Cannabis use by individuals with multiple sclerosis: effects on specific immune parameters

Medical Cannabis Use and Inflammatory Cytokines and Chemokines Among Adult Chronic Pain Patients

Background: Utilizing cannabis as a therapeutic option for chronic pain (CP) has increased significantly. However, data regarding the potential immunomodulatory effects of cannabis in CP patients remain scarce. We aimed at exploring the relationship between cannabis use and inflammatory cytokines and chemokines among a cohort of CP patients. Methods: Adult patients with a CP diagnosis and medical authorization of cannabis were enrolled. Patients completed validated clinical questionnaires and self-reported the effectiveness of cannabis for symptom management. Patients' blood and cannabis samples were analyzed for the presence of four major cannabinoids, two major cannabinoid metabolites, 29 different cytokines/chemokines, and cortisol. The multivariable linear regression model was used to identify cannabis and patient factors associated with immune markers. Results: Fifty-six patients (48±15 years; 64% females) were included, with dried cannabis (53%) being the most common type of cannabis consumed. Seventy percent of products were considered delta-9-tetrahydrocannabinol (Δ9-THC)-dominant. The majority of patients (96%) self-reported effective pain management, and 76% reported a significant decrease in analgesic medication usage (p≤0.001). Compared with males, female patients had higher plasma levels of cannabidiol (CBD), cannabidiolic acid, Δ9-THC, and 11-hydroxy-Δ9-tetrahydrocannabinol but lower concentrations of delta-9-tetrahydrocannabinolic acid and 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH). Females had significantly lower eotaxin levels (p=0.04) in comparison to male patients. The regression analysis indicated that high cannabis doses were related to increased levels of interleukin (IL)-12p40 (p=0.02) and IL-6 (p=0.01), whereas female sex was associated with decreased eotaxin (p≤0.01) concentrations. Blood CBD levels were associated with lower vascular endothelial growth factor (p=0.04) concentrations, and THC-COOH was a factor related to decreased tumor necrosis factor alpha (p=0.02) and IL-12p70 (p=0.03). Conclusion: This study provides further support for the patient-perceived effectiveness of cannabis in managing CP symptoms and reducing analgesic medication consumption. The results suggest a potential sex difference in metabolizing cannabinoids, and the varying immune marker concentrations may support a possible immunomodulatory effect associated with patient sex and cannabis product type. These preliminary findings provide grounds for further validation using larger, well-designed studies with longer follow-up periods.

Inhibition of FAAH suppresses RANKL-induced osteoclastogenesis and attenuates ovariectomy-induced bone loss partially through repressing the IL17 pathway

Fatty amide hydrolase (FAAH) is a key degradation enzyme of the endocannabinoid system, mainly responsible for the hydrolysis of arachidonic acid ethanolamine (AEA). Previous investigations have shown that FAAH is involved in a series of biological processes, such as inflammation, immune regulation, and transmembrane signal transduction of neurons. Endogenous cannabinoids and cannabinoid receptors have been reported to participate in the regulation of bone homeostasis by regulating the differentiation of osteoblasts and osteoclasts. We hypothesized that FAAH may play an important role in osteoclastogenesis based on the above evidence. The present study found that the FAAH expression was increased at both mRNA and protein levels during RANKL-induced osteoclastogenesis. Pharmacological and genetic inhibition of FAAH in bone marrow-derived macrophages (BMMs) inhibited osteoclastogenesis, F-actin ring formation, bone resorption, and osteoclast-specific gene expression in vitro. Moreover, intragastric administration of the FAAH inhibitor PF-04457845(PF) ameliorated ovariectomy (OVX)-induced bone loss in mice. Further investigation revealed that nuclear factor κB (NF-κB) and mitogen-activated protein kinase (MAPK) pathways were inhibited by PF treatment and FAAH knockdown. RNAseq indicated that the IL17 pathway was blocked by PF, and administration of recombinant murine IL17 protein could partially restore osteoclastogenesis and activate NF-κB and MAPK pathways. To sum up, our findings demonstrate that targeting FAAH could be a promising candidate strategy for treating osteoclast-related diseases, especially osteoporosis.

Is interleukin-17 implicated in early knee osteoarthritis pathogenesis as in rheumatoid arthritis?

