Cannabinoids are chemical compounds that interact with a built-in signaling network in your body called the endocannabinoid system. Through this system, they influence pain, mood, appetite, immune function, memory, and movement. Some cannabinoids are produced naturally by your body, some come from the cannabis plant, and others are made synthetically in a lab. What they all share is the ability to plug into the same set of receptors and alter how your cells communicate.
Your Body’s Built-In Cannabinoid System
Your body produces its own cannabinoids, called endocannabinoids, as part of normal cell signaling. The two main ones are anandamide and 2-AG. These molecules are made on demand when cells need to send a message, then quickly broken down by specialized enzymes once the job is done. Anandamide is dismantled by an enzyme called FAAH, while 2-AG is primarily cleared by a different enzyme called MAGL. This rapid creation and destruction keeps the system tightly regulated.
These endocannabinoids work by binding to two types of receptors scattered throughout your body: CB1 and CB2. CB1 receptors are among the most plentiful receptors in the brain, concentrated in areas that control movement, memory, cognition, and pain processing. They also appear at lower levels in the heart, lungs, liver, and reproductive organs. CB2 receptors, by contrast, are found mainly in immune tissues like the spleen, tonsils, and white blood cells, where they help regulate inflammation. CB2 receptors can also appear in the brain during disease states like Alzheimer’s and multiple sclerosis, suggesting the system ramps up its immune response when the brain is under stress.
How Cannabinoids Change Cell Signaling
Cannabinoids work through a mechanism that runs in reverse compared to most brain signaling. Normally, a sending nerve cell releases chemical messengers that travel forward to a receiving cell. With cannabinoids, the process flips. The receiving cell produces endocannabinoids that travel backward to the sending cell, where they bind to CB1 receptors and tell it to quiet down. This “retrograde signaling” acts like a volume knob, dialing back the release of other chemical messengers.
This backward signal can suppress both excitatory and inhibitory messengers. When it reduces excitatory signaling, neural activity slows down. When it reduces inhibitory signaling, certain circuits actually become more active. The net effect depends on which brain region is involved and which type of synapse the cannabinoid reaches. This is why cannabinoids can simultaneously relax muscles, alter pain perception, impair short-term memory, and stimulate appetite: they’re adjusting the volume on many different circuits at once.
These adjustments can be brief, lasting just seconds, or they can become longer-lasting changes that reshape how a synapse behaves over time. Short-term effects involve directly limiting calcium flow into nerve terminals, which prevents messenger release. Longer-term effects involve deeper changes to the cell’s internal signaling machinery, essentially reprogramming how strongly that synapse fires going forward.
THC vs. CBD: Two Very Different Compounds
The cannabis plant produces over 100 cannabinoids, but THC and CBD are by far the most studied. They behave very differently at the molecular level. THC binds directly and snugly to CB1 receptors in the brain, with a binding strength roughly 100 times greater than CBD’s. This tight fit is what produces the intoxicating “high,” along with effects like pain relief, increased appetite, and altered time perception.
CBD has very weak binding at both CB1 and CB2 receptors and does not produce intoxication. Instead, it appears to work through several indirect routes. It slows the breakdown of anandamide by interfering with the enzyme that degrades it, effectively boosting your body’s own cannabinoid levels. CBD also influences pain and temperature-sensing channels on nerve cells and modulates inflammatory pathways. In immune cells, CBD dials down the production of inflammatory signaling molecules by blocking a key activation pathway called NF-κB, which helps explain its anti-inflammatory reputation.
A lesser-known cannabinoid called CBG (cannabigerol) is gaining research attention. CBG partially activates CB2 receptors, interacts with several pain and temperature-sensing channels, and slows the breakdown of anandamide, similar to CBD. In animal studies, CBG improved motor function in mice with a model of Huntington’s disease, reduced gut inflammation in a colitis model, and lowered pain sensitivity in mice with chemotherapy-related nerve damage. These results are preliminary and haven’t been confirmed in human trials.
