Introduction

Chronic pain lasts for more than three to six months, and it can be constant or come and go. Chronic pain can affect any part of the body and include feelings such as prickling, tingling, stinging, burning, or aching. It can be caused by various factors such as injuries, diseases, infections, arthritis, cancer, and even emotional or environmental factors. Living with chronic pain can make it hard to work, eat well, exercise, or enjoy everyday activities. Additionally, chronic pain can lead to feelings of sadness and loneliness, making it difficult to connect with others. Overall, chronic pain can significantly impact a person’s quality of life.¹

Cannabis is increasingly used for pain management due to its interaction with the endocannabinoid system. The endocannabinoid system is a complex network found throughout the body, playing key roles in regulating pain, mood, appetite, sleep, and more. It includes cannabinoid receptors (CB1 and CB2) and natural compounds called endocannabinoids, which help manage pain and inflammation. Cannabis contains cannabinoids, including tetrahydrocannabinol (THC) and cannabidiol (CBD), which can relieve different types of pain. 

Cannabis can be consumed in various forms, such as smoking, edibles, or oils. While it can be effective, users should be aware of potential side effects, such as dizziness and tolerance, as well as the legal status of cannabis in their area.²

Types of chronic pain

Neuropathic pain

Neuropathic pain arises due to damage or dysfunction in the nervous system. It is classified into 2 categories: peripheral and central. It includes feelings such as: ¹

• Burning
• Tingling
• electric shock-like sensations
• numbness and hypersensitivity to touch (in some cases)

Musculoskeletal pain

Musculoskeletal pain occurs due to different reasons, such as:¹

• Injuries: Like sprains or strains
• Chronic conditions: Like arthritis
• Repetitive use: This pain generally affects muscles, bones, tendons, ligaments, and joints

People with musculoskeletal pain usually suffer from:

• Aching
• Stiffness
• Soreness

Inflammatory pain

Inflammatory pain is caused by inflammation due to tissue damage. Inflammatory conditions can be due to:¹

• Acute injuries
• Infections
• Chronic conditions, such as rheumatoid arthritis or lupus

Inflammatory pain can worsen with movement and be sharp and accompanied by:

• Swelling
• Redness
• Heat in the affected area

Nociceptive pain

Nociceptive pain is commonly a protective response to injury caused by damage to body tissues. Nociceptive pain can be acute (short-term) or chronic (lasting longer than three months), depending on the cause, which could include:¹

• Burns
• Cuts 
• Sprains
• Bruises

Nociceptive pain can be sharp or throbbing and usually diminishes as the injury heals.¹

Visceral pain

Visceral pain starts from internal organs and normally spreads more than other types of pain. Visceral pain arises from conditions affecting the heart, lungs, digestive system, or other internal organs, such as gallbladder disease or heart attacks. Visceral pain symptoms usually include: ¹

• Deep, pressure-like pain
• Cramping
• Nausea 
• Sweating

Psychogenic pain 

Instead of physical injury, emotional and psychological factors are the main cause of psychogenic pain. Conditions including depression, anxiety and stress can present as physical pain, which can range in different intensities. Psychogenic pain is generally described as:¹

• Headaches
• Back pain
• Stomach aches

Cancer pain

Cancer pain results from cancer, cancer treatment-related (such as surgery or chemotherapy), or complications associated with the disease (spread of cancer). Depending upon the type of cancer, pain can range from dull and aching to sharp and intense.¹

Cannabis

There are two types of cannabis plants found: Cannabis indica and Cannabis sativa. Cannabis indica is shorter with broad, dark green leaves and has higher levels of cannabidiol (CBD). On the other hand, Cannabis sativa is taller with thin, pale green leaves and has higher levels of tetrahydrocannabinol (THC). Cannabis plants contain approximately 426 chemical compounds, including about 60 cannabinoids, of which THC and CBD are the most studied. 

THC and CBD can have opposite effects. For example, THC can cause anxiety, impair memory, and increase heart rate. On the other hand, CBD can reduce anxiety and prevent psychotic symptoms caused by THC. Imaging studies indicate that THC and CBD activate different areas of the brain, highlighting their contrasting influences on cognition and emotion. 

THC is known for its psychoactive effects (affects mood, thoughts, feelings and behaviour), while CBD offers therapeutic benefits. In some studies, CBD was beneficial for conditions including inflammation, diabetes, and neurodegenerative diseases.^3,4

The role of cannabis in managing chronic pain

Neuropathic and central pain 

Several studies have examined the use of cannabis in the treatment of neuropathic pain. The overall findings indicate that smoked or inhaled cannabis in its floral form is effective whether used alone or as an adjunct therapy for alleviating neuropathic pain from various causes. Numerous studies also highlight additional advantages, such as improved sleep and enhanced functioning. However, side effects are prevalent, particularly at higher doses, and may include difficulties with concentration, dizziness, fatigue, and increased heart rate. More severe reported side effects encompass anxiety, paranoia, and psychosis.^5,6

Musculoskeletal pain

The application of cannabis for addressing chronic musculoskeletal pain is still a topic of debate. Although there have been studies assessing its safety and effectiveness for non-cancer chronic pain linked to conditions such as fibromyalgia, multiple sclerosis, headaches, and spinal cord injuries, the research on medical cannabis for chronic, non-cancer musculoskeletal pain is minimal. 

A small number of randomised controlled trials that explored the safety and efficacy of cannabinoids for pain related to rheumatic diseases have yielded mixed outcomes and did not show a clear advantage over control groups. Drawing any conclusions about the effectiveness of cannabis for managing chronic musculoskeletal pain is challenging due to the available data, but the safety profile appears to be promising.^6,7

Fibromyalgia

Fibromyalgia is a chronic condition involving pain, tenderness, and stiffness in the muscles, ligaments, and tendons throughout the body, often occurring with symptoms including fatigue, sleep disturbances, headaches, and mood disorders such as depression and anxiety. Numerous research efforts have explored the potential of medical cannabis in alleviating fibromyalgia symptoms, including pain, sleep issues, and fatigue. With a significant margin of safety and anticipated regulatory impacts of THC and CBD on key endogenous pain pathways, cannabis is becoming a promising alternative for managing chronic pain.⁸

Summary

Chronic pain lasts longer than three to six months and can occur anywhere in the body, causing sensations like prickling, tingling, or aching. It can stem from various causes such as injuries, diseases, and emotional factors, negatively impacting daily activities and overall quality of life. Cannabis is being explored for pain management due to its effects on the endocannabinoid system, which helps regulate pain. It contains cannabinoids like THC and CBD, which can relieve pain but may have side effects.

Chronic pain types include neuropathic pain (due to nervous system damage), musculoskeletal pain (from injuries or chronic conditions), inflammatory pain (caused by tissue damage), nociceptive pain (from injuries), visceral pain (from internal organs), psychogenic pain (caused by emotional factors), and cancer pain linked to cancer or its treatments. Cannabis plants come in two types: Cannabis indica and Cannabis sativa, each with different characteristics. THC is psychoactive and can cause side effects, while CBD is known for its therapeutic effects. Studies show potential benefits of cannabis for neuropathic pain, though findings regarding its effectiveness for musculoskeletal pain are mixed. Research suggests that cannabis could effectively help manage symptoms of fibromyalgia, making it a promising option for chronic pain relief.