People have used cannabis to self-medicate for headache for thousands of years. Previous research indicates that approximately 1/3 of current medical cannabis users report using cannabis to manage headache and migraine pain and when these patients were asked how well cannabis works to alleviate such pain, they reported an average 36% reduction in headache pain from cannabis (Sexton et al., 2016).
Other research has found that 40% of patients recommended medical cannabis reported that it benefited them and that the frequency of their migraines decreased by more than 50% (Rhyne et al., 2016). Finally, a previous clinical trial revealed that nabilone (a synthetic cannabinoid) was more effective than ibuprofen at reducing the intensity of headache and patients who used nabilone reduced their use of other pain relievers and reported an increased quality of life (Pini et al, 2012). These studies suggest that many individuals use cannabis to manage head pain and that they experience some therapeutic effects. Nevertheless, despite the common use of cannabis for head pain few studies have examined the acute effects of cannabis on headache and migraine and none have examined potential predictors of relief from head pain following cannabis use.
The primary purpose of the present study was to conduct a large-scale naturalistic investigation of the acute effects of cannabis on headache and migraine. First, we sought to determine whether headache and migraine severity would be significantly reduced after inhaling cannabis. Second, we sought to examine potential predictors of such relief, including concentrations of tetrahydrocannabinol (THC) and cannabidiol (CBD), dose of cannabis used, type of cannabis used (flower versus concentrates), and gender of the user. Third, we explored whether tolerance to the therapeutic effects of cannabis on headache or migraine would develop over time. Finally, we investigated whether medical cannabis users would demonstrate evidence of medication overuse headache, by examining whether the baseline (pre-cannabis use) severity of headache or migraine changed over time.
To achieve our objectives, we obtained global back-data from the Canadian-based medical cannabis tracking application, Strainprint®. The Strainprint app provides medical cannabis patients with the ability to indicate the conditions and symptoms that they use cannabis to manage, to rate their baseline symptom severity immediately before cannabis use, to indicate the strain of cannabis they are about to use and the producer of the cannabis, as well as to indicate their method of administration and the dose of cannabis used. Approximately 20 minutes after their cannabis inhalation session, participants are prompted via push notification to re-rate the severity of their symptom(s). Importantly, information on the THC and CBD concentrations of the cannabis used could be obtained in two ways: 1) inputted by the app users, 2) pulled directly from the Canadian producers' websites.
We obtained anonymous (i.e., de-identified) data from over 1,800 medical cannabis users who collectively used the app over 22,000 times to track changes in headache severity from before to after cannabis use and from over 1,000 medical cannabis patients who used the app over 14,000 times to track changes in migraine severity over a period of 16 months. Given the potential for disparate effects stemming from different methods of administration we opted to only analyze data from sessions in which users indicated inhaling cannabis and to try to better capture the period of intoxication after inhaling cannabis we limited analyses to sessions for which symptoms were re-rated within 4 hours of cannabis use. Finally, we only analyzed data from which the THC and CBD concentrations were obtained directly from Canadian producers' websites. The final sample contained over 1,300 medical cannabis users who collectively used the Strainprint® app over 12,000 times to track changes in headache and over 600 medical cannabis users who used the app over 7,000 times to track changes in migraine from before to after inhaling cannabis.
First, we examined the overall percentage of sessions for which headache and migraine severity ratings reduced after using cannabis. The results revealed that patients reported decreases in headache severity in 90% of all tracked sessions and decreases in migraine severity in 88% of tracked sessions. These results indicate that for the vast majority of inhaled cannabis sessions, medical cannabis users experience a reduction in the severity of their head pain. Second, we examined the magnitude of symptom reduction and found that, on average, headache severity ratings were reduced by 47% and migraine symptom severity ratings were reduced by 49.5%. These results indicate that medical cannabis cuts the severity of head pain in half.
