The Science of the Endocannabinoid System
How THC and CBD tap into the body's balancing system.
Posted October 29, 2025 | Reviewed by Margaret Foley
Cannabis, once a symbol of rebellion and counterculture, is now one of the most commonly used recreational substances. The plant’s primary psychoactive compounds, THC (tetrahydrocannabinol) and CBD ( cannabidiol ), act on one of the body’s most widespread neurotransmitter systems. The endocannabinoid and the CB1 and CB2 receptors don't work in the usual way we think of. Whereas GABA and Glutamate directly decrease or increase activity in neurons through the opening of pores on the cell's surface, and serotonin and dopamine influence a neuron's reactivity through receptors on the postsynaptic surface, CB1 and CB2 receptors work in almost the reverse way.
This post is not about THC and CBD (we will talk about how they work), it's about the endocannabinoid system itself. We will discuss the unusual nature of this system. The CB1 receptor is found all over the central nervous system . The CB2 receptor is found on peripheral organs like the GI tract and on immune cells.
The CB1 Receptor and the Brain’s Inner Balance
The endocannabinoid system (ECS) is not unique to humans; it appears across the animal kingdom, from fish to mammals, and always with the same purpose: to maintain homeostasis. It does so through molecules our own cells produce on demand, called endocannabinoids, the best-known being anandamide (also found in chocolate) and 2-arachidonoylglycerol (2-AG). Unlike classic neurotransmitters such as dopamine or serotonin, these compounds are made only when needed, acting as real-time regulators rather than continuous messengers.
What makes CB1 receptors especially fascinating is their presynaptic location. They sit on the ends of axons that send messages to neurons, as opposed to most other receptors, which are on the receiving neuron. When activated, they act like a brake, reducing the release of neurotransmitters, preventing excess release.
THC activates the CB1 receptor by acting as a partial agonist, meaning that it stimulates it but not to its fullest degree. CBD changes the shape of the CB1 receptor to reduce the ability of endocannabinoids and THC to activate it. CBD also decreased the breakdown of anandamide, steadying endocannabinoid levels throughout the brain, preventing spikes and falls.
CB1 receptors are found all over the brain, especially in the hippocampus (governing memory ), nucleus accumbens (managing reward and reinforcement), basal ganglia and cerebellum (for coordinating movement), and the prefrontal cortex (the seat of higher cognition ). When THC activates CB1 receptors, it decreases the activity in each of these regions, causing memory issues, lack of coordination, and foggy thinking.
CB2: The Body’s Quiet Guardian
CB2 receptors operate in the immune cells, spleen, gastrointestinal tract, and peripheral nerves. Their role is to regulate inflammation. When activated, they reduce the release of inflammatory molecules called cytokines and help guide immune cells toward repair rather than attack. CB2 receptors are found in the brain but not on neurons; they are located on the brain’s immune cells called microglia, acting as a neuroprotective system, calming overactive immune responses and helping neurons recover from inflammation. In the GI tract, they lower local inflammation and stabilize permeability, improving our absorption and digestion of food.
THC and CBD both interact with the CB2 receptors in functionally similar ways to their interaction with CB1 receptors. THC is a partial agonist (like on CB1 receptors), lightly stimulating CB2 and decreasing inflammatory activity, which contributes to the physical relaxation and pain relief many experience. CBD functions as a modulator, enhancing the receptor’s natural anti-inflammatory capacities and supporting tissue repair.
The Endocannabinoid System in Modern Medicine
Both THC and CBD have transitioned from folk remedies to evidence-based therapeutics. THC is the main psychoactive compound and acts on CB1 and CB2 receptors to reduce pain, nausea, and muscle spasticity. It is FDA-approved in modified forms called dronabinol and nabilone for chemotherapy-related nausea and HIV/AIDS-related appetite loss. It is used clinically for neuropathic pain and spasticity in multiple sclerosis.
CBD, in contrast, produces no intoxication and acts largely through indirect modulation of the endocannabinoid and serotonin systems. A purified formulation called Epidiolex is FDA-approved for rare childhood epilepsies such as Lennox-Gastaut and Dravet syndromes. Research also supports potential benefits for anxiety , sleep, inflammatory pain, and neuroprotection, though most applications remain investigational.
Cannabis has gone from a symbol of rebellion to a doorway into understanding how the body keeps itself in balance. The endocannabinoid system is built for balance. It helps the brain and body from drifting too far into overactivation. Knowing how it works lets us see cannabis not as magic or menace, but as a reminder of how finely tuned our biology already is.
Capodice, J. L., & Kaplan, S. A. (2021, June). The endocannabinoid system, cannabis, and Cannabidiol: Implications in urology and Men’s Health. Current urology. https://pmc.ncbi.nlm.nih.gov/articles/PMC8221009/?utm
Cooray, R., Gupta, V., & Suphioglu, C. (2020, August 19). Current aspects of the endocannabinoid system and targeted THC and CBD phytocannabinoids as potential therapeutics for parkinson’s and alzheimer’s diseases: A review. Molecular neurobiology . SpringerLink. https://link.springer.com/article/10.1007/s12035-020-02054-6?utm
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Jason Shimiaie, M.D., is an assistant clinical professor at Mount Sinai Hospital. He researches relational psychoanalysis, trauma, and dissociation.
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This article is part of the Bringwise Psychology Journal — daily insights on human behavior, mental health, and personal growth.