Background

Interleukin-17 (IL-17) is a cytokine that promotes activation of multiple catabolic pathways resulting in cartilage and tissue damage. It has features making it increasingly attractive as a biological marker, especially in rheumatoid arthritis (RA) and osteoarthritis (OA). However, its expression is heterogeneous; not all patients’ exhibit high IL-17 levels, and its level along the disease course is still challenging to predict.

Aim of the work

The objectives of this study were to compare serum IL-17 levels in patients with early knee OA and in RA patients, to determine its correlation with disease activity in RA and to determine if it is correlated with functional scores in both RA and OA.

Subjects and methods

Twenty early knee OA patients (32.7 ± 3.7) years were included. Diagnosis of early OA was based on Luyten et al. 2012 early knee OA classification (early OA 2012). This study also included 25 RA patients aged 32.8 ± 5.1 years, and the diagnosis was according to 2010 ACR-EULAR classification criteria for RA. The current work also included a control group of 20 healthy volunteers aged 31.9 ± 3.2 years. The serum IL-17 level was assessed by using the ELISA technique.

Results

Serum IL-17 level was significantly high in early knee OA patients (5.2 pg/ml) and was significantly higher in RA patients (5.9 pg/ml) compared to the control group (4.9 pg/ml) (P < 0.001).

Conclusions

The increased serum IL-17 level in patients with early knee OA suggests its pathogenic role in the disease. Serum IL-17 positive correlation with the severity of knee OA-related pain proposes that it may be a potential marker to target for early treatment of knee OA-related pain.

Implications of Cannabis and Cannabinoid Use in COVID-19: Scoping Review

ABSTRACT Objective: to identify and synthesize studies on the effects of cannabis use and its relation with SARS-CoV-2, as well as the therapeutic possibilities of using cannabinoids in the prevention and treatment of COVID-19. Methods: scoping review, in the BVS, PubMed, SCIELO, CINAHL, SCOPUS, Web of Science, MedNar, CAPES and ProQuest databases, with no language restriction and year limitation. Narrative synthesis was performed. Results: cannabis use causes changes in the respiratory and vascular system, it reduces the production of cytokines, which affects the users’ immune system, increasing the susceptibility to infection and progression of COVID-19. However, studies have suggested the use of cannabinoids in the prophylaxis and treatment of COVID-19, due to their anti-inflammatory effect. Conclusions: the use of inhaled cannabis increases the progression and severity of the infection. On the other hand, the benefits of cannabinoids seem promising to modulate the immune system, but it needs further studies.

Living with the virus: Infection and epidemiology of COVID-19 in hotspot area of India

The coronavirus disease (COVID-19) has been identified as a pandemic and affected almost whole world. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of this disease, is infecting Indian population since the last week of January 2020. The data were collected from January 30, 2020, to May 23, 2020, to analyze basic trend of COVID-19 cases in India targeting hotspot regions. To find the linear relationship between variables, that is, age, total positive cases, population, and population density data have been statistically analyzed. COVID-19 caused more than 5000 deaths till May 2020 in India. SARS-CoV-2 spread to several Indian cities with more than 100,000 positive cases. Total number of COVID-19 cases and total recovered cases followed the exponential distribution, while number of deaths showed linear behavior. Nearly 50% of the youth, that is, 20-40 years of age had been found to recover from the infection. As a lockdown cannot be a permanent solution, it is important to understand the nature of virus and learn "living with the virus" while minimizing its spreading at the same time.

Cannabinoids and bladder symptoms in multiple sclerosis

BACKGROUND

Research on the health benefits of cannabis has been limited because use remains restricted or illegal in most countries. Medical cannabis has been legal in Canada since 2001 and recreational use became legal in October 2018. While there are data that support a biological mechanism by which cannabinoids can impact various other symptoms of MS, the evidence of effectiveness of cannabis as a treatment for bladder symptoms remains unsettled. We conducted an exploratory study to describe the current trends of cannabis product consumption among people with MS (PwMS) and their association with perceived benefits on MS symptoms.

METHODS

A cross-sectional survey study of PwMS, recruited from the MS Clinic in Calgary, Alberta, Canada was undertaken. Logistic regression analyses were performed to assess the associations between cannabis consumption and improvement in bladder function symptoms.

