There are a range of medical treatments cannabis is able to offer for illnesses not otherwise treated or which have a limited range of treatment options. Among the most exciting of these treatments are the use of cannabinoid for brain injuries. To understand what is possible through treatment, it is important to first understand the science of how cannabinoids affect the brain.
Studies show the brain levels of endocannabinoids, like anandamide and 2 AG, increase after any brain injury. This suggests our endocannabinoid system plays an essential role in compensatory repair mechanisms. Traumatic brain injury (TBI) accounts for approximately 10 million deaths and/or hospitalizations annually in the world and approximately 1.5 million emergency room visits and hospitalizations in the U.S. TBI remains difficult to treat with current available drugs and this is probably due in part to the diverse nature of pathological events occurring in the brain at the time of injury. Further, multiple causative factors lead to multiple deficits and symptoms later on like learning and memory deficits, movement disorders, seizures, other cognitive deficits, as well as significant mood problems like anxiety or depression. Survivors of TBI are at risk for lower life expectancy and are dying more than three times faster than the general population.
Our endocannabinoid system ( ECS ) is present in almost every part of our body and is especially prevalent in the brain. There are two main receptors for ECS, CB1 and CB2. CB1 is highly expressed in the central nervous system neurons (brain cells) and CB2 receptors are mainly found on the immune system cells in the brain called microglia. These receptors are also present on other peripheral nerves and immune cells throughout our body. It is the diffuse presentation of ECS which likely accounts for its ability to impact a wide variety of physiological and psychological processes like memory, anxiety, pain perception, mood and cognition, many of which are affected following a traumatic brain injury. In addition to the above-mentioned receptors, endocannabinoids also interact with other receptors involved with the release or inhibition of many other brain chemicals like serotonin, dopamine, GABA, glutamate and acetylcholine.
The mainstay of therapy for major TBI is surgery that opens up the skull to reduce the pressure building inside the brain. However, there are no drugs or medicines currently available for TBI. The initial impact produces an immediate mechanical disruption of brain tissue. This primary injury consists of contusion, damage to blood vessels, brain edema and localized brain cell death. Delayed injury mechanisms are initiated within minutes but continue over a period of days to months. Injury to the brain cells cause damage to their membranes, spilling out glutamate. This glutamate causes excessive excitation of brain cells with damage and release of reactive oxygen radicals. The injury also activates the brain immune cells (microglia), causing excessive inflammation. Damage to blood vessels also further decreases the blood supply to these areas. All of these events start a chain reaction, leading to more and more brain damage, as well as causing problems away from the brain, like lung edema.
Studies on animals reveal the efficacy of cannabinoids on brain trauma in two areas: inhibiting the chain reaction of brain cell death and decreased size of the final lesion. The level of endocannabinoids in the brain can be increased both by administering cannabis and providing enzymes which inhibit the breakdown of our endocannabinoids, hence elevating their levels. Cannabinoids, by virtue of their diverse and widespread effect, show improved outcomes in animal models of TBI. There are many additional connections to brain function that make treatment uniquely promising. Cannabinoids depress glutamate release and decrease brain cell death by excitation. Cannabinoids are also extremely potent antioxidants and work to neutralize the toxic oxygen free radicals. Cannabinoids are strong anti-inflammatory chemicals and inhibit the excessive activation of microglial and other brain immune cells, thus significantly decreasing inflammation. Cannabinoids also stabilize the blood vessels and the brain cell architecture and cannabinoids have been shown to decrease brain edema.
All these properties of cannabinoids make them a potential novel therapeutic option for TBI.