It’s pretty common for patients to turn to cannabis to treat migraines and headaches. In fact headache treatment is one of the most ancient uses of medical cannabis, finding application in ancient Greece and Persia. But modern researchers aren’t so sure about its efficacy—some suggest that it can even cause migraines.

Migraines are a little bit different than headaches. While severe headache is one aspect of a migraine, they are often accompanied by nausea, vomiting, sensory distortions and sensitivity to light and sound. Researchers generally agree that cannabis helps relieve headache pain and it seems that the drug helps with migraines at least in the short run.

A study published in the Journal of Integrative Medicine in 2020 found indications that cannabis relieves headache symptoms. The study analyzed 699 patient responses to a questionnaire given between 2016 and 2019. Patients were instructed to record headache pain intensity changes on a scale of 0-10 both before and after consuming cannabis.

According to the authors, 94 percent of participants experienced headache symptom relief within a two-hour period of using marijuana. The average reduction of symptoms was 3.3 points on the ten-point scale. More effective symptom relief was associated with cannabis containing THC levels of 10 percent or higher.

A 2020 study published in the Journal of Pain analyzed data from 12,293 patient questionnaire responses following sessions where cannabis was used to treat headaches and 7,441 sessions where it was used to treat migraines.

The authors said cannabis was found to have reduced the symptoms in 89.9 percent of the headaches and 88.1 percent of the migraines. Respondents reported a 47.3 percent decrease in headache severity and a 49.6 percent decrease in migraine severity. The level of symptom relief was not found to be affected by differences in cannabis strain or cannabinoid profile.

Rebounds

But a 2021 preliminary study from Stanford University School of Medicine researchers found that medical cannabis patients who use the drug to treat migraines could suffer from “rebound” headaches—medication overuse headaches.

“Many people with chronic migraine are already self-medicating with cannabis, and there is some evidence that cannabis can help treat other types of chronic pain,” said study author Niushen Zhang. “However, we found that people who were using cannabis had significantly increased odds of also having medication overuse headache, or rebound headache, compared to people who were not using cannabis.”

The study examined the medical records of 368 people who had chronic migraine for at least a year. Chronic migraine is defined as experiencing migraine symptoms at least 15 days in a month. Of the participants, 150 of the people used cannabis and 218 did not.

Of the 368 people, 212 experienced medication-overuse headaches. The study found that those who used cannabis were six times more likely to have medication-overuse headache than those who did not.

It’s unclear what the correlation is, but previous research has reportedly shown that cannabis can influence the periaqueductal gray. This area of the brain has been linked to migraines.