Cannabinoids in Cannabis: What They Do and What the Evidence Shows
Cannabis contains more than 100 biologically active compounds, including phytocannabinoids that can interact with the body’s endocannabinoid system. The best known are delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), but lesser-studied compounds such as cannabigerol (CBG), tetrahydrocannabivarin (THCV), cannabichromene (CBC), and cannabinol (CBN) are also attracting scientific interest.
A comprehensive 2017 review by the National Academies of Sciences, Engineering, and Medicine concluded that some cannabis-based treatments can help with specific symptoms, while also emphasizing that evidence varies considerably by condition, product, dose, and route of administration.
The major cannabinoids
THC is the primary intoxicating compound in cannabis. It activates cannabinoid receptors—particularly CB1 receptors in the brain—and can produce euphoria, altered perception, impaired coordination, and changes in memory. THC also has established medical uses in some prescription products, including the treatment of chemotherapy-related nausea and vomiting and appetite loss associated with AIDS-related weight loss. Its potential benefits must be weighed against adverse effects such as dizziness, drowsiness, confusion, and impaired judgment.
CBD does not produce the characteristic cannabis “high.” It interacts only weakly with CB1 and CB2 receptors and affects several other biological targets. Although CBD is widely marketed for anxiety, inflammation, pain, and neurodegenerative disease, those claims are not equally supported by clinical evidence. In the United States, the Food and Drug Administration has approved purified CBD as Epidiolex for seizures associated with Lennox-Gastaut syndrome, Dravet syndrome, and tuberous sclerosis complex. That approval applies to a specific prescription medicine—not to CBD products generally.
CBG, or cannabigerol, is sometimes called a precursor cannabinoid because its acidic form contributes to the production of THC, CBD, and other compounds in the plant. Laboratory and animal studies have examined CBG’s possible antibacterial, anti-inflammatory, and neuroprotective properties. However, evidence from well-controlled human trials remains limited, so CBG should be regarded as an experimental compound rather than an established treatment for conditions such as multiple sclerosis or Huntington’s disease.
THCV resembles THC chemically but can have different effects at cannabinoid receptors, including antagonistic or blocking activity at CB1 receptors under some conditions. This has prompted interest in appetite, glucose metabolism, and obesity research. Early findings do not establish THCV as a proven weight-loss treatment, and results from laboratory studies should not be treated as evidence that commercially sold THCV products are effective or safe for that purpose.
CBC and CBN are also under investigation. CBC has shown analgesic, anti-inflammatory, and mood-related effects in preclinical research, while CBN is produced as THC breaks down and is often marketed as a sleep aid. Claims about CBN’s sedative effects, however, have not been firmly established in rigorous human studies. For both compounds, much of the evidence still comes from laboratory or animal research rather than clinical trials.
How the endocannabinoid system works
The endocannabinoid system is a network of signaling molecules, receptors, and enzymes that helps regulate processes such as pain perception, appetite, mood, memory, immune activity, and sleep. The body produces its own endocannabinoids, including anandamide and 2-arachidonoylglycerol, which activate cannabinoid receptors when needed.
CB1 receptors are concentrated in the central nervous system, although they are also found in several peripheral tissues. CB2 receptors are more closely associated with immune cells and peripheral tissues, though both receptor types can occur in multiple parts of the body. Their distribution helps explain why cannabinoids can affect such a wide range of functions.
THC activates CB1 receptors directly, contributing to both its intoxicating effects and some of its therapeutic actions. CBD behaves differently: it has low direct affinity for CB1 and CB2 and appears to influence several receptor systems and enzymes rather than acting like THC at a single target. The pharmacology of minor cannabinoids is even more complex and remains an active area of research.
What the clinical evidence shows
Research supports cannabinoid-based medicines for some specific uses. Reviews of randomized trials have found evidence for benefits in chemotherapy-induced nausea and vomiting, certain forms of chronic pain, and spasticity associated with multiple sclerosis, although the size of benefit and certainty of evidence differ among conditions. A systematic review of systematic reviews found that cannabinoids may help some patients, but also reported frequent adverse effects and less consistent results in larger or longer studies.
These findings do not mean that cannabis treats every condition for which it is marketed. Evidence for depression, Alzheimer’s disease, Parkinson’s disease, obesity, and many inflammatory or neurodegenerative disorders remains preliminary or insufficient. Results from cell cultures and animal models can identify promising mechanisms, but they cannot establish effectiveness in people.
Product quality is another important consideration. Cannabis preparations can differ substantially in their concentrations of THC, CBD, minor cannabinoids, and aromatic compounds known as terpenes. Labels may not always accurately reflect the contents, and unapproved products have not undergone the same testing required of prescription medicines. Cannabis and cannabinoid products can also interact with other drugs and may cause impairment or other unwanted effects.
Cannabinoid science therefore offers genuine medical possibilities, but its most reliable lessons are specific rather than sweeping: some standardized cannabinoid medicines can be useful for particular symptoms, while many claims surrounding individual compounds remain unproven. Continued clinical research—especially well-designed trials of minor cannabinoids and combinations of cannabinoids with terpenes—will be necessary to determine which treatments are safe, effective, and appropriate for patients.
