Medical Marijuana: Current Scientific Basis 2018 – Part II

Medical Marijuana: Current Scientific Basis 2018 – Part II

This is Part II of a two-part series on medical marijuana. In Part I last week, we surveyed just what the term medical marijuana means. We also looked at why there is a gap between scientific research results and physiological effects of products actually sold as medical marijuana. This week, we will look at the results of actual scientific studies into the drug and health effects of marijuana.

I’m not pulling any punches today. I will warn you now that this is probably the driest post I have written to date. I make no apologies for providing a lot of densely-packed factual information.

As discussed in detail last week, medical marijuana includes both the cannabis plant and cannabinoids. Cannabinoids include anything extracted from the plant. If you do not recognize any of the medical marijuana products discussed below, please refer back to Part I, which includes a comprehensive list of cannabinoids.

By law, researchers in the United States are restricted to using cannabis and cannabinoids controlled by the National Institute of Drug Abuse (NIDA). The NIDA marijuana is based the cannabis plants commonly grown in the twentieth century. It is not as potent as the modern strains currently sold through medical marijuana dispensaries.


 The lists that follow may be a bit dry to read. The upside is that these are real research results. I have culled these from solid scientific sources like PubMed, the National Academy of Science, the government’s database of clinical studies and other high-level databases and journals.

What you will read below represents the state of the art of medical marijuana research in the United States as of the beginning of 2018.

  • CHRONIC PAIN. There is strong evidence based on quality scientific studies that cannabis is an effective treatment for chronic pain in adults.
    • By law, these studies used cannabis and cannabinoid drugs approved and controlled by the U.S. National Institute of Drug Abuse (NIDA).
    • None of the studies used the cannabis-plant products currently sold in most medical marijuana dispensaries. For this reason, claims are weak that cannabis-plant products sold in state-legal dispensaries are safe and effective for pain.
  • CHEMOTHERAPY SYMPTOMS. There is strong evidence that oral cannabinoids are effective antiemetics in the treatment of chemotherapy-induced nausea and vomiting.
    • There is an abundance of anecdotal reports on the benefits of marijuana as an remedy for chemotherapy-induced nausea and vomiting. Unfortunately, there are no unbiased clinical trials investigating plant marijuana for chemotherapy side effects. Nor have any of the unbiased studies investigated cannabidiol or cannabidiol-enriched cannabis for chemotherapy-induced nausea and vomiting.
  • MULTIPLE SCLEROSIS SPASTICITY. There is substantial evidence that oral cannabinoids are effective for improving patient-reported multiple sclerosis spasticity symptoms.  There is limited evidence for a positive effect on clinician-measured spasticity.
    • The cannabinoids studied include nabiximols, dronabinol, and oral THC/CBD, and oral cannabis extract.
    • There were no studies which researched vaporized. inhaled or ingested cannabis-plant products.
  • SLEEP DISTURBANCE. There is moderate evidence that cannabinoids, primarily nabiximols, are effective in improving short-term sleep for people with obstructive sleep apnea syndrome, fibromyalgia, chronic pain, and multiple sclerosis.
    • The studies in question used THC/CBD capsules, nabiximols, and  dronabinol.


The following fall into the “limited evidence” classification as defined by the National Academy of Science. This means that the number of studies on an particular drug effect were small.

  • AIDS WASTING SYNDROME. There is limited evidence that cannabis and oral cannabinoids are effective in increasing appetite and decreasing weight loss associated with HIV/AIDS.
    • There have been no good-quality studies recently on cannabis or cannabinoids for AIDS wasting syndrome. This is mostly due to the virtual disappearance of this syndrome since effective anti-retroviral therapies became available in the mid-1990s for AIDS/HIV.
  • TOURETTE SYNDROME. There is limited evidence that THC capsules are effective for improving the symptoms of Tourette syndrome.
    • There is no clear link between the symptoms of Tourette syndrome and the cannabinoid neuroreceptor sites in the nervous system. Regardless, case reports suggest that cannabis does reduce Tourette tics.
    • The therapeutic effects of cannabis might be due to the anxiety-reducing properties of marijuana rather than to a specific anti-tic effect.
  • ANXIETY. There is limited evidence that cannabidiol is an effective for the improvement of anxiety symptoms based on a public speaking test using individuals with social anxiety disorders.
    • These positive findings are limited by weaknesses in the design of the study.
    • In contrast, evidence from observational studies found that daily cannabis use is associated with increased anxiety symptoms.
    •  Heavy cannabis use is associated with social phobia disorder.
  • POST-TRAUMATIC STRESS DISORDER. There is limited evidence (a single, small fair-quality trial) that nabilone is effective for improving symptoms of posttraumatic stress disorder.
    • A handfull of studies going on right now that will add to this data


Most of these studies fall into the “limited evidence” classification as defined by the National Academy of Science. This means that the number of studies on an particular drug effects were small. The results will mention only the products that were used in a study. Medical marijuana products that were not studied are not mentioned.

