Issues in Interdisciplinarity 2020-21/Evidence in the Medicinal usage of Cannabis

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Introduction[edit | edit source]

The use of herbal substances to relieve pain and treat disorders is an ancient medicinal method.[1] In modern society, this idea has been extended to include debate surrounding the medicinal use of illegal substances like cannabis. There has been much controversy on a disciplinary level due to the different research methods employed in approaching this issue, and subsequently, the different modes of evidence procured. This has resulted in tension between academic disciplines.[2] How could these approaches be mediated? And can they result in a beneficial interdisciplinary perspective which may provide a broader and more informed scope regarding Medical Cannabis?

Evidence in Psychology[edit | edit source]

Psychology uses qualitative research methods- including open-ended questionnaires/interviews- and quantitative- clinically-focused reviews and more statistical, positivist surveying methods, for example- to acquire evidence.[3] These are equally as fruitful in observation of the topic in question.

Regarding systematic reviews, one clinically-focused review was undertaken in 2020, with researchers observing plant formulations, clinical prescriptions of subjects, and their occupational and health elements. Although overall findings of each study were described as ‘nascent’ in relation to each other, isolated studies suggested advocacy for the use of CBD for sufferers of anxiety and schizophrenia.[4] This mode of research presents some benefits: it provides a holistic glance into the efficacy of cannabis on treating mental health issues, with acknowledgement of variables in subjects’ health conditions and occupations. However, there are shortcomings within this. One could argue that the positivist nature of the findings ignores the nuances of the human condition as it does not incorporate direct testimonies of those afflicted with mental health issues.[5]

Furthermore, evidence can be gleaned through the utilisation of qualitative methods including online forums. A forum was hosted by AZDHS[6] in 2013 about the use of cannabis to treat PTSD, with comments being indexed online. General observations found that there was overwhelming advocacy of this from sufferers of the disorder, with claims that it lessens “the brain's sensitivity to outside triggers that can exacerbate PTSD symptoms”.[6] While this mode of evidence provides a more contextualised, humane exploration of this topic, it is limited in the sense that logically, the forum would be dominated by those who are advocates of the cause as opposed to detractors, opening up the possibility of bias within the responses gleaned and consequently narrows the validity of the evidence.[5]

Evidence in Pharmacology[edit | edit source]

One of the early pharmaceutical randomised controlled trials regarding cannabis in relation to anorexia nervosa was published in 1983. One method used was a qualitative questionnaire answered by the participants. The results showed that the subjects who received the active substances in cannabis, Δ9-Tetrahydrocannabinol or THC, improved sleep and experienced less anxiety than those who received placebo. This information was however later presented in quantitative form through tables and diagrams.[7] The trial also conducted quantitative research by measuring weight of the participants but the used dose of THC did not provide a significant effect.[7]

Additionally, a randomised controlled trial in 2017 showed quantitative evidence that THC in form of Dronabinol© can be used to treat Anorexia Nervosa by showing a larger increase in weight of patients who received THC in comparison to those who received placebo. An aspect of the study was that patients with depression or other psychiatric disorders were excluded from the trial[8] This made the study more focused on the weight gain and thus the quantitative evidence available.

In opposition to the two trials previously discussed, a study from Oxford University in 2008 aimed to examine the side effects of medical cannabis. The study provided preliminary evidence from Magnetic Resonance Imaging that long term use of cannabis damages Corpus Callosum. The MRI scan was analysed by separating it into voxels, calculating the eigenvalues and eigenvectors and lastly the values were normalised. The images were also qualitatively analysed and visually compared to placebo.[9] These methods show that the MRI scan provided both qualitative and quantitative evidence.[9][10]

Furthermore, physiological side effects connected to failure in the digestive and cardiovascular systems reoccur in control trials.[11] Several studies on both model organisms and humans provide empirical evidence that the side effects depend on the relation between THC and the endocannabinoid system in the brain.[12][13]

Evidence in Law[edit | edit source]

In contrast to analysing the issue of medical cannabis from the psychological and pharmacological aspects, a legal perspective provides contradictory evidence.

In the United Kingdom, questions about the medical use of cannabis has been regarded since 1998. The House of Lords had selected the Science and Technology Committee to investigate on the possibility of using cannabis for medical reasons. They concluded that there was enough convincing evidence that cannabis had medical capacities to treat many forms of pain. They also recommended starting trials of cannabis to treat medical problems. However, the UK government did not accept the committee’s recommendation.[14] This was partially changed in November 2018 as the government changed the law after the Home Secretary acknowledged raised concerns of parents of children with illnesses such as epilepsy. The current law allows specialist doctors to take the decision to prescribe unlicensed medicines in form of cannabis. However, the law makes it clear that the use of cannabis for recreational purposes is still illegal and that penalties concerning unauthorised use will remain as it was.[15]

In April 2019, Emma Appleby, mother of a nine-year-old girl with severe epilepsy and a rare chromosomal disorder, saw her £4.500 of cannabis oil confiscated by officials after entering the UK from a trip to Holland. Appleby was devastated to not be allowed to use the cannabis oil on her daughter as it was the only solution she found to relieve her daughter’s pain. She also stated that she tried several pharmaceutical “drugs and diets", but all failed to remove her daughter’s pain and symptoms. Appleby added that some treatments made the case worse as they caused side effects.[16] As mentioned, the law was changed in November 2018, however it seems like parents have struggled to get prescriptions.[15][16]

Conclusion[edit | edit source]

