The Short Answer
Cannabis can reduce some types of pain. The evidence is strongest for chronic pain in adults and for spasticity from multiple sclerosis. Evidence for neuropathic pain is weaker, and evidence for acute pain is mixed. THC drives most of the pain relief measured in trials. CBD alone has fewer human pain studies than THC.
Cannabis for Analgesic Purposes: What the Evidence Shows
THC and CBD Target Different Receptors
THC binds CB1 and CB2 receptors in the endocannabinoid system. CB1 receptors sit in the brain, spinal cord, and peripheral nerves. Binding at those sites changes how the body signals pain. CBD binds CB1 with low affinity. CBD may raise anandamide levels by blocking the enzyme FAAH. Most CBD pain research uses animal models or small human samples.
Conditions Studied
- Chronic non-cancer pain: a 2017 National Academies review found substantial evidence for relief.
- MS spasticity: nabiximols, an oral spray with THC and CBD, lowered spasticity scores. Cochrane rated the evidence moderate.
- Neuropathic pain: Cochrane rated cannabinoid evidence low quality. Measured effects were small.
- Chemotherapy-induced nausea: a separate use. FDA-approved synthetic THC products cover it.
- Arthritis: topical CBD tested in small trials. Results are mixed.
Doses Used in Research
Trials use different doses. Nabiximols studies used 2.5 mg to 120 mg THC per day, split across sprays. Oral THC trials used 2.5 mg to 30 mg per dose. Epidiolex, an FDA-approved CBD drug for seizures, uses 10 mg to 20 mg per kg per day. No standard CBD dose exists for pain.
Forms and Timing
- Inhaled flower or vapor: onset 1 to 10 minutes, peak 15 to 30 minutes, effect 2 to 4 hours.
- Oral oil or capsule: onset 30 to 90 minutes, peak 2 to 4 hours, effect 6 to 8 hours.
- Topical: acts at the application site. Blood levels stay low.
Bioavailability differs by route. Inhaled THC delivers 10 to 35 percent of the dose. Oral THC delivers 4 to 20 percent. Liver enzymes convert oral THC to 11-hydroxy-THC, a compound with stronger effects. That conversion explains why oral doses hit harder and last longer.
Risks and Drug Interactions
- Side effects: dizziness, drowsiness, dry mouth, short-term memory changes.
- CBD inhibits CYP2C19 and CYP3A4 enzymes. It can raise blood levels of warfarin, clobazam, and some statins.
- THC can raise heart rate. A clinician should review use with heart disease or a history of psychosis.
- Cohort studies link high THC doses in adolescence to cognitive effects.
Legal Status in the US
Cannabis with more than 0.3 percent delta-9 THC is Schedule I under federal law. Many states allow medical or adult use, and state rules differ on sales, age limits, and testing. Hemp-derived CBD at 0.3 percent THC or less is legal under the 2018 Farm Bill. Labels on unregulated products list wrong cannabinoid amounts in many tests.
What to Check on a CBD or Cannabis Product
- A lab report with a batch number.
- Cannabinoid content in mg per serving.
- Test results for pesticides, heavy metals, and solvents.
- Delta-9 THC percentage, if you face drug testing.
Open questions remain. Research has not set a dose range for CBD in pain, and most trials last under 12 weeks. Long-term data on daily use is limited.