The findings of this analysis fall inline with the views of many experts in the field. For example, expert panelists at the 2016 Marijuana and Cannabinoids: A Neuroscience Research Summit meeting sponsored by the NIH offered their assessment of various medical implications of the cannabis field. Not surprisingly, there were agreements as to the effectiveness of cannabinoids in controlling symptoms of multiple sclerosis, specifically spasticity and central pain. In addition, it was agreed that cannabinoids including THC and CBD have been clearly shown to suppress pain through CB1 and CB2 modulation, in some cases via similar pathways as endocannabinoids.

Of course, there were agreements as to statistically insignificant correlations between cannabinoids and other health indications such as cancer, either causative or therapeutic. Alas, all parties appear to agree that high quality research and well-controlled randomized clinical trials are required to further substantiate support or to refute the therapeutic value of cannabis for the wide spectrum of potential conditions. It will be exciting to witness the true therapeutic value of cannabis as new conclusions come to light.

Beyond academic research and published clinical studies, private labs are pushing forward with their own research into therapeutic potential. Included are ongoing clinical trials reporting on the application of cannabinoids for numerous indications, ranging from epilepsy to Crone’s disease, and products ranging from topical patches to chewing gum.

Thus, cannabis-based medicine is advancing on multiple fronts, promising to make this emerging science dynamic and exciting for years to come.