In most cases, there were not further studies because of the difficulty of doing marijuana research in the United States. When a small number of studies show a negative effect, funding typically dries up. Federal agencies do not invest in research projected to produce more negative results.

  • GLAUCOMA. There is limited evidence that cannabinoids are an ineffective treatment for improving the  intraocular pressure associated with glaucoma.
  • DEMENTIA. There is limited evidence that oral cannabinoids are ineffective treatments for improving the symptoms associated with dementia.
  • DEPRESSION. There is limited evidence that nabiximols, dronabinol, and nabilone are ineffective treatments for the reduction of depressive symptoms in individuals with chronic pain or multiple sclerosis.


In these cases, the studies available reported either positive and ineffective results in near-equal amounts. Studies with ambivalent results also fall into this category.

  • There is not enough evidence to confirm or refute the effect of cannabis or cannabinoid drugs on cancer.
  • There is insufficient evidence to support or refute that cannabinoids are effective for cancer-associated anorexia-cachexia syndrome and anorexia nervosa.
  • There is insufficient evidence to support or refute that dronabinol is effective for the symptoms of irritable bowel syndrome.
  • There is insufficient evidence to support or refute that cannabinoids are effective for epilepsy in general.
  • There is insufficient evidence to support or refute that cannabinoids are effective for spasticity with paralysis due to spinal cord injury.
  • There is insufficient evidence to support or refute that oral cannabinoids are effective for chorea and certain neuropsychiatric symptoms associated with Huntington’s disease.
  • There is insufficient evidence that cannabinoids are effective for the motor system symptoms associated with Parkinson’s disease or the levodopainduced dyskinesia.
  • There is insufficient evidence to support or refute that nabilone and dronabinol are an
    effective treatment for dystonia. Cannabis was not studied.
  • There is no evidence to support or refute the conclusion that cannabinoids are an effective treatment for
    achieving abstinence from addictive substances.
  • There is insufficient evidence to support or refute the conclusion that cannabidiol is an effective treatment for the mental health outcomes in individuals with schizophrenia or schizophreniform psychosis.
  • Some preliminary studies have suggested that medical marijuana legalization might be associated with decreased prescription opoid use and overdose deaths, but researchers don’t have enough evidence yet to confirm this finding.
    • For example, one NIDA-funded study suggested a link between medical marijuana legalization and fewer overdose deaths from prescription opioids. But this study didn’t show that medical marijuana legalization caused the decrease in deaths or that pain patients changed their drug-taking behavior.
    • A more detailed NIDA-funded analysis showed that legally protected medical marijuana dispensaries, not just medical marijuana laws, were also associated with a decrease in the following:
      • opioid prescribing,
      • self-reports of opioid misuse,
      • treatment admissions for opioid addiction.


If someone’s favorite illness or disorder isn’t listed above, that means there really isn’t any decent science that passed peer-review level scrutiny. Non-random studies and biased studies have been excluded. Most of the above research results listed here were culled from the 2017 report on medical marijuana published by the National Research Council.

If you are overwhelmed by how little we know from a hard-science perspective, you are not alone. Most of what people think they know about medical marijuana is based on anecdotal hearsay. The peer-review bar for science is high – and it has to be when you’re dealing with issues of public health!

It is important to keep in mind that the medical marijuana movement was not pushed by the scientific or medical establishments. It is a grassroots phenomenon that is political in nature. Science and medicine can’t push or impede medical marijuana for the most part because of the substantial barriers to research. As a results, the disconnect between the claims for medical marijuana and what research results actually show is profound.


The problems with medical marijuana research are many.

  • The biggest hurdle is the classification of cannabis and cannabinoids as Schedule I substances, as discussed last week in Part I. It is very difficult to research the medicinal benefits of a substance which has been defined as having none by law. This is the phenomenon of contempt prior to investigation.
  • The federal government’s regulatory process for doing any cannabis-related research is an impediment all by itself.
  • Forcing researchers to use a dated-cannabis strain that is impotent by today’s standards calls into question the validity of many study results.

I have not gone into the adverse effects of cannabis and cannabinoids. There are some and they are scary, especially for children and adolescents. This two-part series is focused on what we actually know about the benefits or detractions of medical marijuana – and nothing else. The physiology of marijuana as a recreational drug is a different topic for a different day.

The National Academies of Science and Health have called for a reformation in how the federal government regulates research into medical marijuana – and they are right to do so. Without more and better research into what the medical marijuana dispensaries are actually selling people, the debate on the potential benefits of cannabis-based drugs will remain mired in hearsay and politics.

Today’s sources of information are the same as the ones cited last week in Part I.

Today’s banner image is from the U.S. National Institute on Drug Abuse and is in the public domain.

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