Delta-9-tetrahydrocannabinol
THC
The main intoxicating compound in cannabis. It drives most of what people mean by "high," and it is also the cannabinoid behind most documented therapeutic effects.
Evidence status
NASEM 2017 found conclusive or substantial evidence for cannabis in chronic pain in adults, and for oral cannabinoids as antiemetics in chemotherapy-induced nausea and vomiting and for patient-reported MS spasticity.
THC binds directly to CB1 receptors, which are concentrated in the brain and central nervous system. That direct binding is why THC is intoxicating and why it produces effects on pain perception, appetite, nausea, and sleep — and also why it produces anxiety, rapid heart rate, and impaired short-term memory when the dose is too high.
The dose-response curve for THC is not a straight line. For anxiety in particular, low doses often reduce it and higher doses reliably make it worse. This is the single most common reason a first cannabis experience goes badly: the person took more, expecting more relief, and got the opposite.
Two FDA-approved medicines are synthetic THC: dronabinol (Marinol, approved 1985; Syndros oral solution, approved 2016), indicated for chemotherapy-induced nausea and vomiting and for appetite loss in AIDS. A third, nabilone (Cesamet, approved 1985), is a synthetic cannabinoid indicated for chemotherapy-induced nausea. Their existence is the clearest evidence that cannabinoid pharmacology is real medicine in specific, narrow indications.
Commonly used for
- • Chronic pain in adults
- • Chemotherapy-induced nausea and vomiting
- • Multiple sclerosis spasticity (patient-reported)
- • Appetite stimulation
Cautions
- • Intoxicating — do not drive or operate machinery.
- • Higher doses commonly increase anxiety rather than reduce it.
- • THC inhibits CYP2C9 and has documented interactions with warfarin, including case reports of INR above 4.6 and above 10.
- • Avoid during pregnancy and breastfeeding.
Conditions where THC is part of the suggested profile
- Chronic painPain lasting more than three months. The single indication with the strongest evidence base for cannabis in adults.
- Chemotherapy-induced nausea and vomitingNausea and vomiting caused by chemotherapy. One of three indications with substantial evidence, and the basis for two FDA-approved medicines.
- Multiple sclerosis spasticityMuscle stiffness and spasm in multiple sclerosis. Substantial evidence for patient-reported improvement; weaker for clinician-measured.
- Sleep disturbanceDifficulty falling or staying asleep. Moderate evidence — but only for sleep disturbance tied to specific underlying conditions.
- Appetite loss with HIV/AIDSLoss of appetite and weight in HIV/AIDS. Limited evidence, and the basis for one of dronabinol's FDA indications.
- PTSDPost-traumatic stress disorder. Limited evidence resting on a single small trial — and a qualifying condition in many state medical programs regardless.
- Tourette syndromeTic disorder. Limited evidence for THC capsules.
- FibromyalgiaWidespread pain with fatigue and sleep disruption. Covered indirectly by the chronic pain and sleep findings.
- Neuropathic painPain from nerve damage — burning, shooting, or electric in quality. Covered by the chronic pain finding.
- ArthritisJoint pain and inflammation. Covered by the chronic pain finding.
- MigraineRecurrent severe headache. Insufficient evidence specifically for migraine, despite widespread claims.
- Nausea (general)Nausea not caused by chemotherapy. The strong evidence is specific to chemotherapy — this is weaker ground.
- Muscle spasmsInvoluntary muscle contraction. Evidence is strongest in MS spasticity; weaker for spasms from other causes.
- IBS and inflammatory bowel diseaseDigestive conditions with pain and disrupted bowel function. Symptom relief may help; disease activity does not appear to change.
- Menstrual crampsPainful periods. No condition-specific evidence; covered loosely by chronic pain.
- Back painPersistent back pain. Covered by the chronic pain finding once it is chronic.
- Cancer-related painPain associated with cancer or its treatment. Covered by chronic pain; cannabis does not treat cancer.
Sources
- National Academies of Sciences, Engineering, and Medicine. The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research. Washington, DC: The National Academies Press, 2017.(DOI 10.17226/24625)Accessed 2026-08-15.
- NASEM 2017, Committee Conclusions (summary PDF of all evidence-tier conclusions).Accessed 2026-08-15.
- U.S. Food and Drug Administration. FDA Regulation of Cannabis and Cannabis-Derived Products, Including Cannabidiol (CBD).Accessed 2026-08-15.
- Damkier P, Lassen D, Christensen MMH, Madsen KG, Hellfritzsch M, Pottegård A. Interaction between warfarin and cannabis. Basic & Clinical Pharmacology & Toxicology. 2019;124(1):28-31.(DOI 10.1111/bcpt.13152 / PMID 30326170)Accessed 2026-08-15.