RESULTS

There were 775 respondents out of 2899 PwMS contacted by email. Among respondents, 734 reported cannabis use in the past 3 months. There were 275 (37.5%) respondents who reported cannabis use in the prior 3 months, and 73.8% of these reported at least weekly use of cannabis. Among all users, 78.1% reported a primary medical or therapeutic indication for consumption. The most common modes of cannabis consumption were oral-edible (69.0%) and smoked (57.1%), while 59.3% used more than one mode of consumption and 2.6% used five different modes. The most common reasons for cannabis use were for sleep (58.3%), pain (51.5%), relaxation (44.4%), muscle spasms (40.2%), anxiety (33.8%) and depression (22.9%). Among the 19 participants who reported bladder symptoms as a main reason for cannabis use, 89.5% reported "better" bladder symptoms when using cannabis. Cannabis consumption in the past 3 months was associated with a two-fold increased odds of reporting improvement in urinary frequency, urinary urgency, bladder leakage and wetness, pad use and bladder emptying.

CONCLUSIONS

Cannabis is commonly used in this survey study of personal cannabis use among PwMS. Patterns of use, dosing, frequency and mode of delivery are diverse among survey respondents. This pilot study provides some initial glimpses into real world therapeutic use of cannabinoids among PwMS for bladder symptoms.

Immunomodulation by cannabinoids: Current uses, mechanisms, and identification of data gaps to be addressed for additional therapeutic application

The endocannabinoid system plays a critical role in immunity and therefore its components, including cannabinoid receptors 1 and 2 (CB₁ and CB₂), are putative druggable targets for immune-mediated diseases. Whether modulating endogenous cannabinoid levels or interacting with CB₁ or CB₂ receptors directly, cannabinoids or cannabinoid-based therapeutics (CBTs) show promise as anti-inflammatory or immune suppressive agents. Herein we provide an overview of cannabinoid effects in animals and humans that provide support for the use of CBTs in immune-mediated disease such as multiple sclerosis (MS), inflammatory bowel disease (IBD), asthma, arthritis, diabetes, human immunodeficiency virus (HIV), and HIV-associated neurocognitive disorder (HAND). This is not an exhaustive review of cannabinoid effects on immune responses, but rather provides: (1) key studies in which initial and/or novel observations were made in animal studies; (2) critical human studies including meta-analyses and randomized clinical trials (RCTs) in which CBTs have been assessed; and (3) evidence for the role of CB₁ or CB₂ receptors in immune-mediated diseases through genetic analyses of single nucleotide polymorphisms (SNPs) in the CNR1 and CNR2 genes that encode CB₁ or CB₂ receptors, respectively. Perhaps most importantly, we provide our view of data gaps that exist, which if addressed, would allow for more rigorous evaluation of the efficacy and risk to benefit ratio of the use of cannabinoids and/or CBTs for immune-mediated diseases.

A comprehensive review on the role of chemokines in the pathogenesis of multiple sclerosis

Multiple sclerosis (MS) as a chronic inflammatory disorder of the central nervous system (CNS) is thought to be caused by the abnormal induction of immune responses. Chemokines as molecules that can engage leukocytes into the location of inflammation, actively participate in the pathogenesis of MS. Several members of this family of chemo attractants have been shown to be dysregulated in the peripheral blood, cerebrospinal fluid or CNS lesions of MS patients. Studies in animal models of MS particularly experimental autoimmune encephalomyelitis have indicated the critical roles of chemokines in the pathophysiology of MS. In the current review, we summarize the data regarding the role of CCL2, CCL3, CCL4, CCL11, CCL20, CXCL1, CXCL2, CXCL8, CXCL10, CXCL12 and CXCL13 in the pathogenesis of MS.

The Effect of Cannabis on the Clinical and Cytokine Profiles in Patients with Multiple Sclerosis

Background

Multiple studies have reported that cannabis administration in multiple sclerosis patients is associated with decreased symptom severity. This study was conducted to evaluate the prevalence of cannabis abuse in multiple sclerosis cases and to evaluate the effect of cannabis on serum cytokines in such cases. Patients and Methods. A total of 150 multiple sclerosis cases along with 150 healthy controls were included during the study period. All cases were subjected to history taking, neurological examination, and routine investigations. Cases were asked about cannabis intake which was confirmed by a urine test. Serum cytokines including IL-1, IL-2, IL-4, IL-10, IL-12, IL-17, IL-22, IFN-γ, IFN-β1, and TNF-α were ordered for all cases and controls.