Next, we examined predictors of symptom relief. Somewhat surprisingly, despite the very large sample size and the ample statistical power such a large sample provides we found no significant predictors of reductions in migraine severity ratings. This indicates that cannabis reduces migraine severity regardless of the gender of the user or the type, dose, THC or CBD content of the cannabis used. In contrast, we found that gender of the user, type of cannabis used, and time predicted reductions in headache severity. More specifically, the results revealed that while both genders reported significant symptom relief, men reported significantly larger reductions in headache severity following cannabis use than did women. Next, while both cannabis flower and concentrates significantly reduced headache severity, cannabis concentrates produced significantly larger reductions in headache than did more traditional cannabis flower. Finally, time was a significant predictor of reductions in headache severity, with larger reductions reported for earlier cannabis use sessions and smaller reductions reported for later cannabis use sessions across the 16-month time period of the study. This indicates that users may develop some tolerance to the therapeutic effects of cannabis on headache over time.
We also examined changes in dose of cannabis used to manage headache and migraine over the 16-month time period of the study and found that dose of cannabis used to treat headache remained static over time. In contrast, the dose used to treat migraine appeared to increase across time, suggesting users may be developing some tolerance and require larger does to achieve the same beneficial effects on migraine over time.
Finally, given the prominence of medication overuse headache associated with more conventional treatments we attempted to explore evidence for its development by examining changes in baseline severity ratings over time. The results revealed no changes in the baseline severity ratings of headache nor migraine over time which suggests these cannabis users were not developing the medication overuse headache associated with more conventional treatments.
The results of this large-scale naturalistic examination of medical cannabis users revealed that medical cannabis users experienced headache and migraine symptom relief on approximately 90% of cannabis treatment sessions. Moreover, the magnitude of these reductions was substantial, with users reporting, on average, nearly 50% reductions in headache and migraine severity ratings after inhaling cannabis.
While both cannabis flower and cannabis concentrates produced substantial and significant reductions in headache severity ratings, concentrates were associated with significantly larger reductions than cannabis flower. Cannabis concentrates are typically of much higher potency than cannabis flower, with THC concentrations exceeding as much as 90% in some concentrates while the maximum concentration of THC in flower rarely exceeds 30%. While it is tempting to attribute the greater efficacy of concentrates to their potency, despite ample statistical power we surprisingly failed to find any evidence that concentrations of THC or CBD predicted symptom relief. As such it is currently unclear why concentrates were associated with larger reductions in reported headache severity. This is one of the first studies to examine relative health effects of cannabis concentrates to cannabis flower and as such future more controlled research is needed to understand the relative effects of these two types of products.
We examined evidence of tolerance to the effects of cannabis on headache and migraine developing over time in two ways. First, we examined whether users were reporting less symptom relief over the 16-month duration of the study. Second, we examined whether patients escalated their dose over this period of time. With respect to headache results showed that users reported consistent doses but diminishing symptom relief over time. The opposite pattern was observed for migraine, with dose increasing over time and efficacy remaining static over time. Nevertheless, collectively these results indicate some development of tolerance developing over time.
Finally, given that most conventional medications are associated with medication overuse headache – a phenomenon marked by increased frequency and severity of headache over time as a function of medication use – we further explored changes in baseline severity ratings over time. We found that baseline severity of headache and migraine remained stable over time which suggests cannabis is not associated with the medication overuse headache that limits many more conventional treatments. Nevertheless, we were not able to examine whether headaches became more frequent over time and as such this is still a possible side effect of cannabis use that will need to be explored using more controlled research.
This study has important limitations that should be acknowledged. First, the self-selected sample of medical cannabis users likely over-represents individuals who find cannabis an effective medicine, as users who do not experience benefit would likely cease cannabis use and cease tracking such use with the Strainprint® app. Most importantly however the study lacked a placebo control group and in its absence it is not possible to determine the extent to which the findings represent a placebo/expectancy effect. Nevertheless, these limitations are offset by a number of strengths including the use of a very large sample of medical cannabis patients using a wide variety of cannabis products in their own environment which increases the ability to generalize the results to other medical cannabis patients using cannabis in their own environment to manage headache and migraine.