This literature review was conducted using Google Scholar, which was used to find citations of academic papers that referenced “cannabis medicine”, “cannabis psychosis”, “cannabis schizophrenia” and “medicinal cannabis”.
The strands of research that interest us here include: research undermining cannabis prohibition, with reference to psychiatric concerns; research supporting use of cannabis medicine, with reference to psychiatric conditions; evidence for cannabis as a substitute for opioids; other evidence supporting the use of cannabis medicine.
Research undermining cannabis prohibition, with reference to psychiatric concerns
This paper in the Biological Psychiatry Journal was notable for containing the sentence “Meta-analyses suggest that individuals with schizophrenia who use cannabis show better cognitive functioning compared to those who are non-users.”
Another paper in the Schizophrenia Bulletin makes a point of distinguishing between the effects of CBD and the effects of THC, noting that “THC is responsible for the psychotogenic effects of cannabis.” This directly contradicts the received psychiatric wisdom that “cannabis” causes psychosis.
This paper even notes that “independent evidence that CBD has antipsychotic and anxiolytic properties in patients with mental health disorders has been accumulating.” Indeed, doctors in California have been advising people for at least 10 years now that high-CBD strains (such as Northern Lights) were better suited for calming and sleeping purposes than high-THC skunk.
Although this paper is not titled with a journal of publication, it is worthwhile for at least conceding that many of the negative symptoms of schizophrenia are ameliorated by cannabis use.
This paper in the Acta Psychopathologica argues against the prohibition of cannabis on the basis of the Precautionary Principle. According to this paper, almost everyone tempted to smoke cannabis already has, regardless of the law. Moreover, prohibition prevents very few cases of schizophrenia, even assuming a direct causal link. Therefore, the deterrent effect of prohibition is outweighed by the positive effects of making it legal.
Research supporting use of cannabis medicine, with reference to psychiatric conditions
This paper in the the Clinical Psychology Review performed a meta-analysis of recent discoveries about the relationship between medicinal cannabis use and positive mental health outcomes. Perhaps the foremost result of this analysis was “Cannabis has potential for the treatment of PTSD and substance use disorders.” Among cannabis users this is well-known to be one of the main reasons why people smoke it in the first place. It was also noted that “Cannabis use does not appear to increase risk of harm to self or others.”
What is striking about this paper is the absence of Drug War rhetoric. Cannabis use, instead of being described as cannabis abuse (as in the majority of prohibitionist papers), is here given the acronym CTP (cannabis for therapeutic purposes). In the past, a paper that referred to cannabis in this manner would not have been funded or published, so the appearance of the phrase suggests that attitudes are changing.
A comprehensive overview of recent advances in medicinal cannabis science can be found in the Handbook of Cannabis and Related Pathologies Chapters 90 and 91, ‘The Use of Medical Marijuana in the Treatment of Psychiatric Disorders’ and ‘Beneficial Effects of Cannabis and Related Compounds on Sleep’.
Unfortunately, much of the literature continues to make the fundamental error of confusing cannabis extracts and pharamceutical preparations with the actual cannabis plant itself (as seen here). The authors of these papers frequently draw the conclusion that cannabis is not helpful for treating certain conditions because some extract was found to not be helpful. Others (as seen here) fail to make any distinction between THC and CBD, lumping all 100+ cannabinoids under the rubric of “marijuana”.
This paper notes that anxiety is one of the top five reasons given by patients in North America for using medicinal cannabis. It doesn’t go into why, but it’s likely that the calming effects of CBD are involved, as they may also be in the case of schizophrenia. Other papers also support the notion that cannabis has use for treating certain mental conditions, such as social anxiety.
Evidence for cannabis as a substitute for opioids
One of the most promising directions of future medicinal cannabis research appears to be in the direction of using cannabis as a substitute for a variety of other medicines that might have worse side-effects or addictive potential.
One of the most astonishing pieces of research was a study of how usage of pain, anxiety and sleep medication decreased when medicinal cannabis was available. In a survey of New England dispensary members, “among respondents that regularly used opioids, over three-quarters (76.7%) indicated that they reduced their use since they started [medicinal cannabis]…” and “…Approximately two-thirds of patients decreased their use of anti-anxiety (71.8%), migraine (66.7%), and sleep (65.2%) medications following [medicinal cannabis]…”.
Another example can be found here. The linked study is a literature review of 2897 medicinal cannabis patients that found “Respondents overwhelmingly reported that cannabis provided relief on par with their other medications, but without the unwanted side effects.”
In particular there seems to be special promise for cannabis to help with the opioid addiction crisis. Several papers suggest promise for cannabis to help here, as well as act as a substitute for sleep medications.
Other evidence supporting the use of cannabis medicine
Soporific uses appear to be one of the most promising avenues for future research into the benefits of medicinal cannabis. This study found reason to support the idea that cannabis heavy in CBDs is better suited for sleep management than cannabis heavy in THCs.
This review in Clinical Psychopharmacology and Medicine suggested that there might be promise in using cannabis to treat Alzheimers’s, Huntington’s and Parkinson’s diseases, among other neurodegenerative conditions.
This study suggested that the savings from prescriptions that don’t get filled in legal cannabis states (because legal medicinal cannabis acts as a substitute for the prescribed medicine) could run into the billions.
What many of these studies have in common is a mention of the need for more research into the potential for cannabis to alleviate suffering, and a lament for the fact that this research has been hamstrung by cannabis prohibition. It’s clear that awareness of the benefits of cannabis medicine is spreading rapidly among the medical community, and that there is much excitement about future applications.
Vince McLeod is a former Membership Secretary of the Aotearoa Legalise Cannabis Party and author of the Cannabis Activist’s Handbook.