Results

Twenty-eight cases were cannabis abusers (MS/cannabis group, 18.67%). The remaining 122 cases represented the MS group. There was no significant difference between the three groups regarding age, disease duration, or MS type. Male gender was more predominant in the MS/cannabis group, and the number of relapses was significantly lower in the same group. Fifteen cases (53.6%) reported that their symptoms were improved by cannabis. Proinflammatory cytokines were significantly elevated in the MS group compared to the MS/cannabis and control groups. Additionally, anti-inflammatory cytokines had significantly lower values in the MS group compared to the MS/cannabis and control groups. Most clinical symptoms were significantly improved in the MS/cannabis group compared to the MS group apart from sexual dysfunction, bladder symptoms, and visual disturbances. Mild side effects of cannabis were also reported.

Conclusion

Cannabis may have a positive impact on the cytokine and clinical profiles in cases with multiple sclerosis.

Cannabis and Inflammatory Mediators

INTRODUCTION

Although the recreational cannabis use is expressive worldwide, the literature about medical potential of cannabis extracts, including its anti-inflammatory properties, remains inconclusive.

METHODS

We screened all articles, published on the PubMed database, on inflammatory mediators and any information about cannabis use from 1980 to March 2019.

RESULTS

Six studies were included, and the main findings were as follows: (i) among healthy volunteers and cannabis users, cannabinoids seemed to decrease the inflammatory response, thus decreasing the immune response, which led to a higher risk of infections; (ii) among patients with multiple sclerosis, cannabinoids seemed to have little impact on the inflammatory markers' levels.

DISCUSSION

Although cannabis use can produce immune inflammatory suppression in healthy people, this effect is not robust enough to change inflammatory mediators' levels in situations of highly dysfunctional inflammatory activation. Nevertheless, the impact of cannabinoids in clinical outcomes of these conditions remains to be determined.

Allostatic load and the cannabinoid system: implications for the treatment of physiological abnormalities in post-traumatic stress disorder (PTSD)

It is becoming clear that post-traumatic stress disorder (PTSD) is not simply a psychiatric disorder, but one that involves pervasive physiological impairments as well. These physiological disturbances deserve attention in any attempt at integrative treatment of PTSD that requires a focus beyond the PTSD symptoms themselves. The physiological disturbances in PTSD range over many systems, but a common thread thought to underlie them is that the chronic effects of PTSD involve problems with allostatic control mechanisms that result in an excess in what has been termed "allostatic load" (AL). A pharmacological approach to reducing AL would be valuable, but, because of the large range of physiological issues involved - including metabolic, inflammatory, and cardiovascular systems - it is unclear whether there exists a simple comprehensive way to address the AL landscape. In this paper, we propose that the cannabinoid system may offer just such an approach, and we outline evidence for the potential utility of cannabinoids in reducing many of the chronic physiological abnormalities seen in PTSD which are thought to be related to excess AL.

Associations of marijuana with markers of chronic lung disease in people living with HIV

OBJECTIVES

The relationship between marijuana use and markers of chronic lung disease in people living with HIV (PLWH) is poorly understood.

METHODS

We performed a cross-sectional analysis of the Examinations of HIV-Associated Lung Emphysema (EXHALE) study, including 162 HIV-positive patients and 138 participants without HIV. We modelled marijuana exposure as: (i) current daily or weekly marijuana smoking vs. monthly or less often; or (ii) cumulative marijuana smoking (joint-years). Linear and logistic regression estimated associations between marijuana exposure and markers of lung disease, adjusted for tobacco smoking and other factors.

RESULTS

In PLWH, current daily or weekly marijuana use was associated with a larger forced vital capacity (FVC), larger total lung capacity and increased odds of radiographic emphysema compared with marijuana non-smokers in adjusted models; these associations were not statistically significant in participants without HIV. Marijuana joint-years were associated with higher forced expiratory volume in 1 s and FVC in PLWH but not with emphysema.

CONCLUSIONS

In PLWH, marijuana smoking was associated with higher lung volumes and potentially with radiographic emphysema. No consistently negative associations were observed between marijuana and measures of chronic lung health.

