Tetrahydrocannabinol, or THC, is the chemical compound in the marijuana plant that makes you high. Cannabidiol, or CBD, is the second most prevalent active chemical in cannabis, but it does not make you high. Both have been associated with pain relief.
“The findings are in line with what we know,” said Yasmin Hurd, a professor of pharmacological sciences, neuroscience and psychiatry at the Icahn School of Medicine at Mount Sinai in New York City. She was not involved with the study.
“There is some indication of weak-to-moderate pain relief depending on the THC/CBD ratio, but there is an increase of side effects such as dizziness and sedation,” said Hurd, who is the director of the Addiction Institute at Mount Sinai.
However, no such benefits were found from any over-the-counter THC or CBD extracts from the whole marijuana plant.
“Unfortunately, the available evidence is largely inconclusive, due to the small number of studies and the variation in cannabinoid products among these studies,” said Jodi Gilman, an associate professor at the Center for Addiction Medicine at Harvard Medical School who was not involved with the study.
“Large, placebo-controlled trials in hundreds of patients who are all taking the same exact product at the same doses are needed to understand the benefits and risks of cannabis for chronic pain,” Gilman added.
No benefit from nonprescription extracts
The review analyzed 25 clinical trials and observational studies involving nearly 15,000 people. The prescription drugs dronabinol, made of pure synthetic THC, and nabilone, which is nearly pure THC, were linked to moderate improvements in pain relief, but an increased risk of drowsiness and dizziness, researchers found.
Nabiximols, a drug with comparable amounts of THC and CBD designed to be sprayed under the tongue, improved pain relief and function to a smaller degree but also carried a risk for sedation, dizziness and nausea, according to the study published Monday in the Annals of Internal Medicine. Nabiximols is a prescription drug that is not available in the United States.
Those side effects caused some patients to stop using the products, even though they “are also common side effects of other pain medications,” Gilman said.
Patients using cannabinoids for pain should be “closely monitored by their doctors in order to determine whether these products are helpful,” Gilman said, and determine if any benefit outweighs potential side effects.
“While the amount of pain relief is not substantial, individuals suffering from chronic pain might think that it is worth the risk. Clearly, CBD has a much greater safety profile than THC so it is important that high-THC products be carefully monitored,” Hurd said.
“It is critical that patients consider conventional clinically approved products before trying cannabis,” she said. “Also, they have to be extremely careful regarding what cannabis products they use since there are a lot of products that do not have good quality control and might not even contain the amount of THC or CBD they think based on the packaging.”
In addition, Hurd warned, “it is not suitable to smoke ‘recreational’ cannabis as medicine.” Just like tobacco, smoking weed can damage the lungs and increase the risk of respiratory diseases. Heavy cannabis use has been associated with increased risk of heart attacks, she said.