Chronic migraine is a painful and debilitating condition that affects up to 5% of people worldwide. The biological mechanism behind migraine is still not fully understood, but it is known to be fundamentally associated with serotonin signalling. Cannabis, which also affects the serotonin system, has been shown to reduce symptoms.
1. Analgesic: pain reducing
The most immediately-apparent one of all benefits of cannabis for migraine sufferers is its ability to reduce pain, which can be intense and even immobilizing in many sufferers. It is thought that the body’s own endogenous cannabinoids such as anandamide reduce the pain of migraine by regulating the entry of pain signals into the brain via the CB1-receptors.
A 2013 paper published in The Journal of Neuroscience demonstrated that sufferers of chronic migraine experience pain due to sensitization of trigeminovascular nociceptive pathways (pathways of the pain-sensing trigeminovascular nerves of the cranium); cannabinoids are known to inhibit pain responses of the trigeminovascular nerves, indicating one means via which cannabis can reduce migraine pain.
As well as the cranial nerves, CB1-receptors in the neurons surrounding the brainstem are antagonized by endocannabinoids to inhibit transmission of pain stimuli from the brainstem to other parts of the brain, ultimately providing a dual benefit to individuals experiencing migraine.
2. Serotonin inhibitor
It has been known for some time that there is a relationship between the serotonin signalling system and the incidence of migraine. Immediately prior to an attack, serotonin levels increase dramatically, then fall to below-normal levels following the attack.
In 1985, a study was published investigating the effects of Δ9-THC and CBD on serotonin release from blood platelets that had been incubated with plasma obtained from patients undergoing episodes of migraine. It was concluded that Δ9-THC at various concentrations had an statistically significant inhibitory effect on serotonin released from the platelets.
Conversely, plasma obtained from patients during attack-free periods showed no inhibitory effect on serotonin release, despite being treated with Δ9-THC at the same concentrations. Furthermore, CBD showed no significant inhibitory effect either on plasma from attack-free periods or from attack periods.
This study, and various similar studies that have been conducted since then demonstrate that cannabis Δ9-THC inhibits serotonin release during migraine attacks but not in migraine-free periods, and that CBD has a negligible effect in either situation.
It is thought that the pain of migraine is partly caused by a complex process of widening and narrowing of blood vessels in the cranium; when the blood flows through a wider section of blood vessel then meets a narrowed section, the pressure of the blood attempting to flow through the suddenly-reduced channel cause waves of intense pain. Generally, it is thought that serotonin release causes the larger veins and arteries to become constricted, while the smaller peripheral veins become dilated.
Due to this, vasoconstrictor drugs (drugs that narrow the blood vessels) are often used in the treatment and prophylaxis of migraine, as the likelihood of pain is reduced if the dilation effect does not happen. Cannabis has a known vasoconstrictor effect, and it is believed that its efficacy at reducing migraine pain is partly due to this.
In the period immediately before a migraine attack, serotonin release increases. This is itself is not necessarily discernible to the individual, but there are several discernible signs that may be present that can indicate to a sufferer that an episode is about to commence, such as auras or other visual disturbances. As well as improving the symptoms of individuals experiencing the full pain of an attack, if cannabis is taken as soon as initial symptoms are noticed, it may actually prevent the onset of migraine entirely.
As previously mentioned, imbalances in serotonin levels are associated with onset of migraines, and it has been variously demonstrated that there is a relationship between the endocannabinoid system and the serotonin signalling system, and that use of cannabinoids can lead to a reduction of serotonin levels. As serotonin release increases immediately prior to a migraine, use of cannabinoids at this point may inhibit the abnormal increase and prevent the resultant processes that lead to the generation of migraine.
5. Anti-tremor benefits
Sufferers of chronic migraine are at risk of developing a common movement disorder known as essential tremor (ET). ET is characterized by uncontrollable shaking, typically of the hands and arms but occasionally affecting the head or vocal cords, and often becomes worse if attempting to use the affected body part, e.g. for writing or talking.
While there have been no studies specifically investigating the relationship between migraine-induced essential tremor and cannabis use, there are some anecdotal reports of migraine sufferers experiencing subjective relief from tremor after using cannabis. There is also abundant research into the ability of cannabis to improve tremors in a range of other conditions, several of which (such as Parkinson’s) may cause tremors via similar biological mechanisms at work in migraine.
Again, it appears that the serotonin signalling system may have a fundamental role to play in the manifestation of tremor symptoms, in Parkinson’s and related conditions as well as in chronic migraine. Specifically, it appears that low serotonin is often associated with tremors; while cannabis may inhibit serotonin release from the platelets in cases of migraine, it has also been shown to induce synthesis of serotonin in other studies, so it may have a role to play in raising serotonin to normals levels in individuals suffering from depleted levels.
6. cannabis as an Anti-nausea remedy
Nausea is a common side-effect of migraine, and is also thought to be associated with depleted serotonin levels immediately following migraine attack. Cannabis has been demonstrated to be an effective anti-nausea remedy for various serious conditions, as well as lessening the nausea experienced as a side-effect of chemotherapy.
While there have been no specific studies into the ability of cannabis to manage migraine-induced nausea, there are numerous anecdotal reports of patients self-medicating with cannabis and experiencing subjective relief. There are also various other conditions in which excess serotonin can cause nausea that can be managed by cannabis; for example, cancer patients undergoing chemotherapy that experience nausea due to excess serotonin irritating the gastrointestinal tract.