Cannabis, the Endocannabinoid System and Immunity-the Journey from the Bedside to the Bench and Back

The Cannabis plant contains numerous components, including cannabinoids and other active molecules. The phyto-cannabinoid activity is mediated by the endocannabinoid system. Cannabinoids affect the nervous system and play significant roles in the regulation of the immune system. While Cannabis is not yet registered as a drug, the potential of cannabinoid-based medicines for the treatment of various conditions has led many countries to authorize their clinical use. However, the data from basic and medical research dedicated to medical Cannabis is currently limited. A variety of pathological conditions involve dysregulation of the immune system. For example, in cancer, immune surveillance and cancer immuno-editing result in immune tolerance. On the other hand, in autoimmune diseases increased immune activity causes tissue damage. Immuno-modulating therapies can regulate the immune system and therefore the immune-regulatory properties of cannabinoids, suggest their use in the therapy of immune related disorders. In this contemporary review, we discuss the roles of the endocannabinoid system in immunity and explore the emerging data about the effects of cannabinoids on the immune response in different pathologies. In addition, we discuss the complexities of using cannabinoid-based treatments in each of these conditions.

Cannabis in the Time of Coronavirus Disease 2019: The Yin and Yang of the Endocannabinoid System in Immunocompetence

Editor's Note: For those whose response to COVID-19 includes exploring beyond vaccines, conventional pharmaceuticals, and the watchful or healthy waiting until such tools might arrive, interest in cannabinoids has been high - and controversial. It has already stimulated one journal, the Liebert Cannabis and Cannabinoid Research, to issue a call for papers on COVID-19. The unique place of cannabis in the culture seems to always mark the herb with an exponential asterisk whenever basketed with the other natural health strategies that are both widely used, and as broadly derided. In this invited commentary, JACM Editorial Board member Michelle Sexton, ND starts by describing the multiple immune modulating effects associated with the herb. The University of California San Diego Assistant Adjunct Professor in Anesthesiology then asks: "Given these effects, can phytocannabinoids be either helpful, or harmful for immune competency, in the context of the current COVID-19 pandemic?" A skilled edge-walker, Sexton lets the research fall where it may in wending a path through this evidentiary maze. -John Weeks, Editor-in-Chief, JACM.

Integrating Endocannabinoid Signaling and Cannabinoids into the Biology and Treatment of Posttraumatic Stress Disorder

Exposure to stress is an undeniable, but in most cases surmountable, part of life. However, in certain individuals, exposure to severe or cumulative stressors can lead to an array of pathological conditions including posttraumatic stress disorder (PTSD), characterized by debilitating trauma-related intrusive thoughts, avoidance behaviors, hyperarousal, as well as depressed mood and anxiety. In the context of the rapidly changing political and legal landscape surrounding use of cannabis products in the USA, there has been a surge of public and research interest in the role of cannabinoids in the regulation of stress-related biological processes and in their potential therapeutic application for stress-related psychopathology. Here we review the current state of knowledge regarding the effects of cannabis and cannabinoids in PTSD and the preclinical and clinical literature on the effects of cannabinoids and endogenous cannabinoid signaling systems in the regulation of biological processes related to the pathogenesis of PTSD. Potential therapeutic implications of the reviewed literature are also discussed. Finally, we propose that a state of endocannabinoid deficiency could represent a stress susceptibility endophenotype predisposing to the development of trauma-related psychopathology and provide biologically plausible support for the self-medication hypotheses used to explain high rates of cannabis use in patients with trauma-related disorders.

Targeting Cannabinoid Signaling in the Immune System: "High"-ly Exciting Questions, Possibilities, and Challenges

It is well known that certain active ingredients of the plants of Cannabis genus, i.e., the "phytocannabinoids" [pCBs; e.g., (-)-trans-Δ⁹-tetrahydrocannabinol (THC), (-)-cannabidiol, etc.] can influence a wide array of biological processes, and the human body is able to produce endogenous analogs of these substances ["endocannabinoids" (eCB), e.g., arachidonoylethanolamine (anandamide, AEA), 2-arachidonoylglycerol (2-AG), etc.]. These ligands, together with multiple receptors (e.g., CB₁ and CB₂ cannabinoid receptors, etc.), and a complex enzyme and transporter apparatus involved in the synthesis and degradation of the ligands constitute the endocannabinoid system (ECS), a recently emerging regulator of several physiological processes. The ECS is widely expressed in the human body, including several members of the innate and adaptive immune system, where eCBs, as well as several pCBs were shown to deeply influence immune functions thereby regulating inflammation, autoimmunity, antitumor, as well as antipathogen immune responses, etc. Based on this knowledge, many in vitro and in vivo studies aimed at exploiting the putative therapeutic potential of cannabinoid signaling in inflammation-accompanied diseases (e.g., multiple sclerosis) or in organ transplantation, and to dissect the complex immunological effects of medical and "recreational" marijuana consumption. Thus, the objective of the current article is (i) to summarize the most recent findings of the field; (ii) to highlight the putative therapeutic potential of targeting cannabinoid signaling; (iii) to identify open questions and key challenges; and (iv) to suggest promising future directions for cannabinoid-based drug development.

