Chronic migraine is a painful and debilitating disease that affects up to 5% of the world's population. The biological mechanism responsible for migraine is not yet fully understood, but it is known to be fundamentally related to serotonin signaling. Cannabis, which also affects the serotonin system, has been shown to reduce symptoms.
The most immediate and obvious benefit of cannabis for migraine sufferers is its ability to reduce pain, which can be severe and even immobilize many sufferers. The body's own endogenous cannabinoids, such as anandamide, are believed to reduce migraine pain by regulating the input of pain signals into the brain via CB1 receptors.
It has long been known that there is a relationship between the serotonin signaling system and the incidence of migraine.
Immediately before an attack occurs, serotonin levels rise dramatically, and after the attack, they drop to lower than normal levels.
In 1985, a study was published investigating the effects of THC and CBD on the release of serotonin from blood platelets that had been incubated with plasma obtained from patients suffering from migraine episodes. It was concluded that THC, at different concentrations, had a statistically significant inhibitory effect on serotonin released from platelets.
Migraine pain is believed to be due, in part, to a complex process of widening and narrowing of the blood vessels in the skull. When blood flows through a wider section of blood vessels and reaches a section that has been narrowed, the pressure of the blood trying to flow through the channel, suddenly reduced, produces waves of intense pain. Generally, it is believed that the release of serotonin causes the larger veins and arteries to contract, while the smaller peripheral veins dilate.
Cannabis has a known vasoconstrictive effect, and its effectiveness in reducing migraine pain is believed to be partly due to this.
In the period immediately before a migraine attack, serotonin release increases. This in itself is not necessarily discernible to the individual, but several perceptible signs may be present that may indicate to the patient that an episode is about to begin, such as auras or other visual disturbances. In addition to improving symptoms for people experiencing the pain of an attack, using cannabis as soon as the initial symptoms are noticed can actually prevent the onset of migraine entirely.
Victims of chronic migraine are at risk of developing a common movement disorder, known as essential tremor (ET). TE is characterized by uncontrollable shaking, usually of the hands and arms, but sometimes affecting the vocal cords or head, and is usually made worse by attempting to use the affected body part, for example, to write or speak.
The relationship between migraine-induced essential tremor and cannabis use, there are some anecdotal reports from migraine sufferers describing how they experience subjective tremor relief after using cannabis. Additionally, much research has been done on the ability of cannabis to improve tremors in a variety of different diseases, several of which (such as Parkinson's disease) can cause tremors through biological mechanisms similar to those involved in migraine. .
Nausea is a common side effect of migraine, and it is also believed to be related to the low levels of serotonin that occur immediately after a migraine attack. Cannabis has been shown to be an effective anti-nausea remedy for a number of serious illnesses, in addition to reducing nausea experienced as a side effect of chemotherapy.