Short answer
Cannabis reduces chronic pain for some patients. The evidence is strongest for nerve pain and for pain that has not responded to other treatments. It is not a first-line option. The FDA has not approved a cannabis product for chronic pain. Doctors who certify patients in state programs work from limited trial data.
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What the evidence shows
A 2017 report by the National Academies of Sciences, Engineering, and Medicine reviewed more than 10,000 abstracts. It found substantial evidence that cannabis or cannabinoids reduce chronic pain in adults. That is the strongest conclusion in the report for any condition besides chemotherapy-induced nausea.
medical marijuana for chronic pain management
Cochrane reviews of neuropathic pain rate most trials as low quality. Sample sizes run from 20 to 250 patients. Most trials last 2 to 15 weeks. No large trial has followed patients for years.
medical marijuana for chronic pain management
Chronic pain is common. CDC data from 2016 put 20.4% of US adults with chronic pain, about 50 million people. High-impact chronic pain, the kind that limits daily activity, affected 7.4%.
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How THC and CBD work
THC binds CB1 receptors in the brain, spinal cord, and peripheral nerves. CB1 receptors sit on pain-signaling pathways. Binding reduces the signal. CBD binds CB1 with low strength. CBD may act on other targets, including serotonin receptors and inflammatory pathways.
Effects vary by person. Body weight, tolerance, liver enzyme activity, and prior use all change the response.
Forms and onset times
- Inhaled flower or vape: onset 2 to 10 minutes. Effects last 2 to 4 hours.
- Oral oil, tincture, capsule, or edible: onset 30 to 120 minutes. Effects last 4 to 8 hours.
- Topical cream: no psychoactive effect. Evidence for joint pain is thin.
Oral products pass through the liver. The liver converts THC to 11-hydroxy-THC, a compound with stronger psychoactive effects. This step raises the risk of a bad reaction when a patient takes too much.
Dosing
- Start at 1 to 2.5 mg THC per dose.
- Wait 2 hours for oral products before adding more.
- Increase by 1 to 2.5 mg every 3 to 7 days.
- Stop at the dose that cuts pain without heavy sedation.
Many patients use less THC with added CBD. A 1:1 ratio of THC to CBD is a common starting point. CBD does not block the THC high, but it may reduce anxiety and rapid heart rate.
Side effects and risks
- Dizziness, drowsiness, dry mouth
- Short-term memory problems
- Fast heart rate
- Impaired driving for 4 to 6 hours after inhalation
NIDA reports that about 30% of cannabis users develop some degree of cannabis use disorder. Risk rises with daily use and high THC concentrations.
Cannabis affects CYP450 enzymes. It can raise or lower blood levels of warfarin, clobazam, some HIV drugs, and some antidepressants. Tell your prescriber about every drug you take.
Legal status
Cannabis is Schedule I under federal law. Most states with medical programs require a physician certification and a state card. Rules, possession limits, and product testing standards differ by state.