THC resembles the cannabinoid chemicals that occur naturally in the body. When people ingest or inhale THC, it stimulates the brain's cannabinoid receptors.
This activates the brain's reward system and reduces pain levels. THC is a psychoactive compound as it binds to cannabinoid receptors and produces an elevated state of mind, known as a high.
CBD does not cause a high, although it does interact with pain receptors in the brain to exert pain-relieving and anti-inflammatory effects.
What Research Says
In recent years, many studies have looked at the effects of marijuana for chronic pain. Some studies used parts of the marijuana plant and some have used the entire plant so more research is needed. Using parts of the marijuana plant (like CBD oil) helps study specific actions of that ingredient, but when the whole plant is used there is what is called an entourage effect, where the parts work together to have more effect.
A 2015 review of research on the use of marijuana and cannabinoids for various chronic pain conditions reports that several trials had positive results. The researchers suggest that marijuana or cannabinoids may be effective for treating some types of chronic pain including neuropathy (nerve pain).
A research paper from 2016 found that marijuana use for cancer pain led to a 64-percent reduction in opioid use, improved quality of life, and caused fewer medication side effects. It also led to participants using fewer medications.
Smaller studies have reported benefits for other types of chronic pain. For example:
Of about 17,000 people with cancer, 70 percent reportedly experienced an improvement in pain and general well-being after marijuana use.
However, there is still a need for more research into the area of marijuana use for chronic pain, especially into the use of different strains, dosages, and methods of delivery.
An Australian study, published in July 2018, concluded that marijuana use did not reduce the symptoms of pain or the need to use opioid medications. However, the findings were mostly based on reports from people who used the drug recreationally.
Using marijuana specifically for medicinal purposes might yield different results.