Effects on Pain
Pain relief is one of the most common reasons people use cannabinoids, and the evidence is real but modest. A large meta-analysis published in JAMA that pooled data from multiple clinical trials found that cannabinoids produced a statistically significant reduction in pain scores, but the average improvement on a 0-to-10 pain scale was less than half a point compared to placebo. For the percentage of patients who achieved meaningful relief (a 30% or greater reduction in pain), 37% of cannabinoid users hit that threshold versus 31% on placebo.
Neuropathic pain, the burning or shooting pain caused by nerve damage, showed a somewhat better response. Trials lasting 5 to 15 weeks found a roughly 4-point improvement on a 0-to-100 neuropathic pain scale. These numbers suggest cannabinoids can help some people with chronic pain, particularly nerve-related pain, but they’re not a dramatic fix for most patients. The effects tend to be comparable to or slightly less than those of established pain medications.
Effects on the Immune System
Because CB2 receptors are concentrated in immune tissues, cannabinoids have a meaningful influence on immune function. CB2 receptors become more abundant when immune cells are activated and inflammation is present, which means the system is designed to respond more strongly during illness or injury. Activating these receptors generally pushes the immune response in an anti-inflammatory direction.
CBD in particular has been studied for its ability to reduce inflammation in the gut. It works by modulating multiple signaling pathways inside immune cells, reducing the output of pro-inflammatory molecules. This has implications for conditions like inflammatory bowel disease, though most of this evidence comes from cell and animal studies rather than large human trials.
FDA-Approved Cannabinoid Medications
Four cannabinoid-based medications currently have FDA approval. Epidiolex, which contains purified CBD derived from the cannabis plant, is approved for treating seizures in patients two years and older with Lennox-Gastaut syndrome or Dravet syndrome, two severe forms of epilepsy. It remains the only FDA-approved drug made directly from cannabis.
The other three are synthetic. Marinol and Syndros both contain dronabinol, a lab-made version of THC, approved for nausea from cancer chemotherapy and appetite loss in AIDS patients. Cesamet contains nabilone, a compound with a chemical structure similar to THC, also approved for chemotherapy-related nausea. No cannabis product (as distinct from individual cannabinoid drugs) has received FDA approval for any condition.
How Your Body Processes Cannabinoids
Your liver breaks down cannabinoids using the same enzyme family that metabolizes many common medications. CBD is processed primarily by two liver enzymes, CYP2C19 and CYP3A4, with CYP2C9 also playing a role. This matters because CBD can interfere with these same enzymes when they’re trying to process other drugs, effectively causing those medications to build up to higher-than-expected levels in your bloodstream.
The interactions can be clinically significant. In patients taking the blood thinner warfarin, CBD use has been shown to increase warfarin’s effects, raising the risk of bleeding. In epilepsy patients taking clobazam alongside CBD, blood levels of clobazam’s active byproduct increased more than threefold. And in transplant patients on tacrolimus (an immune-suppressing drug), adding CBD tripled the drug’s concentration. If you take prescription medications, these interactions are worth knowing about before using CBD products.
Risks of Heavy or Long-Term Use
Cannabinoid hyperemesis syndrome (CHS) is a condition that develops in some people after years of regular cannabis use. It causes cycles of severe nausea, vomiting, and abdominal pain that repeat every few weeks to months. A distinctive feature is that sufferers often find temporary relief only from prolonged hot showers or baths, a behavior so characteristic that clinicians consider it nearly diagnostic.
Formal diagnostic criteria require that symptoms follow a pattern resembling cyclical vomiting, that they develop after prolonged and heavy cannabis use, and that they resolve completely after quitting cannabis (confirmed by a negative drug test). Symptoms must be present for at least three months, with onset at least six months before diagnosis. CHS is frequently misdiagnosed because many patients and clinicians don’t initially connect vomiting with cannabis use, since cannabinoids are better known for suppressing nausea than causing it.
Beyond CHS, regular THC use carries risks of dependence, cognitive impairment (particularly with use before age 25, when the brain is still developing), and worsening of anxiety or psychotic symptoms in susceptible individuals. Because CB1 receptors are so densely concentrated in brain areas governing memory and cognition, heavy long-term use can measurably affect these functions, though much of the impairment appears to improve after sustained abstinence.