Introduction

Multiple sclerosis (MS) affects more than 150,000 individuals in the UK and 2.5 million people worldwide. MS is a chronic condition that affects your brain and spinal cord (central nervous system).¹ MS is an autoimmune disease, which means your body’s immune system starts attacking its own normal cells by mistake (Johns Hopkins Medicine). Other causes include environmental or genetic factors, or infections from Epstein-Barr virus.¹ Myelin is an important protein that creates a sheath around nerve cells and helps in the communication of signals between brain regions. Your body’s immune system mistakes myelin as a foreign object or threat and starts damaging the normal nerve cell structure; this leads to a number of neurological symptoms including problems with vision, balance, bladder and bowel function, memory and thinking, and emotions. Cannabis sativa, or cannabis, is a widely known plant used as an illicit drug. Cannabis contains a group of plant chemicals called cannabinoids, which are responsible for the feeling of euphoria or pain relief. Cannabis has been explored for its therapeutic effects and some doctors prescribe cannabis-based medications or medicinal cannabis to treat severe conditions. For example, some doctors prescribe a cannabis-based drug for the treatment of muscle spasms and stiffness (spasticity) symptoms in MS. The present article will explore the effects of cannabis on cognitive function in individuals affected by MS. 

Cognitive dysfunction in MS

In MS, your immune system dispatches T cells to eliminate the supposed threat and starts attacking the myelin sheath (inflammation and demyelination) in the nerve cells of the brain and spinal cord; this leads to scarring of nerve cells in the form of lesions or plaques, and this scarred tissue is called sclerosis; this damage leads to improper messaging and communication between nerve cells and leads to cognitive difficulties in memory, attention, judgment, and concentration.¹ Around 50 to 66 percent of individuals experience cognitive impairment in MS. Experiencing cognitive difficulties can greatly impact your quality of life and result in reduced life expectancy.¹ MS can disrupt your independent ability to go about your daily life, including walking or driving, and mood changes can strain personal and professional relationships, and often lead to depression in affected individuals.

The role of cannabis on cognitive function in MS

Cannabis contains a number of plant chemicals called cannabinoids, which have been widely studied for their medicinal value. The most well-known cannabinoids are THC (tetrahydrocannabinol) and CBD (cannabidiol). THC is known to produce a feeling of euphoria (psychoactive), whereas CBD does not produce this effect (non-psychotropic).² Cannabis provides relief for pain, spasticity, and disturbed sleep symptoms in MS; this is because cannabis has anti-inflammatory and immunosuppressive effects that act on the CB1 and CB2 receptors, which are distributed around the central and peripheral nervous systems in the body.² THC primarily acts on the CB1 receptors and inhibits the release of neurochemicals and blocks the pain pathways in the brain and spinal cord.CBD binds to CB1 and CB2 receptors, as well as transmembrane G-coupled protein receptors (GCPRs), to reduce pain, stiffness, fatigue, inflammation, and depression symptoms.² 

Licensed cannabis-based medications for MS

The UK prescribes three licensed cannabis-based medications, namely:

• Epidiolex
• Nabilone
• Sativex or Nabiximols

Of the three, Nabiximols is the only licensed drug approved to specifically treat moderate to severe symptoms of muscle spasm and stiffness, if other treatments are unsuccessful. Nabiximols is administered as an oral sprayand contains a 1:1 ratio of THC and CBD molecules.² A 2017 review by NASEM found that oral sprays provided pain relief for MS patients’ spasticity symptoms.³ Additionally, Nabiximols was found to improve patient quality of life.² Although Nabiximols provided relief from spasticity, pain, and sleep disorders, it has little effect on improving bladder dysfunction, and is unsuccessful in treating ataxia and tremor symptoms in MS.² Patients are advised to administer up to 12 sprays maximum per day for an initial 14-day period, with at least 15 minutes between each spray.²

Potential risks of cannabis usage in MS

It is imperative to understand both positive and negative effects of cannabis usage. Depending on the dosage, type, and quantities of THC or CBD in the products, common side effects include:²

• Dizziness or light-headedness
• Gastrointestinal issues, including nausea, diarrhoea, vomiting
• Dryness of the mouth
• Urinary tract infections
• Fatigue (extreme sense of tiredness and lack of energy)
• Drowsiness
• Headaches
• Disturbed attention and disorientation

The most prevalent side effects of taking Nabiximols were dizziness and fatigue.² Taking high doses of cannabis can cause fluctuations in your heart rate, blood pressure, reduce reaction time, and affect visual and physical abilities. Those with a personal or family history of mental health issues, including schizophrenia, must refrain from cannabis usage because it can trigger symptoms or worsen the condition. Furthermore, affected individuals who regularly smoke cannabis were found to show slower information processing and worse performance in memory tests. Improper usage of cannabis can worsen your recovery and cause relapses or progress your condition.

High THC levels affect basic motor coordination, and the ability to reason, plan, organise, make decisions, problem-solve, remember, and the ability to control emotions and behaviour.⁴ Acute effects occur 0 to 6 hours after smoking cannabis, whereas long-term effects persist 3 weeks or longer since the last usage.⁴ Acute effects impact your information processing, attention and concentration, decision-making and risk-taking, impulsivity, and working memory.⁴ Long-term effects include decision-making, concept formation, and planning, with mixed effects on verbal fluency.⁴

Legal and ethical considerations

Nabiximols or Sativex has been licensed and approved as a treatment for MS in Europe, UK, and Canada, but is not legally approved in the United States.³ In the UK, Sativex is a Class B controlled drug, which means it can be legally prescribed by specialist clinicians to individuals with an exceptional clinical need. If you are experiencing symptoms of MS, it is important to seek medical professional help and receive the appropriate prescription for the use of cannabis-based medications to balance symptom relief and potential side effects for treatment. 

Summary

Multiple sclerosis (MS) is a chronic autoimmune condition that affects more than 150,000 individuals in the UK and 2.5 million people worldwide. In MS, your body’s immune system mistakenly attacks the myelin in the nerve cells of your brain and spinal cord. It causes scarring of nerve cells in the form of lesions or plaques, and this scarred tissue is called sclerosis; this leads to neurological symptoms such as vision, balance, bladder and bowel function, memory and thinking, and emotions. 

Cannabis is a plant species known for its therapeutic effects due to the activity of plant chemicals or cannabinoids called THC and CBD. These cannabinoids act on nerve cell receptors like CB1, CB2, and GCPRs to block pain pathways and reduce pain, stiffness, fatigue, inflammation, and depression symptoms in MS. 

Nabiximols is the only licensed drug approved to specifically treat moderate to severe symptoms of muscle spasm and stiffness, and it is administered as an oral spray that contains a 1:1 ratio of THC and CBD. It is advised to follow up to 12 sprays maximum per day for an initial 14-day period, with at least 15 minutes between each spray. The most prevalent side effects of taking Nabiximols was dizziness and fatigue. 

Improper usage of cannabis can worsen your recovery and cause relapses or further progress your condition. Acute effects of smoking cannabis impact your information processing, attention and concentration, decision-making and risk-taking, impulsivity, and working memory. Long-term effects include decision-making, concept formation, and planning, with mixed effects on verbal fluency. If you are experiencing symptoms of MS, it is important to seek medical professional help and receive the appropriate prescription for the use of cannabis-based medications to balance symptom relief and potential side effects for treatment.