Sufferers reported a reduction of 47 percent in the severity of headaches and 49 percent in migraine pain.
Although many people use cannabis for pain relief, very few studies have researched it. One clinical trial concluded that cannabis was more effective than ibuprofen.
Researchers from Washington State University recruited 1,300 who suffer from frequent headaches and 653 migraine sufferers. They all used an app to report when they suffered an attack, when they took cannabis and the effect it had, in 'real time'. In all, the two groups lodged nearly 20,000 reports.
There was no reporting of 'overuse headache', where headaches can become more severe over time and is often seen with more conventional treatments, although the researchers noted that the participants were starting to take larger doses, suggesting they were developing a tolerance to the drug.
Although cannabis oil was a more effective pain-reliever than the cannabis flower, the researchers said the different levels of THC (tetrahydrocannabinol) and CBD (cannabidiol) used by the participants wasn't a factor.