Spasticity in multiple sclerosis: Contribution of inflammation, autoimmune mediated neuronal damage and therapeutic interventions

In contrast to other diseases that go along with spasticity (e.g. spinal cord injury), spasticity in chronic autoimmune diseases involving the CNS is complicated by the ongoing damage of neuronal networks that leads to permanent changes in the clinical picture of spasticity. Multiple sclerosis (MS) is the most frequent autoimmune disease of the central nervous system (CNS) and spasticity is one of the most disabling symptoms. It occurs in more than 80% MS patients at some point of the disease and is associated with impaired ambulation, pain and the development of contractures. Besides causing cumulative structural damage, neuroinflammation occurring in MS leads to dynamic changes in motor circuit function and muscle tone that are caused by cytokines, prostaglandins, reactive oxygen species and stress hormones that affect neuronal circuits and thereby spasticity. The situation is complicated further by the fact that therapeutics used for the immunotherapy of MS may worsen spasticity and drugs used for the symptomatic treatment of spasticity have been shown to have the potential to alter immune cell function and CNS autoimmunity itself. This review summarizes the current knowledge on the immunologic pathways that are involved in the development, maintenance, dynamic changes and pharmacological modulation of spasticity in MS.

Correlation of IL-17 Level in Synovia and Severity of Knee Osteoarthritis

Background

The aim of this study was to evaluate the role of interleukin-17 (IL-17) level in synovia and its relationship with the severity of knee osteoarthritis (OA).

Material/Methods

We enrolled 226 OA patients and 106 controls in this study. The symptomatic/radiation severity of OA was assessed by the Western Ontario McMaster University Osteoarthritis Index (WOMAC) pain score/Kellgren-Lawrence (KL) grading system. Serum IL-17 levels were measured by enzyme-linked immunosorbent assay (ELISA).

Results

Synovia IL-17 levels were significantly higher in OA patients compared with controls (P<0.01), and were negatively correlated with OA severity. IL-17 level gradually decreased among different phases but lacked statistical significance.

Conclusions

IL-17 might play a crucial role in the pathogenesis of OA and is closely related to pain. Blocking the IL-17 signaling pathway may delay pain related to OA.

Neuroprotection in Experimental Autoimmune Encephalomyelitis and Progressive Multiple Sclerosis by Cannabis-Based Cannabinoids

Multiple sclerosis (MS) is the major immune-mediated, demyelinating, neurodegenerative disease of the central nervous system. Compounds within cannabis, notably Δ9-tetrahydrocannabinol (Δ9-THC) can limit the inappropriate neurotransmissions that cause MS-related problems and medicinal cannabis is now licenced for the treatment of MS symptoms. However, the biology indicates that the endocannabinoid system may offer the potential to control other aspects of disease. Although there is limited evidence that the cannabinoids from cannabis are having significant immunosuppressive activities that will influence relapsing autoimmunity, we and others can experimentally demonstrate that they may limit neurodegeneration that drives progressive disability. Here we show that synthetic cannabidiol can slow down the accumulation of disability from the inflammatory penumbra during relapsing experimental autoimmune encephalomyelitis (EAE) in ABH mice, possibly via blockade of voltage-gated sodium channels. In addition, whilst non-sedating doses of Δ9-THC do not inhibit relapsing autoimmunity, they dose-dependently inhibit the accumulation of disability during EAE. They also appear to slow down clinical progression during MS in humans. Although a 3 year, phase III clinical trial did not detect a beneficial effect of oral Δ9-THC in progressive MS, a planned subgroup analysis of people with less disability who progressed more rapidly, demonstrated a significant slowing of progression by oral Δ9-THC compared to placebo. Whilst this may support the experimental and biological evidence for a neuroprotective effect by the endocannabinoid system in MS, it remains to be established whether this will be formally demonstrated in further trials of Δ9-THC/cannabis in progressive MS.