A new type of drug could relieve pain like marijuana does without affecting the brain, according to a new study.

Researchers from Imperial College London looked at two kinds of receptors in the nervous system, known as CB1 and CB2. Marijuana activates those receptors, blocking pain signals. But because CB1 receptors are found in the brain as well as other parts of the body, blocking them affects the brain.

Blocking the CB2s could stop pain without clouding thinking or leading to abuse and dependency, researchers wrote.

"Although cannabis is probably best known as an illegal recreational drug, people have used it for medicinal purposes for centuries. Queen Victoria used it in tea to help with her period pains, and people with a variety of conditions say that it helps alleviate their symptoms," principal investigator Praveen Anand in a news release. "Our new study is very promising because it suggests that we could alleviate pain by targeting the cannabinoid receptor CB2 without causing the kinds of side-effects we associate with people using cannabis itself."

The researchers reached their conclusions after studying human sensory nerve cells in culture with CB2 receptor compounds provided by GlaxoSmithKline as well as injured nerves from patients with chronic pain.

The work was published in the journal Pain.