Introduction

Multiple Sclerosis (MS) is a chronic disorder that, most commonly, first manifests in adulthood. It is an autoimmune condition that affects the nervous system. The defence cells attack myelin, a protein with a fatty structure that covers parts of the neuron’s body. Myelin supports synapses, ensuring electrical pulses run smoothly and assertively through the neurons. The MS mechanisms affect nerve cells’ integrity and communication. Symptoms can be mild to severe, even debilitating and are usually episodic. Patients can experience vision problems, muscle weakness, dizziness, fatigue, and cognitive impairments during that period. A characteristic MS symptom that often follows the rest is pain. The disease progression can lead to atrophy in parts of the brain, leading to neurodegenerative disorders.¹

MS patients experience different types of pain, some directly caused by the disorder, others indirectly. For example, neuropathic pain is a result of MS mechanisms damaging the central nervous system. On the other hand, musculoskeletal pain is caused by an injury to bones or muscles, which MS patients usually experience with their muscle weakness, spasms, lack of balance and coordination problems. In both cases, pain can be felt either in acute episodes or chronic, for a prolonged time and recurrently. Treating the pain caused by multiple sclerosis can be challenging, as each case is different. People have different needs, different pain causes and different responses to medication. It is possible to manage to live with MS-related pain, but usually, the journey requires constant monitoring and changing approaches. Besides, many patients struggle to find a treatment that completely ceases the painful experiences; it is common to just reduce them.²

Cannabis products have been investigated and used for medical purposes for a while. Solid scientific evidence backs up its use as a treatment approach for several health conditions. Many hemp products commercialised can not attest to their medical efficacy, like cosmetics and supplements, but drugs based on hemp compounds have been produced and approved by regulatory organisations around the world; they require a doctor’s prescription. One of these established medications obtained from cannabis is a mouth spray for relieving muscle spasms associated with multiple sclerosis.³ Similar drugs have been explored for their benefits for patients who live with pain related to MS, with significant results and many adepts so far.⁴

Understanding MS-related pain

Neuropathic pain

Many MS patients experience neuropathic pain directly caused by the disorder. The immune system’s attack on the myelin and other parts of the neurons damages brain cells. When properly functioning, these cells send electrical signals to one another, which command the whole body. In impaired conditions, these signals are misinterpreted and end up being the root cause of severe neuropathic pain. It is of difficult management, usually refractory to treatment.²

Other pain types in MS

• Musculoskeletal pain: muscle and/or bone pain caused by injuries related to other MS symptoms (muscle weakness, loss of balance, dizziness, etc)
• Spasticity-related pain: abrupt and uncontrollable muscle contractions
• Inflammation: MS causes the body to experience inflammation, a characteristic of immune diseases. Inflamed tissue becomes more sensitive to pain

Cannabis compounds and their mechanisms

The human body has an Endocannabinoid System (ECS), which contains cannabinoid receptors and chemicals that stimulate them, the endocannabinoids. The ECS modulates several body responses like stress, anxiety, alertness, sleep, hunger, pain, memory, body temperature, inflammatory reactions, etc.^{5, 6}

During the synapse, chemicals are responsible for the electrical signals to pass from one neuron to another. Cannabis compounds, like THC and CBD, are structurally similar to the endocannabinoids, naturally present in the nervous and immune systems. They interfere with the effects of these chemicals, even blocking synapses. Intercepting pain signals is a mechanism that often improves MS-related pain.^{5, 6}

THC (Tetrahydrocannabinol)

• Psychoactive properties
• Benefits for pain relief
• Strongly binds to cannabinoid receptors widely spread in the central nervous system. The main receptors that are easily activated by THC cause a desensitising effect, being crucial in pain control mechanisms⁷

CBD (Cannabidiol)

• Mild to non-psychoactive
• Neuroprotective properties: anti-inflammatory, antioxidant
• More commonly, it binds to cannabinoid receptors in the immune system, modulating the inflammatory response⁷

Evidence on cannabis for MS-related pain

Studies that investigate the benefits of using cannabis for pain reduction and spasticity relief have shown significant and positive results. Many MS patients rely on such work to initiate treatment based on these compounds, resulting in adherence to this approach. Besides, younger MS patients tend to be more open to using cannabis as a medical tool, suggesting a slight and gradual growth in supporters within the population of multiple sclerosis. Despite the high interest, cannabinoid research still faces several obstacles that slow scientific progression.⁸

Limitations of current research

• Legal and regulatory challenges affecting research
• Small sample sizes
• Restricted variability in cannabis products

Risks and side effects of cannabis use in MS patients

• Short-term effects: dizziness, cognitive impairments, dry mouth
• Long-term effects: potential for dependency, psychiatric effects, and need for more research on long-term safety
• Contraindications and precautions: interaction with other medications, importance of medical supervision

Legal and accessibility considerations

Legal status of medical cannabis

Sativex, a THC-CBD extract developed by a UK pharmaceutical company, was approved by the local organisation for medical purposes in 2003. In 2010, Sativex obtained approval for MS treatment. It is one of the most recognised cannabinoid MS treatments and has also been regulated in countries like Canada (since 2005), Spain (2010), New Zealand (2010), and Germany (since 2011).⁷

FDA has approved drugs derived from cannabinoids for treating rare and severe types of epilepsy, nausea from chemotherapy and weight loss from AIDS and cancer. According to the regulation, these patients were not properly responsive to first-line medication. The US regulatory organisation has committed to facilitating processes for drugs of great interest, regardless of social stigma, under solid scientific evidence, but Sativex has not yet gained FDA approval.⁷

Patients depend on local laws and their rightful access to cannabinoid treatment. Even at the places it is approved, the process is strict and bureaucratic, ensuring that treatment is only allowed to those who need it and are unsuccessful with traditional drugs. Besides, public health policies may not cover costs for cannabis based treatment, which can be expensive.

Medical guidance and patient education

Healthcare providers need to be not only up to date with local legislation regarding the use of medical cannabis but also responsible for the required prescription and guiding safe use. As with any drug, the cannabinoid usage for MS-related pain must be supervised by a doctor. The health professional is the one able to tailor a treatment plan, taking into account the interaction of cannabis with other medications, individual and characteristic MS symptoms and expected response for the particular case.

Summary

Multiple Sclerosis is an autoimmune and chronic health disorder with characteristic painful symptoms. It triggers the immune system to attack brain cells and elements crucial for brain cells’ proper functioning. It can trigger neuropathy, pain originating from damaged neurons. Many patients struggle to find a treatment that adequately manages their condition to improve their quality of life. Cannabis is a promising treatment option for MS-related pain. The plant’s chemical compounds, especially THC and CBD, activate receptors in the immune and nervous systems that relieve inflammation and sensitivity to pain. Studies show positive results regarding the use of cannabinoids for the treatment of MS-related pain, which backs up laws in different regions to approve such use. A lot of bureaucracy and stigma around cannabis slow down scientific advances in the area. There is a need for further research, requiring more comprehensive, large-scale studies, as many MS patients are not properly responsive to conventional treatment. It is important to balance out the approach alongside a health professional, evaluating potential benefits with risks and legal considerations.