The hype: Cannabis oil is often heralded as a treatment to destroy or shrink cancerous tumors, as well as a cure for diabetes, ulcers, arthritis, migraines, insomnia, infections, and many other diseases. Also called marijuana oil or hemp oil, it’s extracted from marijuana plants, often with higher proportion of a compound known as CBD (cannabidiol), which has less of a psychoactive effect than the more-famous THC (tetrahydrocannabinol) compound that gets marijuana users high.
Cannabis oil is available in several forms with different potencies. It can be infused into cooking oil that users squirt under the tongue or mix into food. Its vapors can also be inhaled. By federal law, cannabis products are illegal, though several states have enacted laws to legalize their medical use.
The evidence: While commercially available cannabis compounds are FDA-approved to reduce cancer treatment–related side effects such as nausea and vomiting and to improve appetite, no clinical trials have shown that cannabis products can treat cancer.
Claims that cannabis oil cures cancer are anecdotal and largely unsupportable, based on scant research done in mice and in labs. Side effects can include memory and attention loss. Perhaps most important, there is evidence that cannabis compounds may inhibit enzymes that patients need to metabolize other anticancer drugs, thereby increasing their toxicity or reducing their effectiveness.
The verdict: “So far, there are no human studies that show cannabis oil can be used as cancer treatment,” Dr. Yeung says. “Patients who are using it — or any form of marijuana — should let their doctors know so they can advise you properly.”