Cluster headaches can be extremely difficult to treat with standard therapy. As a result, some sufferers have turned to cannabis to relieve these and other types of refractory headaches.
Although medical research is scarce and inconclusive, some studies have found that cannabis can relieve cluster headaches. This suggests that the body’s endocannabinoid system (ECS) may be involved.
So far, researchers have found that the ECS may affect three processes believed to underlie cluster headaches. However, much of this evidence is indirect or comes from studies of migraines, so more research looking specifically at ECS function in cluster headaches is essential.
Read on for a detailed look at what research has uncovered about the endocannabinoid system, cluster headaches, and cannabis treatment.
Research on cluster headaches and cannabis
Only a few studies have looked at the use of cannabis for relieving cluster headaches, but their findings are promising.
Most notably, a 2014 study looked at 18 chronic cluster headaches sufferers who tried cannabis after failing to find sufficient relief from standard treatment. Most of them chose to smoke cannabis with an average daily dose of 1 gram. The researchers contacted the participants 2 months to 3 years after they started taking cannabis.
They found that 15 people (83%) experienced a 50% or greater reduction in headache severity, while 11 (61%) saw a 90%–100% reduction. Also, nine people (50%) noted an 80-100% decrease in headache frequency. Additionally, 11 of the participants (61%) reported high satisfaction from using cannabis, highlighted by reduced usage of prescription medication and improvement of sleep and quality of life.
Meanwhile, a 2009 report discussed the case of a 19-year-old student whose cluster headaches ceased through the use of cannabis, after failing to find relief with standard medications. He saw benefits from smoking whole-plant cannabis and later on from taking dronabinol, a synthetic drug form of tetrahydrocannabinol (THC).
However, some studies have reported less promising results. For example, a 2016 study of 139 French cluster headache patients looked at 27 (19.4%) of them who used cannabis to relieve headaches. Of these individuals, 26% reported some benefits, such as stopping the headache or promoting relaxation, while 52% noted variable or uncertain effects, and the remaining 22% reported negative effects (headaches/pain getting worse).
Several studies have shown that cannabis helps with migraines, which are similar to cluster headaches. One 2016 study reported a reduction from an average of 10.4 to 4.6 migraines per month in 85% of the 121 study participants. Similar results were reported by a 2019 study of 316 migraine sufferers, including the finding that high-THC cannabis was most effective.
Aside from this, numerous studies have shown that cannabis is effective at relieving pain, which is the main symptom of cluster headaches. The evidence is so strong that the National Academies of Sciences, Engineering, and Medicine concluded in their 2017 report that “There is conclusive or substantial evidence that cannabis or cannabinoids are effective for the treatment of chronic pain in adults.”
Given that relaxation is one of the most common effects of cannabis use, it may also help with restlessness: another symptom of cluster headaches.
Existing evidence shows that cannabis may help people reduce the severity and frequency of their cluster headaches, as well as pain and other symptoms. However, it may also worsen headaches in some people, so more high-quality research is needed to provide conclusive recommendations.
CBD and cluster headaches
There’s virtually no research looking at the benefits of CBD in cluster headaches. Although some researchers hypothesize that CBD could be helpful, available data shows that it is cannabis preparations high in THC—rather than CBD—that are more effective at relieving headaches.
For example, the 2019 study mentioned earlier found that cannabis with a 20:1 ratio of THC to CBD provided greater migraine relief than 1:1 preparations.
This may be because unlike CBD, THC works primarily through the cannabinoid receptors that are abundant in parts of the brain associated with headaches. Also, THC closely resembles anandamide, the endocannabinoid that seems to be most involved in headaches.
Nonetheless, it’s too early to say anything conclusive. Even if CBD is less effective at alleviating cluster headaches than THC-rich cannabis, it may still provide pain-relieving effects and help with anxiety.
How cannabis works on cluster headaches
The endocannabinoid system (ECS) exists in all vertebrates and helps regulate crucial functions such as sleep, pain, and appetite. The human body produces its own cannabinoids, which modulate and activate its various functions, but as its name suggests, the endocannabinoid system can also be modulated and activated by cannabinoids found in the cannabis plant. Because the entire system was only discovered in the past 30 years, scientists still have much to learn about the myriad ways cannabis affects the human body.
Recent research has shown that a malfunctioning ECS may be involved in headache disorders. In fact, there’s a good deal of evidence to support the theory of clinical endocannabinoid deficiency (CED), which states that insufficient endocannabinoid levels may be one of the causes of several difficult-to-treat disorders, including migraines.
Since the triggers, treatment, and biological markers of migraines are similar to cluster headaches, a dysfunctional ECS may be involved with them too.
There is evidence that this system affects three key processes considered responsible for cluster headaches.
First and foremost, researchers believe that a part of the brain called the trigeminovascular system plays a central role in causing both migraine and cluster headaches.
Endocannabinoids are known to regulate this system. For example, a 2004 study found that the endocannabinoid anandamide reduced the activity of trigeminovascular neurons. Similarly, a follow-up 2011 study reported that anandamide reduced migraine pain in rats by suppressing these specific neurons.
Second, the malfunction of the key neurotransmitter (brain chemical) serotonin is believed to be another process involved in both cluster and migraine headaches. There’s evidence that the ECS and serotonin dysfunction are related.
For example, a 2008 study found that migraine and medication-overuse headache sufferers had reduced endocannabinoid and serotonin levels in their platelets, a type of cell that may be involved in headaches.
Lastly, neuroimaging studies have consistently shown that cluster headaches originate in the hypothalamus, a part of the brain known to contain cannabinoid receptors.
More studies looking specifically at the endocannabinoid system in cluster headaches (rather than migraines) are needed. Still, current findings suggest that a malfunctioning ECS could be involved in cluster headaches, which may explain why cannabis is effective for some people.
Potential side effects of cannabis use
Although cannabis is an increasingly popular alternative to standard cluster headache treatment, it does have some unwanted side effects.
These are mostly attributed to THC, which can cause impaired memory and reaction time, increased heart rate, red eyes, dry mouth, sleepiness, and dizziness. Some people may also experience feelings of paranoia and anxiety. These side effects were noted in a 2014 study, with sleepiness and dizziness being the most common.
More importantly, six participants (22%) of a 2016 study reported that cannabis triggered or worsened their cluster headaches. It’s not clear why, but it could be related to differences in the cannabinoid content of cannabis preparations or biological differences of the users.
Another possibility is the biphasic effect: the tendency of cannabis to have opposing effects at low vs higher doses. In that sense, using a small amount might provide relief, while higher doses could make the headaches worse.
On the other hand, CBD-rich preparations lack the intoxicating side effects of regular cannabis but can cause minor issues such as diarrhea, low blood pressure (hypotension), dry mouth, lightheadedness, sleepiness, and changes in appetite. The likelihood of these effects is low unless high dosages are used.
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