Through integrating elements of a psychological approach with phamacological evidence, academics can acquire a holistic understanding of the issue of medical cannabis. Not only by observing evidence within the two separate disciplines to gain understanding regarding the psychological and physiological effects of medical cannabis, but also through the utilisation of both quantitative and qualitative research methods in both disciplines. As demonstrated, these research methods garner evidence of both a positivist and interpretive nature, mediating both for a deeper enquiry in determining medical cannabis’ capacity to treat mental health issues. These methods account for external factors that may have implications on this topic, and that may otherwise be difficult to observe empirically. Moreover, from a legal perspective, this evidence can be put into practice through updating of the regulations in place, which makes prescription of the drug contingent on a doctor's opinion, making it very difficult to access for some people. An interdisciplinary approach would be beneficial in developing those regulations, through the incorporation of evidence from psychology, pharmacology and law to craft a path towards more modernised and evidence-based forms of medication.

References[edit | edit source]

  1. Petrovska BB. Historical review of medicinal plants’ usage. Pharmacognosy Review [Internet]. 2012 Jan [cited 2020 Dec 7];6(11):1-5. Available from: DOI: 10.4103/0973-7847.95849
  2. Joy J, Mack A. Marijuana as Medicine?: The Science Beyond the Controversy. National Academies Press [Internet]. 2000 [cited 2020 Dec 8];10(1):article 3. Available from: DOI: 10.17226/9586
  3. de Beer LT, de Klerk W, Scholtz SE. The Use of Research Methods in Psychological Research: A Systematised Review. Frontiers in Research Metrics and Analytics [Internet]. 2020 Mar [cited 2020 Dec 11];5(1):article 1. Available from: DOI:
  4. Davidson M, Firth J, Karamacoska D, Sarris J, Sinclair J. Medicinal cannabis for psychiatric disorders: a clinically focused systematic review. BMC Psychiatry [Internet]. 2020 Jan 16 [cited 2020 Dec 11];20(1):article 24. Available from: DOI: 10.1186/s12888-019-2409-8
  5. a b Mays N, Popay J, Pope C. Systematically reviewing qualitative and quantitative evidence to inform management and policy-making in the health field. London School of Hygiene and Tropical Medicine [Internet]. 2005 Jul 1 [cited 2020 Dec 14];10(1):3-4(6-20). Available from: DOI:
  6. a b Arizona Department of Health Services [Internet]. Arizona: ADHS; 2013 Jun. Public Comments Received about PTSD on the ADHS Website; 2013 Oct[cited: 2020 Dec 10]; [2 screens]. Available from:
  7. a b Caine E, Ebert M, Faden V, Goldberg S, Gross H, Hawks R, Kaye W, Zinberg N. A Double-Blind Trial of Δ9-Tetrahydrocannabinol in Primary Anorexia Nervosa. Journal of Clinical Psychopharmacology. 1983 Jun;3(3):165-171.
  8. Andries A, Frystuk J, Flyvbjerg A, Klinkby E. Dronabinol in severe, enduring anorexia nervosa: A randomized controlled trial. International Journal of Eating Disorders [Internet]. 2013 Sep 14 [cited 2020 Dec 12];47(1):13-23. Available from: DOI:
  9. a b Arnone D, Barrick TR, Chengappa S, Mackay CE, Clark CA, Abou-Saleh MT. Corpus callosum damage in heavy marijuana use: Preliminary evidence from diffusion tensor tractography and tract-based spatial statistics. NeuroImage [Internet]. 2008 Jul 1 [cited 2020 Dec 3];41(3):1067-1074. Available from: DOI:
  10. Pierpaoli C. Quantitative Brain MRI. HHS Public Access [Internet]. 2010 Apr [cited 2020 Dec 3];21(2):63. Available from: DOI: 10.1097/RMR.0b013e31821e56f8
  11. Shenglong Z, Ujendra K. Cannabinoid Receptors and the Endocannabinoid System: Signaling and Function in the Central Nervous System. International Journal of Molecular Sciences [Internet]. 2018 Mar [cited 2020 Nov 28];19(3):833. Available from: DOI: 10.3390/ijms19030833
  12. Bonz A, Laser M, Küllmer S, Kniesch S, Babin-Ebell J, Popp V, et al. Cannabinoids Acting on CB1 Receptors Decrease Contractile Performance in Human Atrial Muscle. Journal of Cardiovascular Pharmacology. 2003 Apr;41(4):657–64. Available from: ‌
  13. Wagner JA, Abesser M, Karcher J, Laser M, Kunos G. Coronary Vasodilator Effects of Endogenous Cannabinoids in Vasopressin-Preconstricted Unpaced Rat Isolated Hearts. Journal of Cardiovascular Pharmacology. 2005 Sep;46(3):348–55. Available from: ‌
  14. Degenhardt L, Hall W. Medical Marijuana Initiatives. CNS Drugs [Internet]. 2012 Aug 29 [cited 2020 Dec 12];17(1):689-697. Available from: DOI:
  15. a b GOV.UK [Internet]. United Kingdom: Home Office: Sajid Javid; 2018. Government announces that medicinal cannabis is legal; 2018 Oct 11 [cited 2020 Dec 12]; [2 screens]. Available from:
  16. a b The Guardian [Internet]. United Kingdom: Mattha Busby; 2019. Mother of girl with epilepsy has supply of medical cannabis confiscated; 2019 Apr 6 [cited 2020 Dec 11]; [3 screens]. Available from: