IMR Review: Medical Hemp Claims Still Not Proven

IMR researchers find limited clinical evidence for hemp to treat multiple sclerosis, epilepsy, chronic pain, cancer, inflammation, or constipation, or to promote sleep, and skin and brain health.

KUALA LUMPUR, June 15 – Local researchers from the Institute for Medical Research (IMR) found a lack of clinical evidence for hemp in treating the symptoms of multiple conditions, including chronic pain, cancer, and epilepsy. 

IMR’s peer-reviewed systematic review published January 2021 in the Plos One journal looked at the current evidence for the health effects of hemp on multiple sclerosis, epilepsy, anxiolytic effects to improve sleep, skin and brain health, anti-inflammatory effects, chronic pain, cancer, and constipation.

“Despite popular claims of health benefits of hemp on various websites from a basic google search performed using the search phrase ‘health benefits of hemp’, we found no strong evidence to support the use of hemp for any specific indication,” said the research team consisting of doctors, pharmacists and biomedical researchers who conducted literature searches between January 2009 and December 2019.

“Current evidence on hemp-specific interventions are still preliminary, with limited high quality clinical evidence for any specific therapeutic indication.

“This is mainly due to the wide variation in test item formulation, as the multiple variants of this plant differ in their phytochemical and bioactive compounds. Future empirical research should focus on standardising the hemp plant for pharmaceutical use, and uniformity in experimental designs to strengthen the premise of using hemp in medicine.”

Hemp comes from the same Cannabis sativa plant species as marijuana, but has lower levels of the psychoactive compound, THC, that is legally capped in the United States at less than 0.3 per cent and in the European Union at 0.2 per cent. Hemp contains more cannabidiol (CBD) that does not produce psychoactive effects.

On multiple sclerosis, a disabling autoimmune disease, IMR’s review found that although marijuana-based oromucosal spray (Sativex) is in use as an add-on treatment for spasticity among multiple sclerosis patients, the mechanism of action of Sativex is unclear.

“Although both marijuana and hemp belong to the same plant species C. sativa, no clinical papers were identified to support hemp’s therapeutic use in multiple sclerosis.”

IMR’s review also highlighted insufficient evidence for the efficacy of Epidiolex that contains CBD, although the marijuana-based oral solution has been approved for treatment of rare and severe forms of epilepsy, including Lennox-Gastaut syndrome and Dravet syndrome.

“Due to study design limitations of small sample size, inclusion of various types of epilepsies, lack of control or comparator group, lack of randomisation and blinding, self-reported retrospective study design, and a lack of statistical power for results interpretation in these studies, it is not possible to draw strong conclusions from our findings,” researchers said.

“It is also clear that more studies are needed before claims of hemp’s benefits in refractory epilepsies could be made.”

IMR’s review noted the limited number of high quality human trials to prove the efficacy of hemp in relieving chronic pain, despite some evidence on the efficacy of marijuana to deal with chronic neuropathic pain that has failed other conventional therapies. 

Although there is some pre-clinical data that demonstrated the anti-cancer potential of hemp, IMR researchers found no strong evidence to support the use of hemp in any type of cancer, as the data is still preliminary.

“With the current understanding that hemp of different cultivars contain a variety of compounds yet to be fully identified with various concentrations, further studies are needed.”

IMR researchers found no strong clinical evidence for claims on the role of hempseed in promoting sleep and reducing anxiety, although they acknowledged a study on how a single-dose oral CBD promoted anxiolytic effects among 60 healthy volunteers.

However, researchers noted that the study and its results were not reliable as there was no sample size calculation and the duration of the research was short. 

“To the best of our knowledge, there have been no studies in humans or animals that report hempseed’s benefits in improving sleep or as an anxiolytic,” IMR said.

“Given that hempseed oil of different sources and cultivar contain a variety of cannabinoids including CBD at different quantities, it is therefore not suitable to directly imply that hemp exhibits beneficial anxiolytic effects as reported for CBD.”

At the same time, IMR’s review pointed out that commercially purchased hemp-based ointment that claimed to promote skin health was not reliable due to its unclear formulation content.

Although the potential of hemp has been identified in some cell studies for acne, researchers advised for further investigation on the formulation and doses needed for different severities of acne to prove the effectiveness of hempseed as an anti-acne agent in humans.

Furthermore, IMR’s review highlighted deficiency in pre-clinical evidence on the efficacy of hemp for conditions related to the central nervous system, such as neuroinflammation, Alzheimer’s disease, eye degeneration and traumatic brain injury. 

“With limited therapeutic options and high failure rates of clinical trials for such neurological disorders, more robust preclinical studies are needed to materialise translation into successful clinical trials.”

IMR’s review found varying anti-inflammatory effects across studies on hemp, noting that the mechanism behind these different effects was unclear. 

“The use of different formulations and test items further made direct comparison between studies difficult. More studies are required to translate such data into clinically significant models.”

On constipation, IMR’s review found just one strong trial on Chinese medicine pill MaZiRenWan, which contains hempseed and other herbs, that focused mainly on Chinese female patients.

“Further investigation needs to be conducted to detail the mechanism of hemp contributing to such synergism,” said researchers.

Several electronic databases including MEDLINE, OVID (OVFT, APC Journal Club, EBM Reviews), Cochrane Library Central and were used to conduct literature searches for IMR’s study. 

Keywords like “Medicinal OR Therapeutic OR Benefit OR Effect OR Properties OR Bioactive” and “Hemp OR Hemps OR Cannabidiol” were used for the literature searches across different databases.

A total of 65 articles were included in IMR’s survey out of 11,305 records that were initially identified based on the keyword search. 

“The relatively small number of articles included compared to the results on initial research suggests that hemp research only makes up a small proportion of the total pool of cannabis-related research, similar to marketed cannabis-based drug trends which are either derived from marijuana or synthetically produced,” IMR researchers said.

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