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November 17, 2018 In Interests

Clearing the Smoke – Scientific Conclusions About the Medical Effects of Cannabis

Photo courtesy of Alexandre Chambon @goodspleen

 

With cannabis now legal in Canada, many people have an interest in the substance’s effects on health, both good and bad. Many scientific studies have been conducted over the years examining the health benefits of cannabis use for conditions such as chronic pain, multiple sclerosis, or cancer. While individual studies looking at the health effects of cannabis on the same condition may have differing results, we can make conclusions based on systematic reviews, which are academic articles that compile and review all of those individual studies with the goal of providing evidence for or against the effectiveness of a treatment.

For example, a 2011 systematic review looking at the effectiveness of cannabinoids for chronic pain (not including cancer pain) reviewed 18 articles on the topic and concluded that cannabinoids are a safe, but only moderately effective treatment for chronic, non-cancer-related pain1. For those of you interested in better understanding how systematic reviews work, I have included a link to the article in the references section at the foot of this article.

The current holy grail of research on the medical effects of cannabis is a report published in 2017 by The National Academies of Sciences, Engineering, and Medicine2. The comprehensive report includes conclusions regarding evidence for cannabis providing various health benefits. I will outline some of the report’s key findings, but I encourage you to use the link in the references section to see their conclusions for yourself. Please note that these conclusions are merely what the current research tells us, and are subject to change as further research is conducted. With cannabis now legal in Canada, it is less difficult for scientists to conduct studies, so I predict we will learn a great deal more about the medical effects of cannabis in the future. There is still much we do not know.

 

Benefits:

 

  • Conclusive/substantial evidence for:
    • Treatment of Chronic Pain
    • Antiemetic (effective against vomiting and nausea) for chemotherapy patients
    • Improving patient-reported multiple sclerosis spasticity (note: limited evidence for improving clinician-measured multiple sclerosis spasticity)
  • Moderate evidence for:
    • Improving short-term sleep outcomes in people with sleep apnea, fibromyalgia, chronic pain, and multiple sclerosis
  • Limited evidence for:
    • Increasing appetite and decreasing weight loss
    • Improving clinician-measured multiple sclerosis spasticity
    • Improving anxiety symptoms
    • Improving PTSD symptoms
  • Insufficient/insubstantial evidence for:
    • Treating cancers
    • Treating epilepsy
    • Treating irritable bowel syndrome symptoms
    • Improving cachexia and anorexia nervosa
    • Improving ALS (Lou Gehrig’s Disease) symptoms
    • Improving motor symptoms, as in Parkinson’s disease

Adverse Effects: Please note that many of these conclusions are based on statistical correlations. For example, when it is noted that cannabis users observe an increased incidence of suicide, it does not mean smoking cannabis will make you suicidal; rather, it means there is a statistical association between cannabis use and suicides.

 

  • Conclusive/substantial evidence for:
    • Increased risk of motor vehicle accident
    • Decreased offspring birth weight (for maternal cannabis smokers)
    • Worsened respiratory symptoms (long-term users)
    • Higher frequency of bronchitis (long-term users)
    • Development of schizophrenia (with highest risk for highest frequency users)
  • Moderate evidence for:
    • Incidence of lung cancers and cancers of the head and neck
    • Increased risk of overdose-related injuries, such as respiratory distress
    • Acute impairment of learning, memory, and attention
    • Increased incidence of suicide ideation, attempts, and completions
    • Development of substance abuse for tobacco, alcohol, and illicit drugs
  • Limited evidence for:
    • Triggering heart attack
    • Pregnancy complications (for maternal cannabis smokers)
    • Impaired academic achievement and education
    • Increased unemployment and lower income
    • Development of anxiety disorder
  • Insufficient/insubstantial evidence for:
    • Incidence of esophageal, prostate, cervical, anal, bladder, and other types of cancer (see full report for list)
    • Asthma development or exacerbation
    • Death due to cannabis overdose
    • Occupational accidents
    • Development of PTSD

 

  1. Lynch ME, Campbell F. Cannabinoids for treatment of chronic non-cancer pain; a systematic review of randomized trials. British Journal of Clinical Pharmacology72: 735–744, 2011. http://www.nationalacademies.org/hmd/Reports/2017/health-effects-of-cannabis-and-cannabinoids.aspx
  2. The health effects of cannabis and cannabinoids: the current state of evidence and recommendations for research. Washington, DC: The National Academies Press, 2017. http://www.nationalacademies.org/hmd/Reports/2017/health-effects-of-cannabis-and-cannabinoids.aspx
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