Twenty-one adults with chronic nerve pain were taught to take a single inhalation of 25 milligrams of cannabis through a pipe, three times a day, for five days. The cannabis contained one of three levels of potency of tetrahydrocannabinol (THC), the active ingredient in marijuana, as well as a placebo dosage containing no THC.

All of the patients rotated through each of the four dosages, with nine days of no smoking in between.

Patients smoking the highest potency marijuana (9.4%) reported less pain than those smoking samples containing no THC. Patients also reported better sleep and less anxiety, according to the Canadian study. 

On an 11-point scale, the average daily pain intensity was 6.1 for those smoking 9.4% THC concentration, compared to 5.4 for those smoking cannabis containing no THC.

“Patients have repeatedly made claims that smoked cannabis helps to treat pain, but the issue for me had always been the lack of clinical research to support that claim,” said Dr. Mark Ware, director of clinical research at the Alan Edwards Pain Management Unit of the McGill University Health Centre in Montreal. In this small but randomized, controlled trial, “the pain reductions were modest, but significant,” he said. “And it was in people for whom nothing else worked.”

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