The Endocannabinoid System
The human body contains a complex cell-signalling network called the endocannabinoid system (ECS). First identified by researchers in the 1990s, the ECS plays a crucial role in regulating a wide range of physiological functions including pain, mood, sleep, appetite, immune response, and memory.
The ECS comprises three core components: endocannabinoids (naturally produced cannabinoids), receptors, and enzymes that break down cannabinoids once they have done their job.
Cannabinoid Receptors: CB1 and CB2
Two primary receptors make up the backbone of the ECS:
- CB1 receptors are found predominantly in the brain and central nervous system. They influence pain perception, mood, memory, movement, and appetite.
- CB2 receptors are found mainly in peripheral tissues and immune cells. They play a key role in inflammation and immune response.
Plant-derived cannabinoids (phytocannabinoids) from the cannabis plant interact with these receptors in ways that can modulate pain, anxiety, inflammation, and other symptoms.
THC: The Psychoactive Cannabinoid
Delta-9-tetrahydrocannabinol (THC) is the primary psychoactive compound in cannabis. It binds directly to CB1 receptors, producing its characteristic effects on mood and perception. In medical use, THC is valued for its ability to reduce pain, suppress nausea, stimulate appetite, and aid sleep. It is the main active ingredient in Sativex.
CBD: The Non-Intoxicating Cannabinoid
Cannabidiol (CBD) does not bind strongly to CB1 or CB2 receptors and produces no intoxicating effects. Instead, it interacts with multiple receptor systems including serotonin, vanilloid, and GPR55 receptors. CBD has demonstrated anti-inflammatory, anxiolytic, anticonvulsant, and neuroprotective properties in research. Epidyolex, a pharmaceutical-grade CBD, is licensed for childhood epilepsy.
The Entourage Effect
Full-spectrum cannabis products contain dozens of cannabinoids, terpenes, and flavonoids that may work synergistically — a phenomenon known as the entourage effect. Research suggests that whole-plant extracts may be more effective than isolated cannabinoids in some contexts, though the evidence is still developing.
Minor Cannabinoids: CBG, CBN, THCV and More
Beyond THC and CBD, cannabis contains over 100 identified cannabinoids, many with promising medical properties:
- CBG (cannabigerol) — potential antibacterial, anti-inflammatory, and neuroprotective properties
- CBN (cannabinol) — mild sedative properties, may support sleep
- THCV (tetrahydrocannabivarin) — appetite suppression, potential metabolic benefits
- CBDA (cannabidiolic acid) — anti-nausea effects being studied
Terpenes: More Than Just Aroma
Terpenes are aromatic compounds found in cannabis (and many other plants) that contribute to both the smell and the therapeutic character of a strain. Common terpenes include:
- Myrcene — sedating, muscle-relaxing
- Limonene — uplifting, anxiolytic
- Caryophyllene — anti-inflammatory (uniquely, it also binds to CB2 receptors)
- Pinene — alertness, memory retention
- Linalool — calming, anti-anxiety
Current Research in the UK
The UK is home to some of the world's leading medical cannabis research institutions. Project Twenty21, run by Drug Science, is one of the largest real-world evidence studies of medical cannabis anywhere in the world. The International Cannabis and Cannabinoids Institute (ICCI) and Sapphire Medical Clinics are also generating important clinical data that is shaping prescribing practice and informing NICE guidelines.